BotroKienthucLuyenthiDaihocTrenkenhVTV2VatlyPhan2DienxoayChieu p5

fe>' trpklen

thiic

trSn hciili

V^t It LTBH

VTV2.

l.jp J

Huong

(liu

Vdn

BI6n

MTV O vvil

Cty Tniltl

dan

KbangVlft

d u 11* N g u a i ta can tai d i m o t cong sua't 1 M W t u nha may dien ve n o i tieu
thu. D u n g hai cong ta dien dat 6 bien the'va 0 dau n o i tieu t h u thi tha'y so'

^ AP
PR
n =
= —^
P

•2-772

..„,

U2

=>Chon D.

chi cua c h u n g chenh lech m o i ngay d e m 216 k W h . T y le hao p h i d o chuyen

h2 = h i . ^ = 4,8%
^
' U

p
PR

.

•

tai dien n a n g la

^ :.-q>'.'''^r

• ^ : snx '

A. 0,80%.


/ i d u 9: N g u o i ta t r u y e n tai dien xoay chieu m o t pha \.\x m o t t r a m phat dien
d e n n o i tieu t h u bang day dan c6 tong chieu dai 20 k m . D a y d a n l a m bang
kirn loai c6 dien t r o suat 2,5.10'^ Q m , tiet dien 0,4 cm^, he so cong suat cua
mach dien la 1 . D i e n ap h i e u d u n g va c o n g suat t r u y e n d i o t r a m p h a t
d i e n la 10 k V va 500 k W . H i e u suat t r u y e n t a i dien la
A . 93,75%.

B. 96,14%.

>: ..-,...5)

C. 97,41%.

V

j , ^f,,/^

R = p-^2,5.10-^

=12,5(Q)

U"cos>

,

P

:.

cong suat 200 k W . H i e u so chi ciia cong to 6 t r a m phat va cong to tong 6 noi
tren d u o n g day va hieu sua't cua qua t r i n h t r u y e n tai dien Ian l u g t la
A. 100 k W ; 80%.

A P . ^ =l
At
•Chon C.

=> C h o n A .
-/iii y: Khi cho hieu suat truyen tai va cong suat nhan dugc cuoi duang day thi tinh
P'
H =—^P
P

;,

V i d u 12: D i e n n a n g 6 m o t tram phat d i e n d u g c t r u y e n d i d u o i d i e n ap 2 k V va

B. 83 k W ; 85%.

C. 20 k W ; 90%.

Huang

10000^1

dugc cong suat dua Icn du'ang day, cong suat hao phi trcn duang

.^,-J:^,y, : \. 0,95%.

" :
Huong dan
>
AA
216kWh
,
AP
9kW
AP = — = — —
= 9 ( k W ) => h = —
= 0,9%
24 h
At
lOOOkW
=> Chon C.

fi-J

U^cos>

C. 0,9%.

tieu t h u sau m o i ngay d e m chenh lech nhau 480 k W h . C o n g sua't hao p h i

D . 96,88%. , ; , f

Huangdan

B. 0,85%.

day:

? ^
24h

= 20(kW)^H =:

D . 40 k W ; 95%.

dan
^

=^

^
200

= 90%

PR
CM y: Hieu sunt truyen frt/ h = 1 - H = • „
thay dot bang thay doi dien dp,
U^cos^cp
dien tra, cong suat truyen tai.

P'
p2
APII^
= —;AP = (1-H)P;AP = —yR=>R =
H
^
'
P

d y 10: T u m o t may phat dien n g u a i ta m u o n t r u y e n t a i n o i tieu t h u , bMng

Thay d o i U :

PR
h i ^ l - H i ~
U f cos^ (p
h,

d u o n g day tai dien c6 dien t r o 40 Q va h^ so'cong suat b a n g 1 . Biet hieu

PR

=1-H

\2

I-H2
1-H,

^"U^cos^cp

sua't t r u y e n tai la 98% va n o i tieu t h u nhan d u g c cong sua't dien 196 k W .
h

D i e n ap hieu d u n g d u a len d u o n g day la
A. l O k V .

B.20kV.

C. 40 k V .
Huangdan

H - ^ =i. 0,98 =

D . 30 k V .
' • '' '

:^ P = 200(kW)

AP = ( l - H ) P = 4 ( k W )
p2

Thay d o i P:

,

R^
^ 4 .. 1100- -^
AP = -•^^R

.

(200.10^]
^

• ,h
2

" '

hi - l - H j - - 2
2P,R
h , = 1 - H , =•U cos (p
cos^ (p

1; Thay d o i R;

^'t^Ju

U^cos^cp

h , = 1 - H , =•
.40

=> U = 20.10^ ((VV))

V'i

PR,

1-H2
1-H1

1-H2_R2
I-H1

di

Ri

cos^ (p

d i i 13: N g u o i ta t r u y e n tai d o n g dien xoay chieu m o t pha t u nSa m a y dien
den n o i tieu t h u . K h i dien ap 6 nha may d i ^ n la 6 k V t h i h i ^ u suat t r u y e n tai
V la 73%. De hieu sua't truyen tai la 97% t h i dien ap a nha m a y d i e n la

AA
"hii y: Ncu trong thai gian At dim nang hao phi AP: AP =
.

H

hi = 1 - H , =

=> C h o n B.

40

-1

-""^-^f-

'A.24kV.

B.54kV.

C. 16 k V .

D. 18kV.
241


Bo trp Men thurc V^t li LTOH tren kenh VTV2. tigip 2 - Chu Van Bten

Huong
PR

hi=l-H,=

h, = 1 - H ,

iv; '

cos^

2 . 1-0,97 _

1 -H2

(p

^

U2 cos^

r

R2 _
R,
1^2;

1

R=P3=P

7r(0,5df

6 ^

IU2J

* 1-0,73

PR
=

Huang
2

dan

dan
2 . ;,

!'„> >'/)•

.3j

hi=l-H,=

(p

=^U2=18(kV)

U^cos>

l - H ;

R2

I-H2

PR-

1-Hj

Rj

1-0,91

h2=l-H, =

_(2^

=>H2 =0,96

U^cos^q)

Chon D .

n^ChonA.

V i d u 14: Xet t r u y e n tai dien tren mot d u o n g day nlia't d j n h . N e u dien ap
t r u y e n tai dien la 2 k V t h i hicu suat truyen tai la 80%. N e u tang dien ap

V i du 17: M o t nha m a y phat dien g o m 4 to may co c u n g cong suat P hoat d o n g
d o n g t h a i . D i e n san xuat ra d u g c dua len d u o n g day va t r u y e n de'n n o i tieu

t r u y e n tai len 4 k V thi hieu sua't truyen tai dat
A . 95%.

B.90%.

.

,

C.97%.

Huong

.

thu v a i hieu sua't t r u y e n tai la 80%. K h i m o t to m a y n g u n g hoat d p n g thi

D . 85%.

hieu sua't t r u y e n tai k h i do la

dan

A . 90%.
h,=l-H,=PR
h, = 1 - H , =
^ U2 cos^

2

1-H2

C O S ^ (p

1-H1

^1-H2^

lU2.

B.85%.

2
r^H2

1-0,8

Huong dan
hi=l-Hj=

.4.

h, = 1 - H ,

.0 rj^>d:.

'

I-H2

tieu t h u la 35%. D u n g may bien ap l i t u o n g co ti so gii>a cupn t h u cap va
cuon so cap la N 2 / N 1 = 5 de tang dien ap t r u y e n tai. H i e u suat t r u y e n tai sau

B. 97,4'X..

' ' " C . 45,7%.
Huong

D . 32,8%.

Ptu

y: Phan

bict hai

3

truvng

hop: cong suat dim len duong

klidc vol

tnixrng

hop

suat nlian dugc cuoi

dan

l - H ,

cos^ cp

day kliong dot (P = const)

k h i su d u n g may bieh a p l a

P2

=

V i d u 15: H i e u suat t r u y e n tai d i e n nang mot cong sua't P tir m a y phat de'n noi

' A , 99,2%.

'^l
'Al\'.n,vy

(p

'

^ Jit

=0,95
U^cos>

=>ChonA.

C.75%.

10-25 g

lP

P' =

= UlCDB.

P-AP

cong
duong

day khong den (P' = const).
• Theo bai ra:

V i du 18: D i e n n a n g can t r u y e n tai tu noi phat dien de'n n o i tieu thu dien. Coi

= —^ = 5

rang tren d u o n g day truyen tai chi co dien tro R k h o n g d o i , coi d o n g dien
PR
h l = l - H l = ,,2

2

UtC0S>

h, = 1 - H ,

^

=

PR

^1-H,

1

1-H2

1 - H ; _

~ VU2

1-0,35

t r o n g cac mach l u o n ciang pha v o i dien ap. L a n l u o t dien ap d u a len la U i
H , =0,974

{5J

U2 COS^ (J)

va U 2 t h i h i ^ u suat t r u y e n tai t u o n g l i n g la H i va H 2 . T i m t i so U2/U1 trong
hai tru'ong h o p :
a) cong sua't d u a len d u o n g day khong doi;

Chon B.

' '

b) cong sua't n h ^ n d u o c cuoi d u a n g day k h o n g d o i .

V i d u 16: Can t r u y e n tai cong sua't dien va dien ap nhat d i n h t u i.ha may ^1^';
noi tieu thu bang day dan c6 d u o n g k i n h day la d. Thay the'day truyen t'^'

Huong dm
A p dyng cong thuc: h = 1 - H

—

'
;•

;

d i e n ' b a n g m o t day khac c u n g chat lieu n h u n g co d u o n g k i n h 2d t h i hi'^^'
sua't tai d i e n la 9 1 % . H o i k h i thay the'day t r u y e n tai bang loai day cijng cli'''|
lieu n h u n g co d u o n g k i n h 3d t h i hieu sua't t r u y e n tai d i e n k h i do la b'^'

- H =

PR
U^'os^cp

nhieu?
A.96%.

I) h = l

B.94%.

C.92%.

"

P . 95%.

I-H2

PR
•2::;.
_ U | c o s2:>

1-H

1-H2
Ujcos cp
24^


Bd

trg

kiSn

thtic

V$t

It LTOtI

tr6n

kgnh

VTV2.

t^p

b) Thay P = P'/H vao cong thuc h = 1 - H =

>(1-H)H =

P'R
U^cos^cp

2 - Chu

Vdn

Blgn

PR
P'R
^ ta du"oc: 1 - H =
HU^cos^
U cos cp

( 1 - H 2 ) H 2 _ U^cos^(p _
P'R
"(l-Hi)H, "
2
'l'

H i e u suat t r u y e n tai dien sau do (P' g i u nguyen con AP' =
H, =

P'+AP'

P'+

P'
1900

1901

Ap d u n g :
U2 _

(l-H,)Hj

_

(1-0,95)0,95

U]Cos (p

1900"i 1900

Lai khuyen: Den day ta nen nha hai ket qua quan trong de giai tiCv cdc hai todn

phicc tap hon:
7. Khi P khong doi thi

^

1901J1901

bao nhieu Ian de g i a m cong suat hao p h i tren d u o n g day tai dien n Ian, v o i
{l-Hi)Hi

dieu kien cong suat truyen den tai tieu thu k h o n g doi? Biet rang k h i chua

(1-H2)H2

tang dien ap d o g i a m dien the tren d u o n g day tai dien bang x U ( v o i U la

d i e n n o i tieu t h u k h o n g d o i , bSng mot d u o n g day nhat d j n h . N e u dien ap

dien ap hieu d u n g giira hai cue cua tram phat dien). Coi c u o n g d p d o n g
dien t r o n g mach l u o n cung pha v o i d i e n ap dat len d u o n g day.
Huang dan

dua len d u o n g day la 3 k V thi hieu suat tai dien la 75%. De hieu suat tai
B.5,96kV.

CSVskV.

D . 15 k V .

Hwang dan
Ap d u n g :

^

1

(l-Hi)Hi

V(1-H2)H2

U2
3

hi=l

1(1-0,75)0,75
^(1-0,95)0,95

Chii y: Neu cho biel do giam the tren duang day ta tinh dugc hieu suat truyen tai:
UIcoscp

U

I

P' = H i P = ( l - x ) P = > P =
^
„
AU
(1-x)
-H. =
= x

'
U
AP = h j P =
-P'
1-x

cos(p

P'
H , =•
P'+ AP'

I f , 111

' '

J'(;.(!'
11

H i e u suat t r u y e n tai dien sau do (P' giir nguyen con AP' =

U2 « 5 , 9 6 ( V ) =^Chon B.

P

^ ^

H i e u suat t r u y e n tai dien trong t r u o n g hop d a u :

dien 95% t h i dien ap dira len la

A.3kV.

Chon D .

V i du 21: D i e n ap hieu d u n g giua hai cue cua m o t tram phat dien can tang len

V i du 19: Can t r u y e n tai dien t u nha may den nai tieu t h u sao cho cong suat

'

= 9,505 ^ U2 = 9,505Ui

Chii y: Dethn ra cong thicc dep ta giai bdi todn tong qiidt han.

1-Hi

1

Khi P khong doi thi U2

1900

1900

P'

P'

P'

AP
100

AP
n

n(l-x)

P'):

n(l-x)
n(l-x) + x
n(l-x)

V i dy 20: D i e n ap hieu d u n g giiia hai cue ctia mot tram phat dien can tang len
bao nhieu Ian de g i a m cong suat hao p h i tren d u o n g day tai dien 100 Ian,
v o i dieu kien cong suat truyen den tai tieu thu k h o n g doi? Biet rang khi

Ap d u n g :

Hi-

Ui "\((1-H2)H2

1_

7^

n(l-x)
n ( l - x ) + x^ n ( l - x ) + x

chua tang dien ap do g i a m d i ^ n the tren d u o n g day tai dien bSng 5% dien
ap h i f u d u n g giiia hai cue ciia tram phat dien. Coi cuong d o d o n g dien

n(l-x) + x

x(l-x)

0-Hi)Hi

V i du 22: D i e n ap hieu d u n g giua hai cue ciia m o t tram phat d i e n can tang len

t r o n g mach l u o n cung pha v o i d i ^ n ap dat len d u o n g day.

bao nhieu Ian de giam cong sua't hao p h i tren d u o n g day tai d i e n n Ian, v o i

A . 8,515 Ian.

dieu kien cong suat truyen den tai tieu thu k h o n g doi? Biet rang k h i chua

B. 9,01 Ian.

C I O Ian.

D . 9,505 Ian.

tang dien ap do g i a m dien the tren d u o n g day tai dien bang x U ' ( v o i U ' la

Huang dan

dien ap hieu d u n g n o i tai tieu thu). Coi cuong dg d o n g dien t r o n g mach

H i f u suat t r u y e n tai d i ^ n trong t r u a n g h o p dau:
y

u

= H i P = C,95P=>P=

H i = 0 , 0 5 = > H i =0,95<
A P - h i P = 0,05P =

^

^
0,95

l u o n cung pha v a i dien ap dat len d u o n g day.
.

Huang dan

H i e u sualt t r u y e n tai dien trong t r u o n g h a p d a u :

, , :
' >•
M; '.; 1 a', •
245

tid itp klStt ihat:

11 tttJti

h, = 1 - H i =

AU
U

i.ip

tr€n k&nh VTVJ
AU

X

U'+AU

x +1

'/

s lui van

P' = H i P =

AP

BISti

1

H i e u sua't t r u y e n tai sau do (P' giCr nguyen con AP' =

x +1
AP = h i P = xP'

_

U2_

(l-Hi)H,

1

V(1-H2)H2

Ui

1~

+ X

1+

n
n +

X

n +

X

n
n +

(1

Ap

Gia sir he so cong suat n o i tieu thu bang 1 . De hao p h i t r u y e n tai giam di
100 Ian so v o i t r u o n g hop dau thi dien ap dua len d u o n g day la

A p d u n g : ^2 _
]

n+X

( l + x)>/n

•

=> C h g n B.

a-.

U,

kn

kn + x

kn
X

[T

(k + x ) V n

J kn + X

tai tieu thu k h o n g doi? Biet r§ng khi chua tang dien ap do g i a m dien the
tren d u o n g day tai dien bang 10% dien ap hieu d u n g tren tai tieu t h u . Coi
c u o n g do d o n g dien t r o n g mach luon cung pha v o i dien ap dat len d u o n g
day.
B. 9,5 Ian.

^

• ^

Ui

2 + 0,1

,

may ha the If f u o n g c6 ti so v o n g day N1/N2 = k va cuon t h u cap noi v o i tai
tieu t h u . D i e n ap hieu d u n g giua hai cue ciia m o t trcim phat dien can tang

CO tieu tliu.

-^-n^-^r:

,

.

•

• •

1

1
(CT)

cong to thi sochi cm cong ta
nang ma dong

• ?

VlOO

Chu y: Klii dong ca dim mac sau
chinh la dim

D . 9,3 Ian.

Huangddn''

(k + x ) V n

=>ChonB.
nsii.4.

C. 8,7 Ian.

-

]^.^J-J-^^^ni.9,5

Apdung:

9:;,
nS'(iJ'J*

k +x

k + x

^_

y(l-H2)H2

hao p h i tren d u o n g day tai dien 100 Ian, vai d i r u kien cong sua't t r u y e n den

'

Jivyu^j^ u i ^ t.i '>t: i;i.,<: vi'Mh-'Sit

U^'-i ; ' U

... ,

(l-Hi)H,

-

V i d u 24: T r o n g qua t r i n h t r u y e n tai dien nang d i xa, a cuol d u o n g day cfung

" '

1

,

'

- . • = y}

'•

(^P^Uai
_I____J

I,R

'J''

len bao nhieu Ian de g i a m cong sua't hao p h i tren d u o n g day tui dien n Ian,

V i d u 26: M o t d u o n g day dan g o m hai day c6 tong dien t r o R = 5 Q dan d o n g

voi dieu kien cong sua't t r u y e n den tai tieu t h u k h o n g doi? Eie't rang k h i

dien xoay chieu de'n cong to dien. M o t d o n g co dien c6 cong sua't co hoc

chua tang dien ap do g i a m dien the tren d u o n g day tai dien bang xUt,,i ( v o i

1,496

Ut.ii la dien ap hieu d u n g tren tai tieu thu). Coi c u o n g do d o n g dien trong

d o n g C O boat d o n g b i n h t h u o n g va dien ap hieu d u n g g i i i a hai dau cong to

mach l u o n cung pha v o i dien ap dat len d u o n g day.

bang 220 V. T i n h c u o n g do hieu d u n g ciia d o n g dien t r o n g d u o n g day tai

Huong

,
, „
AU
AU
AU
hi = 1 - H j =

=
=
p.,.. .
U
U'+AU
kUi.-+AU
P' = H i P =

k +:

AP = h i P = - P '
k

-P

.p = i ^ P '
4v

k W CO he so cong sua't 0,85 va hieu sua't 80% mac sau cong to. Biet

dien. D o n g co hoat d o n g trong thai gian 5 h t h i cong to chi bao nhieu kWh?

dan

H i e u sua't t r u y e n tai dien trong t r u o n g hgp dau:

246

U^^

dung:

A. 10,0 Ian.

'

^ ^ 100, X = 0,1 ta d u g c U2 = 9 , l U i . ' '

M a U i = U + 0 , l U = l , l U n e n U 2 = 10,01U

kn + x , ,fwHAi^£ - f / i j c . c . - O i

may ha the l i t u o n g c6 ti so v o n g day bang 2. D i e n ap hieu d j n g giiia hai

hieu d u n g giua hai dau tai la U t h i do giam the tren d u o n g day bang 0,1U.

Huong dan

,! (do

cue cua m o t tram phat dien can tang len bao nhieu Ian de g i a m cong sua't

X

D . lOOU

kn

Vi d u 25: T r o n g qua t r i n h truyen tai dien nang d i xa, 6 cuo'i d u o n g day d u n g

X

+ X)NA^

C.9,1U.

_

kn +

thu, cong suat n o i tieu thu (tai) l u o n d u g c g i u k h o n g d o i . K h i hieu dien the

B. 10,01U.

P'
kn

vi d u 23: T r o n g qua t r i n i i truyen tai dien nang t u may phat dien den noi tieu

A.20,01U.

^

' P'+AP' ~ p . + X p .

,
AP
X
H i e u sua't t r u y e n tai dien sau do (P' g i u nguyeh con AP' = — = — P ' ) :
n

n
P'
P'
n
H, =
P'+ AP' P'+ " P '
n

fi A p d u n g :

r*'

X

= -;—P'):

T i m dien nang hao p h i tren d u o n g day tai t r o n g 5 h .
Huong

X

flrioiP •

dan

C o n g sua't tieu t h u dien:
k+x

P

P =i l
H

P

1 AQf^ 10

UIcoscp : ^ 220.1.0,85 = '
^ H
0,8

=:> I - 1 0 ( A ) ; , s : n
hVi
. ;^ ;

So chi ciid cong to c h i n h la dien nang ma d o n g co tieu t h u : "'^'^

',
247


0,8

V i du 29: D i e n nang d u g c t r u y e n tai t u A den B bang hai day d o n g c6 dien tro

( W ) 5 ( h ) = 9350(Wh) = 9,35(kWh)

tong cong la 40 Q. C u a n g do hieu d u n g tren d u o n g day tai dien la 50 A ,

D i e n nang hao p h i tren d u o n g day sau 5 h:

A A = APt = l2Rt = 1 0 l 5 . 5 ( h ) = 2 5 0 0 ( W h ) = 2,5(i
cong suat tieu hao tren day tai dien bang 5% cong suat d u a len d u o n g day d
A . C o n g suat d u a len d A la

j

Chu y: Nha may phdt dien c6 cong siiat Pmp va dim dp Umr tritac khi dim len dubng

A. 2 0 k W .

dp dim len diamg day Ian luvt Id:

u = ump

C. 2 M W .

Huang

day dctdi dien di xa ngiivi ta dimg may tang dp co hieu sunt H . Cong sud't vd dien
Theo bai ra:

P = PmpH

,,,(

B. 2 0 0 k W .

D . 2000 W .

dan

,

,„ v

, . ^ „^

AP = 5 % P = > I ^ R = 0,05P=> 50^.40 = 0,05P

N.

=>P = 2 . 1 0 ^ ( W ) = > C h o n C .

' '

•

"

"

V i du 27: M o t may phat d i e n xoay chieu cong suat 10 ( M W ) , d i e n ap giua hai

V i du 30: D i e n nang d u g c t r u y e n tai t u A den B bang hai day c6 he so cong

cue may phat 10 ( K V ) . T r u y e n tai d i e n nang t u nha m a y dien den n o i tieu

suat bang 0,96. C o n g suat tieu hao tren day tai dien bang 5% cong suat dua

thu bang day dan c6 tong dien tro 40 (CI). N o i hai cue m a y phat v o i cupn so

len d u o n g day 6 A . N e u d i e n ap dua len d u o n g day la 4000 V t h i do giam

cap cua may tang the con noi hai dau cuon t h u cap v o i d u o n g day. So vong

the tren d u o n g la

day cua cuon t h u cap cua may bie'n ap gap 40 Ian so'vong day ciia cuon so

A . 20 k V .

B. 200 k V .

' "" '

' f , )

Huongd^n

cap. H i e u suat cua may bie'n ap la 90%. Bie't he so' cong sua'i d u o n g day
B. 20,15 k W .

C. 20,25 k W .
Huong

U = UMV—

^2 _ i n i n 3

.

<:>I^R = a % U I c o s ( p < ^ I R = a%Ucos(p

dan

o

^ ->r,5,

= 10.10^.40 = 4.10^' ( V )

'

D . 192 V .
:

. ,

'.jSil/ ly'l

V/:,;
; •
..; ]!!:, : •

../iX;';:

'"•fim^'M

A U = a%Ucos(p ^ A U = 0,05.4000.0,96 = 1 9 2 ( V )

=>ChonD.

= lO.lO^.gO'X. - 9.10^' ( V )

.,

,

'

V i du 3 1 : D i e n n a n g d u g c t r u y e n tai t u A den B bang hai day d o n g c6 d i f n t r o
tong cong la 5 Q. C u o n g do hieu d u n g tren d u o n g day tai dien la 100 A ,

V i du 28: M o t t r a m phat d i e n t r u y e n d i cong suat 1000 k W bang day dan c6
d i e n t r o t o n g cong la 8 Q, d i e n ap 6 hai cue cua may la 1000 V H a i cue cua
m a y d u g c n o i v o i hai dau cuon so ca'p cua may tang ap l i t u o n g ma so'vong

cong suat tieu hao tren day tai dien bang 2,5% cong suat tieu Hiu 6 B. T i m
cong suat tieu t h u 6 B.
A.20kW.

day cua cuon t h u cap gap 10 Ian so v o n g day cuon so cap. Bie't he so cong
suat cua d u o n g day la 1. H i e u suat qua t r i n h t r u y e n tai la :
A . 80%.

I

-;i,.aOir[;Mn

^

D . 20,35 k W .

AP = ^ R = » 2 0 , 2 5 ( k W ) = > C h o n C .
P = PMP'H

.
I

Theo bai ra: AP = a % U I cos m

b a n g 1. Xac d j n h cong suat hao p h i tren d u o n g day.
A . 20,05 k W .

'I'

C. 2 M V .

B. 87%.

C.92%.
Huang

D . 95%.

;•:

B.200kW.
•A', s i v : , . . j i ,

C. 2 M W .
Huang dan

I^R = 0,05PB => lOOls = 0,05.Pu => Pg = 2.10" ( W )

D . 2000 W . ,
AJO I

A -

::^#« MfciU-;vW*;»,::{6,t>,.-

;. ;.
•

= > C h o n C . X' .

dan

Chu y: Neii noi tieu thu diing may ha dp vd cong suat hao phi tren duang day bang if/o
U-U

= 1000.10 = 1 0 ' ' ( V )

PR
H =l - h = l--

10^8

= 92%

10*^

P = P„pH = 10''(W)

cong sud't tieu thu tren
tai thi:
I?R = a%U2l2Cos(p2

r^ChonC.
Chuy:

I,
'

"

lj|

1) Neil cho biel cong siiat hao phi tren duong day bang a% cong suat am len duong
day thi AP = a%P

I^R = a%UIcos(p o IR = a%Ucos(p o

A U = a%Ucos(p

2) Nell cho Met cong siid't hao phi tren diivng day b^ng «% cong suat suat nhan dugc
cuo'i dudng day thi AP =
248

a%P'.

R

l2COS(p2

Dien dp dua len duang day: U = U , + A U = U , + I , R

V'!

V i du 32: N g u o i ta t r u y e n tai dien nang t u A den B b i n g he t h o n g day dan t u
CO d i e n t r o 5 Q t h i c u o n g do d o n g dien hieu d u n g tren day la 60 A . Tai B
d u n g m a y ha t h e ' l i t u o n g . Cong suat hao p h i tren day bang 5% cong suat
249


Wi l,a hicn

V^t n LIVII

Ih'it

lien

HBlin

VMVJ,

IJI/J

tieu thu a B va dien ap a cupn t h u cap cua may ha t h e c o gia trj hieu d u n g

d u 3 5 : D i e n nang d u g c t r u y e n t u may tang ap dat tai A t o i may ha ap dat tai

la 300 V l u o n ciJng pha v o i d o n g dien qua cuon t h u cap. T i so so v o n g day

B bang day d o n g tie't dien tron d u d n g k i n h 1 cm v o i tong chieu dai 200 k m .

ciia cuon t h u cap va so cap cua may ha the la

C u o n g d o d o n g dien tren day tai la 100 A , cac cong sua't hao p h i tren d u o n g

A. 0,01.

B. 0,004.

C. 0,005.

- '

Huong dan

•

D . 0,05.

day tai bang 5% cong sua't tieu thu 6 B. Bo qua m o i hao p h i t r o n g cac may

' * '•

bien ap, coi he so cong suii't cua cac mach so cap va t h u cap deu b3ng 1, dien
fro sua't cua d o n g la 1,6.10-''' Q m . Dien ap hieu d u n g 6 may t h u cap cua may

Theo bai ra:
i f R = a % U 2 l 2 cos(()2
N2

11

U2
= — ^ =

N,

U1

A . 43

60

N2

!

tang ap 0 A la

6 0 l 5 = 0,05.300.12-1 => I2 = 1 2 0 0 ( A )

r=>—i- =

I2 cos(p2

N,

=^ChonD

= 0,05

J . .

1200.1

^f,il'\H-M'4hA

'

-Hhibi

.nwirii

'

ir\f(\T

•5

kV.

B. 42

kV.

C. 40 k V ;

" ^i''"'

D . 86

kV.

•••

; *^f •

-muh :;mm\Kn(.lM.

tai dien m o t pha c6 dien tro R = 30 Q. Biet dien ap hieu d u n g a hai dau cuon

K(o,5d)2

s

'

/ i d u 3 3 : Dien nang d u g c tai tu tram tang ap toi t r a m ha ap bang d u o n g day

A P = 5%PB ^

K(o,5.o,oi)2

I ? R = 0,05U,I,

^ '

^

,,

.

,:.,

'"

'

so cap V a t h u cap cua may ha ap Ian l u g t la 2200 V va 220 V, c u o n g do dong
dien chay t r o n g cuon t h u cap cua may ha ap la 100 A. Bo qua ton hao nang
l u g n g 6 cac may bien ap. Coi he so cong sua't bang 1. Dien ap hieu d u n g o
hai dau cuon t h u cap cua may tang ap la

Dien ap hieu d u n g 6 may t h u cap cua may tang ap d A :

,

U = U , + I , R = 82.10^ +100.41 = 4 3 0 5 0 ( V ) * 8 6 ( k V )

^^-H^^^^

=^ChonD.
A. 2200 V.
Ui

B. 2500 V.
2200

I2

U2 _ I i

220

_

100
I,

C. 4400 V.

D . 2420 V.

•r:>I, =10(A)

Vi d u 3 6 : ( D H - 2012) T u mot t r a m phat dien xoay chieu m o t pha dat tai v i t r i

,Via;t£«i

. ,

.(jfiodD-

U = U , + A U = U , + I i R = 2200+ 10.30 = 2500(V)

j^rifo gaoi

A, :.

=>ChonB.

M , dien nang d u g c t r u y e n tai den n o i tieu thu N , each M 18O k m . Biet
d u d n g day c6 dien tro tong cong 80 Q (coi day tai dien la d o n g cha't, c6 dien
tro ti le thuan v o i chieu dai cua day). D o su co, d u o n g day bj ro d i e n tai
die'm Q (hai day tai dien bj noi tat boi m o t vat c6 dien t r o c6 gia trj xac d i n h

Vi d y 34: C u o n so cap cua may tang the A dugc noi v o i nguon va B la may ha

R ) . De xac d i n h v i t r i Q, truoc tien n g u o i ta ngat d u o n g day k h o i may phat

the CO cuon so cap noi voi dau ra cua may tang the A. Dien tro tong cong cua

va tai tieu t h u , sau do d u n g nguon dien k h o n g d o i 12V, dien t r o t r o n g

day noi tir A den B la 100 Q. M a y B c6 so v o n g day cua cuon so cap gap 10 so

k h o n g dang ke, noi vao hai dau cua hai day tai dien tai M . K h i hai dau day

v o n g day cua cuon t h u cap. Mach t h u cap cua may B tieu thu cong sua't

tai N de h o t h i c u o n g do d o n g dien qua n g u o n la 0,40 A , con k h i hai dau

lOOkW va c u o n g do hieu d u n g 6 mach t h u ca'p la 100 A . Gia su ton hao cua

day tai N d u g c noi tat boi m o t doan day c6 d i e n t r o k h o n g d a n g ke thi

cac may bien the 6 A va B la khong dang ke. He so cong sua't tren cac mach

c u o n g d o d o n g dien qua n g u o n la 0,42 A . Khoang each M Q la

deu bang 1 . Dien ap hieu d u n g 6 hai dau mach t h u ca'p cua may A la

A. 135 k m .

A.llOOOV.

B. 10000 V.
;;„X.. <

.

".c-,;i«il!o

C. 9000 V.

Hu'migddn

.

^
= l l ^ l , = l 2 . ^ = 1 0 0 . - = 10(A)

N,
I2—i^.^
N,
10
Pi = P2 =^ U i l i = P2 ^ U i . l O = 100.10^

>ifi i

clJ

ft)j«{ j i f i >.f

250

I.

idq

triu?,

.vjinwuJ

ti

,: t •

m/fif^M)

(;d

gntib

-tfii

R =

— = 30(Q)

I
=i'R=30-2x

U i = 10* ( V )

,.^,

\Bm

D . 90 k m .

K h i dau N de ho, d i e n t r o cua mc^ch:
2x +

U = U i + A U = U i + I i R = 10^+10.100 = 11000(V)
fl , => Chon B.

C. 45 k m .
Hitdiigdan

„^r'^

, _

MdyB:

B. 167 k m .

D . 12000 V .

^ '

'

"
X

*

K h i dau N noi tat, dien tro cua mach:

^

2x+

•

^-(-"-^-^ =M.^(Q)
R + (80-2x)
I
7 ^ '

40-x

*
^

*

R

N
40-x

251


Cty TNHtt nrv D vvn Hhang Vtft

no-4x
=> MQ =-J^MN = 45(km)

7

B A I T A P D|NH TINH

Chon c.

V i du 37: Mot duong day tai dien gii>a hai diem A, B each nhau 100 km. Dien
tro tong cong cua dirong day la 120 Q. Do day each dien khorg tot nen tai
mot diem C nao do tren duong day c6 hien tugng ro dien. De phat hien vi
tri diem C ngudi ta dung nguon dien c6 sua't dien dong 41 V, dien tro trong

IQ. Khi lam doan mach dau B thi cuong do dong dien qua nguon la 1,025A
Khi dau B ho thi cuong do dong dien qua nguon la 1 A. Diem C each dau A
mot doan
A. 50 km.

B. 30 km.

C. 75 km.

"> D. 60 km.

Humg dan
De hd dau B : 2x + R + r = y = 41Q => R = 40 - 2x
Doan mach d^u B : 2x + R + (120-2x)
+
>2x +

(40-2x)(100-2x)
160-4x

=> AC =

60

Ck\i 1= Cac gia tri hieu dung eiia dong dien xoay ehieu.
''
A. duoe xay dung dua treH tac dung nhiet evia dong dien.
B. chi duoc do bang cac arqpe ke xoay chieu.
C. bang gia trj trung binh chia cho ^ .
'

"1 "Jry) '••<•
D. bang gia tri cue dai chia cho 2.
Cau 2: Cau nao sau day dung khi noi vedong dien xoay chieu?
' '
A. Co the dijng dong dien jxoay ehieu de ma dien.
'
' " ''
B. Dien luong ehuyen qua tie't dien ciia day dan trong mot chu ki cua dong
dien bang 0.
C. Dien lugng ehuyen qua tie't dien cua day dan trong mot khoang thai gian
bat ki deu bang 0.
D. Cong sua't toa nhiet tuc thai tren mot doan mach c6 gia trj cue dai bang
cong sua't toa nhiet trung binh nhan vai 72 .

r = -I = 40Q

'"''•^ i

Cau 3: Cho hai cuon day c6 d i | n tra thuan (Li, n) va (L2, T2) mac noi tiep vao
hai diem A B . Goi U la hieu dien thehieu dung hai dau AB. Ui, U2 Ian lugt la

40 =>x = 15Q

hieu dien the hieu dung hai dau cuon day 1 va cuon day 2. Dc U = Ui + U2

AB = 30(km)

can CO dieu kien nao sau day?
P A . L i n = L2r2.

60-x
R

0 ' i t t v «)[!iiirh ifi \)

B

60-x

B. Lir2 = L2ri.

C. L1L2 = r i r i

D. Li + L2 = n + r2.

•,

o!:).

•

^

Cau 4: Cho mach dien gom dien tra thuan R, cuon cam thuan L, tu dien c6
dien dung C. Chon cau diing:

;,j;,

A. Dien ap tiie thoi giiJa hai dau L va cuong dp dong dien tuc thai trong
mach luon dat cue dai ciing mot liic.

B. Dien ap tiie thoi giQ-a hai dau C va cuong do dong dien tuc thai trong
mach luon dat cue dai cung mot luc.

'1, •

C. Dien ap tuc thai giija hai dau mach va cuong do dong dien tuc thai
trong mach luon dat cue dai cung mot luc.
• t'k

r

D. Dien ap tuc thoi giCra hai dau R va cuong dp dong dien tuc thoi trong
mach iuon dat cue dai cung mot luc.
Cau 5: Cho mach dien gom cuon day c6 do t u cam L noi tiep vol hpp kin X.
Phuong trinh cuong do dong dien qua mach va hieu dien the hai dau doan
mach la

•

i = IQCOS (Ot + —

252

( A ) ; U A B = UoCos cot — ( V ) .

3J

6J

X chua nhCrng phan t u nao?

A. R, L va C.
B. R va C.

C. R va L.
253


Bo trp

hien

thiic

V^t li r mil licit

h.cnh

VTV2,

t^p 2 - Chu Vdn Bi^n

Cty TNirn MTV o vvii Khang

Cau 6 ( D H 2008): Cho doan nicich gorn dien t r o thuan R noi tiep v o i t u dien co

doan mach k h i doan mgch

t r o cua doan mach la

A . CO L va C mSc n o i tiep.

B. chi co tu C.

C. CO R va C mac noi tiep.

D . co R va L mac noi tiep.

R2 +

1

•not

fi)'vj,^;/sdft;

coC

C. ^ R 2 + ( O ) C ) ^

"

1

B.

A . cung tan so v o i hieu dien the o hai dau doan m a c h va co pha ban dau

D. 7R^-(COC)^

m o t dien ap xoay chieu o n d i n h . D o thi ciia dien ap tuc t h o i gii>a hai dau

^, doan mach t h e o c u d n g do d o n g dien tuc t h o i trong mach c6 dang 1^
A. hinhsjn.

B. doan thang.

C. di^ong t r o n .

c a m k h a n g v a d u n g khang tuan theo bieu t h i k R = 2 Z L = 3Zc. Ket luan nao
,,;,;f,;Sau day la d u n g k h i noi ve c u a n g d o d o n g dien hieu d u n g chay qua cac
j p h a n t u t r o n g mach?

^m^mm^am

*
• 1
2
3
C a u 9: C h o n cau d u n g k h i noi ve d o n g dien xoay chieu?

XKA ••-•'ai.l. ••

C. D i e n l u g n g chuyen qua tiet dien thang cua day dan c6 d o n g dien xoay
chieu chay qua t r o n g m o t khoang thoi g i a n b a t k i deu bang 0.
p . Cong suat toa nhict t r u n g binh cua dong dien xoay chieu bien thien dieu
hoa.

B. H e so cong suat cang Ian thi cong suat hao p h i cua mach cang Ion.
C. D e tang hieu qua su' d u n g dien nang, ta phai t i m each nang cao he so
^

C a u 11: C u o n g d o d o n g dien l u o n l u o n som pha h o n hieu dien t h e o hai dau
doan mach k h i

C. doan mach co R va C va L mac noi tiep.
D . doan m a c h co L va C mac noi tiep.

" «*"'^

/. ^
~ •)

A . Zi. < Zc.

n v r i . f

q

B. Zi, = Zc.

'

pnif,

C. Zi = R.

D . Zi > Zc.

. D e dien ap hieu d u n g giira hai (Jau doan niach

A N k h o n g p h u thuoc R t h i tan so goc co bang

A . - i ^ .
2V2

B.(0iV2.

C

,t> gnr>
.

'

'

'

D.2(oi.

N/2

^
K

C a u 16 ( C D 2012): D a t dien ap u = U(icos(cot + 9 ) vao hai dau doan mach g o m
dien t r o thuan R va cuon cam thuan co d o t u cam L mac n o i tiep. H e so

B.-,

. C.

A.

D.

C a u 17 ( D H 2012): Dat dien ap u = Uocoscot vao hai d a u doan m a c h g o m dien
tro t h u a n R, cuon cam thuan co do t u cam L va tu dien co dien d u n g C mac
noi tiep. G o i i la c u o n g do d o n g dien tuc thoi trong doan mach; u i , U2 va us

D . Cong suat cua cac thiet bj dien t h u o n g phai c6 coscp > 0,85.

B. doan mach co R va C mac noi tiep.

mach dien nay l u o n CO

A . ^ .

A . H e so'cong suat cang Ion thi cong suat tieu t h u cua mach cang I o n .

;

chieu u = Uocoswt t h i d o n g dien t r o n g mach la i = Iocos(tL)t + TT/6). Doan

cong suat cua doan mach la

C a u 10: Chon cau tra l o i sai k h i noi ve y nghia cua he s o c o n g suat coscp?

A . doan mach co R va L mac noi tiep.

C S u 14: Dat vao hai dau doan mach RLC k h o n g phan nhanh m o t dien ap xoay

d u n g C. D a t (Oj = — ^ =

p . Gia t r j t r u n g b i n h cua c u o n g d o d o n g dien t r o n g m o t chu k i bang 0.

cong suat.

C. l u o n lech pha nil so v o i hieu dien t h e o hai dau doan mach.

tiep v o i cupn cam t h u a n co d o t u cam L , doan N B chi co t y 4 i e n v o i dien

. fi.),;>(

A . Co the d i i n g d o n g dien xoay chieu de ma dien.

= U iuv d = i i r i ^ ,'I j^ntv-'.! o ; '

hai doan mach A N va N B mac noi tiep. Doan A N g o m bien t'-o R mhc noi

••••

D . l K = l L = I rc-

-il )n\f« ;jri6:*

Cau 15 ( D H 2010): Dat dien ap u = U%/2 coscot vao hai dau doan mach A B g o m

BB. . 3
3 Il KK = 2 l L = I c . , 6 , , . , « r f , ; , 0 : e ,

c k.k-k

luonb^ngO.

B. cung tan so va c i m g pha v o i hieu dien the 6 hai dau doan mc.ch.
D . CO gia trj hieu d u n g t i le thuan v o i dien t r o cua mach.

D . eHp.

C a u 8: Cho doan mach xoay chieu R, L, C mac n o i tiep. Gia t r j cua dien tro,

A-IR=2IL=3IC.

j .

C a u 13 ( C D 2007): D o n g dien xoay chieu trong doan mach chi co dien t r o thuan

C a u 7: Cho mach dien xoay chieu chi c6 tu dien. Dat vao hai dau doan mach

254

Cau 12: C t f o n g d p d o n g dien l u o n l u o n tre pha hon hieu d i ? n tiie a hai dau

d i e n d u n g C. K h i d o n g dien xoay chieu c6 tan so goc bi chay qua thi to'ng

A.

Vjft

Ian l u g t la dien ap tuc thoi g i t i a hai dau dien tro, g i i i a hai dau cuon cam va
g i u a hai dau tu dien; Z la tong tro cua doan mach. H e thuc d i i n g la

A. i = uscoCfi

'

B. i = ^ .

C . i = ^-.^.b

D. i = ^ .

i
C a u 18 ( C D 2012): Dat dien ap u = U Q cos(a)t + ^) vao hai dau doan mach g o m
dien t r o .thuan R mac noi tiep v o i cupn cam thuan co d p t y cam L, c u o n g d p


B o t r g kien

thiic

V^t U LTDH

tren

kenh

VTV2.

tap

2 - Chu

Viln

Blcn

cty T/mriflft

f/ Khang

Vi^t

B. D i e n ap giua hai dau dien tro thuan sam pha 71/4 so v o i dien ap g i i i a hai

d o n g d i e n t r o n g mach la i = IQ sin(cot + • ^ ) . Biet Uo, lo va co k h o n g d o i . He

dau doan mach.
thuc d i i n g la

;)•• ,:AJ'r'.t

V;. vi'sTi:

C. C u o n g d o d o n g dien qua mach som pha 7T:/4 SO v o i d i e n ap giira hai dau

A. R = 3coL.

B. a)L = 3R.

C.R=>/3coL.

D . coL=^/3R.

doan mach.

Cau 19 ( C D 2012): Dat dien ap u = U%/2 cos27tft (trong do U khor-g d o i , f thay

D. Dien ap giua hai dau dien t r o thuan tre pha 7t/4 so v o i d i ^ n ap giira hai

doi du-oc) vao hai dau d i e n t r a thuan. K h i f = fi t h i cong suat tieu t h u tren
d i e n t r o bang P. K h i f = ii v o i h = 2 f i t h i cong suat tieu t h u tren d i e n t r o bang
A. V 2 P .

B. - .

CP.

dau doan mach.
Cau 24: Dat m o t dien ap xoay chieu vao hai dau doan mach g o m d i e n tro
thuan R, cuon cam thuan c6 cam khang Zi. va t u d i e n c6 d u n g k h a n g Zc

D.2P.
ll

mac nol tiep theo t h u t u tren. N e u R2 == Z i . Z c t h i

Cau 20 ( C D 2012): Dat dien ap xoay chieu vao hai dau d o a n mach X mac no!

K

A . cong suat cua mach se giam neu thay d o i d u n g k h a n g Zc.

tiep chiia hai t r o n g ba phan t u : dien t r o thuan, cuon cam t h u a n va tu dien.

H

B. dien ap giira hai dau doan mach ciang pha v o i d o n g d i e n t r o n g mach.

2

Biet r^ng d i e n ap giira hai dau doan mach X l u o n s o m pha so v o i c u o n g do
d o n g d i e n t r o n g mach m o t goc nho h o n ^ . D o a n m a c h X chua
A. cuon cam t h u a n va tu d i e n v o i cam k h a n g Ion h o n d u n g k h a n g .
B. d i e n t r a t h u a n va tu dien.
C. cuon cam t h u a n va t u dien v o i cam khang nho h o n d u n g k h a n g .
D. d i e n t r o t h u a n va cuon cam t h u a n .

'

C. d i e n ap tren doan mach RL som pha h o n dien ap tren d o a n mach RC la
71

2 •

D. dien ap tren doan mach RL cham pha hon dien ap tren doan mach RC la
_^
4'

: ice

uftft'OBn -ysidj ettl .Vfmm

HKO'O

^ n o i i iv.)\Xf •^•non oh fyitiu-j

Cau 25: D i e n ap g i u a hai dau m o t doan mach RLC noi tiep s o m pha 7T/4 SO v o i

Cau 21 ( C D 2009): Dat dien ap u = UQ cos(cot + J )

vao hai dau doan mach chi

c u o n g do d o n g d i e n . Phat bieu nao sau day la diing d o i v 6 i d o a n mach

CO tu d i e n t h i c u o n g d o d o n g d i e n t r o n g mach la i = I(icos(ft)t + cpi). Gia t r i ciia

nay?

(pi b a n g

A. H i e u so'giua cam khang va d u n g khang bang dien t r o t h u a n cua doan

A.-^.
2

B.

C. ^ .
2

4

D . ^ .
4

Cau 22 ( D H 2011): D a t d i e n ap u = U V 2 coscot vao hai dau m o t t u di?n t h i
c u o n g do d o n g d i e n qua no c6 gia t r i hieu d u n g la I . Tai t h o i d i e m t, d i e n ap
6 hai dau t u dien la u va c u o n g d o d o n g dien qua no la i . H e thuc lien he
g i i i a cac dai l u o n g la
,

u^

i^

U2

j2

1
4

M

u

"

i p

..^

.,,

B. T o n g t r o cua doan mach bang hai Ian dien tro thuan cua mach. .^jf-,
C. Tan so' d o n g d i e n t r o n g doan mach nho h o n gia t r i can de xay ra cong
hudng.
D. D i e n ap gi&a hai dau dien t r o thuan som pha TC/4 so v o i d i e n ap giija hai
ban tu dien.

^

u^
^2

i^
j2

0,444
Cau 23: D a t d i e n ap u = Uocoscot vao hai dau doan mach g o m d i e n t r o t h u a n R
va t u dien C mac no'i tiep. Biet dien ap giCra hai dau d i e n t r o t h u a n va dien
ap giira hai ban t u dien c6 gia trj h i ^ u d u n g bang n h a u . Phat bieu nao sau
day la sai ?
A . C u o n g d o d o n g d i e n qua mach tre pha n/4 so v o i d i e n ap g i i i a hai dau
d o a n mach.

mach. v

Cau 26: Dat d i e n ap xoay chieu u = Uucos27Tft (Uo k h o n g d o i , f thay d o i duoc)
vao hai dau doan mach chi c6 tu dien. Phat bieu nao sau day diing?
A. C u o n g do d o n g d i e n hieu d u n g trong doan mach cang Idn k h i tan so f

cang Ion.

;

>

B. D i e n ap giua hai dau doan mach som pha n/2 so v o i c u o n g do d o n g dien
trong doan mach.
C. C u o n g do d o n g dien hieu d u n g trong doan mach k h o n g d o i k h i tan so f
thay d o i .
D. D u n g khang cua tu dien cang Ion k h i tan so f cang I o n .

257


Cty Timnnrvown

Bo tiy hicn thiic V^t li L TDll tren kenh VTV2. t^p 2 - Chu VSn Bien

Khang

Vipt

Cau 27: D a t vao hai d a u doan mach chi c6 m o t phan tir m o t hieu d i e n the xoay

Cau 32: D o a n mach xoay chieu A B chi chua m o t t r o n g cac phan t u : D i e n t r a

chieu CO bieu thuc; U = UN/2COS m t - • ( V ) t h i d o n g d i e n chay qua phan
4^
V

thuan, cuon d a y hoac t u dien. K h i dat m o t dien ap u = Uocos(cot + n/6) V vao
hai d a u A B t h i d o n g dien t r o n g mach co bieu thuc i = Iocos(cot - n/3) A.

tir d o CO bieu thuc i = lV2 sin c o t - - ( A ) . Phan t u d o la m o t c

D o a n mach A B chua

A. dien t r a thuan.

B. t u dien.

C. cuon day t h u a n cam.

•.i,,,::^:.,:,,

D . cuon day c6 d i e n t r a .

C a u 28 ( D H 2010): D a t dien ap u = Uocoswt vao hai d a u cuon cam. thuan c6 do
t u cam L t h i c u o n g dt) d o n g dien qua cuon cam la
'

A . i = H o cos(o)t + - ) .

o)L

^

B. i = - H )

^ C . i = HiIcos(c,t-^).
(oL
2

^ ,
• I '

'

B. D i ^ n t r o t h u a n . "

C. C u o n d a y co d i e n t r a t h u a n .

D . C u o n d a y t h u a n cam.

"

C a u 33: D i e n ap giira hai d a u m o t doan mach R L C no'i tie'p s a m p h a ^ so vc>i
c u o n g d o d o n g dien. Ket luan nao sau day la dung?
A . T o n g i r o ciia mach bang 2 Ian dien t r o R cua mach.

cos((ot + - )

(0LV2

r

A . T u dien.

2

B. H i e u so g i u a cam k h a n g va d u n g khang bang 0.

'

C. C a m k h a n g bang V2 Ian d u n g khang.

D.i=-4^cos(cot-^).
coLV2

2

"f''-''

> 1f

"

' <

D . T o n g t r o cua mach bang V2 Ian dien t r o R cua mach.'

C a u 29 ( C D 2010): D a t dien ap xoay chieu u=U()Coso)t vao h a i d a u doan mach

C a u 34: D a t m o t d i e n ap xoay chieu co gia t r j hieu d u n g U va tan so goc ro

chi CO dien t r o t h u a n . Goi U la dien ap hieu d u n g g i i i a h a i d a u doan mach;

k h o n g d o i vao hai d a u m o t doan mach co R, L, C mac no'i tie'p, i r o n g d o R la

H i , lo va I Ian l u o t la gia t r i tuc t h o i , gia t r i cue dai va gia t r i hi?u d u n g ciia

m o t bien t r o , Zc ^ Zi. K h i thay d o i R de cong sua't cua doan mach cue dai

:

c u o n g d o d o n g d i e n t r o n g doan mach. H e thuc nao sau day sai?

thi

A . — - -1- = 0 .
Uo
lo

A . cong sua't cue d a i d o bang

B.

Uo

+ ^ = N/2 . C. ^ - T = 0 .
I„
U I

D. ~ + ^ = 1 .
Uo

C a u 30 ( C D 2010): D a t dien ap u = Uocoswt co (o thay d o i d u o c vao h a i dau
doan mach g o m cuon cam thuan c6 do t u cam L , dien t r o t h u a n R va tu
dien CO d i e n d u n g C mac n o ! tie'p. K h i co <

J— t h i
VLC

,,,
'" '

A. dien ap hieu d u n g g i u a hai d a u dien t r a thuan R bang d i e n ap hieu d u n g
g i u a hai d a u doan mach.
d u n g g i u a h a i d a u doan mach.
doan mach.
D . c u o n g d o d o n g dien t r o n g doan mach cung pha v o i d i ^ n ap g i i i a h a i dau
^

C a u 31(CD 2008): D a t m o t hieu dien t h e x o a y chieu co gia t r i hieu d u n g k h o n g
d o i vao hai d a u doan mach R L C k h o n g phan nhanh. H i e u d i e n the g i i i a hai
dau
:

A . doan mach l u o n cung pha v a i d o n g dien trong mach.
B. cuon day l u o n ngugc pha v o l hieu dien the'giua hai d a u t u dien.
C . cuon d a y l u o n v u o n g pha v a i hieu dien the'giua hai d a u t u dien.
D . t u d i e n l u o n c u n g p h a v o i d o n g dien t r o n g mach.

258

- *•

C. t o n g t r a ciia doan mach la 2 | Z L - Z c | .

'

<

D . he so'cong sua't ciia doan mach la coscp = — .
C a u 35 ( C D 2007): D o a n mach dien xoay chieu g o m dien trtV thuan R, cuon day
l i n g la h i ^ u d i e n the tuc t h o i 0 hai dau cac p h a n t u R, L va C . Q u a n he ve
pha ciia cac hieu dien the'nay la

C . c u o n g d o d o n g dien t r o n g doan mach tre pha so v a i d i e n ap giua hai dau

doan mach.

B. gia t r j bien t r o la ( Z L + Z , ; ) .

thuan cam (cam thuan) L va tu dien C mac no'i tie'p. K i hieu UK, UI., UC t u o n g

B. dien ap hieu d u n g gii>a hai d a u dien t r o t h u a n R n h o h a n d i e n ap hieu

i

.

A.

UR tre pha 7T/2 so vcS-i uc.

C. UL s o m pha TI/2 SO v a i uc.

'

1 ,<

.

B. uc tre p h a TT so v a i UL. '
D . Uu s o m p h a n/2 so v o i ui,.

C a u 36 ( C D 2007): D a t vao hai d a u doan mach R L C k h o n g p h a n n h a n h m o t
hieu d i e n t h e x o a y chieu u=Uo sincot. K i hieu U u , U L , Uc t u a n g u n g la hieu
dien the hieu d u n g 6 h a i d a u dien t r a thuan R, cuon day t h u a n cam (cam
thuan) L va t u dien C. Ne'u U R = Ui./2 = Uc t h i d o n g d i e n qua d o a n mach
A . tre p h a n/2 so v o i hieu dien the'a hai d a u doan mach.

* ' '

B. tre p h a n/i so v a i hieu dien the 6 h a i dau doan mach.

'*

C. s o m pha n/4 so v a i hi§u dien the'a hai dau doan mach.
D . s a m pha Tr/2 so v o i hieu dien the'6 hai dau doan mach.
259


Bo trg hidn thitc

V4it IILTDH

tr&n kenb

VTV2. t^p 2 - Chu VSn

Blen

Cau 37 (CD 2009): Dat mot hieu dien the xoay chieu c6 tan so thay doi dugc

Cau
42: Khi dien ap giiia hai dau doan mach RLC mac no'i tie'p cham pha 7t/4 so
(
voi dong dien trong mach thi

vao hai dau doan mach R L C khong phan nhanh. Khi tan so'dong dien troni>

A. tan so cua dong dien trong mach Ion hon gia tri can xay ra hien tugng

mach Ion hon gia tri 1/(2rt V L C )) thi
A. hieu dien the hieu dung giira hai dau dien tro bang hieu dien the hieu
,^^,4..,^^ „;;;K A , ,.,M.

dung giua hai dau doan mach.

- ^ .

cgnghuong.
is;.
B. tong tro cua mach bang hai Ian thanh phan dien tro thuan R cua mach.
C. hieu so giira dung khang va cam khang bang dien tra thuan ciia mach.
D. dien ap giiia hai dau dien tro sam pha 7:/4 so vai dien ap giiia hai dau tu

B. hieu dien the hieu dung giiia hai dau cuon day nho hon hieu dien the
hieu dung giiia hai ban tudien.
C. dong dien chay trong doan mach cham pha so v6i hieu dien the'giiJa hai
dau doan mach.
dung giija hai dau doan mach.
Cau 38: D61 voi mot doan mach xoay chieu R, L, C mac no'i tie'p, biet rang dien
tro thuan R ?i 0, cam khang Zi ^ 0, dung khang Zc ^ 0, phat bieu nao sau day
diing? Tong tro cua doan mach
A. kion bang tong Z = R + Zi. + Zc.
'> 1.

khong the nho hon cam khang ZL.

C. khong the nho hon dung khang Zc. n<;
D. khong the nho hon dien tro thuan R.

n ' ['fji

;
V

Cau 39: Ggi u, i Ian higt la dien ap tuc thai giCra hai dau doan mach va cuong
do dong dien tuc thoi trong mach. Lua chgn phuong an dung:
A. Doi vai mach chi c6 dien tro thuan thi i = u/R.
B. Doi vai mach chi c6 tu dien thi i = u/Zc.
C.

Doi voi mach chi c6 cuon cam thi i = U/ZL.

D. Doi voi doan mach noi tie'p u/i = khong doi.

i*,•.•,•1

,

hai dau doan mach xoay chieu va cuong do dong dien trong mach nguoi ta

'

HTV,,.

,

, ,

dien do c6 the la
A. chi dien tra thuan.
rhun j:m^il ir^^h 'urr.
B. chi cuon cam thuan.
1 : ;
;
„;;t, 4 .
C. chi tu dien.
^
^ ,„.^j.^
^^^.^.^j^',. 1^;,
_
D. tu diei. ghep noi tie'p voi dien tro thuan.
Cau 44: Ket luan nao sau day dung khi so sanh tan so fi cua dong dien xoay
chieu trong mot doan mach va tan so h cua dien ap dat tren hai dau doan

mach d o ?
A. fi = 3f2.
B. fi = 4f2. , ,. ! C. fi = k.
D. fi = 2f2.
Cau 45: Ket luan nao sau day la dung khi so sanh chu ki bien doi Ti cua cong
sua't toa nhiet tuc thai cua dong dien xoay chieu vai chu ki biC'n doi T2 cua
dong dien do?
A.Ti
J> t ' ^ ? ! ' "
w

B.T1-T2.

C.T2 = 2Ti.

Ti = 3T2.

Cau 46: Ket luan nao sau day la dung trong truang hop co.L >
,.

,.

cua mach
co.C

Cau 40: Hay chgn cau phat bieu sai.

dien xoay chieu RLC mac no'i tie'p

A. Nguyen tac tao ra dong dien xoay chieu dua tren hien tugng cam ling
B.

tv-*-—)•

nhan thay, do thj dien ap va do thj dong dien deu di qua goc tga do. Mach

D. hieu dien thehieu dung giua hai dau dien tra Ian han hieu di^n thehieu

B.

dien.

Cau 43: Khi nghien cuu dong thai do thi phu thugc thai gian cua dien ap giCia

A. trong mach CO cgng huang dien.
B. he

Khi do cuong do va hieu dien the cua dong xoay chieu nguoi ta dung

C. Hieu dien thegiiJa hai dau di?n tra thuan R dat gia tri cue dai.

ampe ke va von ke c6 khung quay.

D. Cuang do dong dien cham pha hon hieu dien the giiJa hai dau doan mach

C. So chi ciia ampe ke'xoay chieu cho biet gia tri hieu dung c i a cuong do

* '''

Cau 47: Mot mach dien khong phan nhanh RLC dugc mac v a o mot hieu dien
the xoay chieu u = U()Cos(a)t) voi Uo khong doi nhung co thay do- dugc. Cong

dong dien xoay chieu.
D. So' chi cua von ke xoay chieu cho biet gia trj hieu dung ciia hieu dien the
xoay chieu.

C0S9

> 1.

i'

dien tu.

CO

cong sua't

^-

, ^

^

,

Cau 41: Hai cuon thuan cam L i va L2 mac noi tie'p trong mot mach dien xoay
chieu CO cam khang la
Iff> ) •.

sua't tieu thu ciia mach dien se c6 cung gia tri la P nao do ne'u tan so' goc ©
bang coi hoac C02. Ta c6 quan he
1
A.

COl + C O 9 =

r—-

VLC

C. ©1.(02 = — .

A. Z L = ( L , - L 2 ) a ) .

B. Z L = ( L , + L2)(o.

C. Z L = ( L i - L 2 ) / f f l .

D. Z L = ( L , + L 2 ) / c o

.

,

„
B.

2

(Ol + © 2 =

r — •

yj,
•

• •

N/LC

D. duy nhat khi ©1 = ©2.

.,

261


so tir cam L, dien t r o thuan R va m o t tu dien C c6 dien d u n g thay d o i duoc.

./ B.
B som pha hon c u o n g do d o n g dien la TC/6.
C. tre pha hon c u o n g do dong dien la n/4.

Dat vao hai dau mach m o t hieu dien the xoay chieu xac d i n h u = Uocos(cot)

D . tre pha h o n c u o n g do dong dien la 7t/6.

l a u 48: M o t mach dien xoay chieu i

(vdi Uo va CO k h o n g doi). Ket luan nao sau day la sai ve hien t u g n g t h u d u o c

--^x

Cau 52: M o t mach dien xoay chieu RLC mac noi tiep theo d i i n g t h u t u gom

k h i thay d o i C?

cuon cam thuan co cam khang Zi,, bien t r o R va t u dien c6 d u n g khang Z c .

A. Deh gia trj ma hieu dien the hieu d u n g tren tu dien dat gia t/j cue dai thi

Ne'u dien ap hieu d u n g tren doan RC k h o n g thay d o i k h i chi R thay d o i t h i

mach dien c6 t i n h d u n g khang.

A . Z L = 2ZC.

B. Gia t r i cue dai ciia hieu dien the'hieu d u n g tren tu C dat d u o c nho hon

B. Z C =

2ZI.

C . ZI = 3ZC.

D. ZL = ZC.

Cau 53: M a c h dien xoay chieu noi tiep A B g o m dien t r o thuan 1^, cuon cam

hoac bang gia t r j hieu d u n g cua hieu dien the tren hai dau mach dien.

thuan L va tu d i e n C (R, L , C khac 0 va h u u han). 6 t h o i d i e m t dien ap tuc

C. K h i xay ra cong h u o n g thi hieu dien the'tren tu dien se v u o n g pha so v o i

thoi giua hai dau doan mach A B va dien ap tiic thoi tren L m o i dat den nua

hieu d i e n the tren hai dau mach dien.

gia trj bien do t u o n g u n g . Dien ap giua hai dau doan mach

D . V o i gia trj cua C l a m cho cong sua't tieu thu tren cuon day dat cue dai thi
'

^^'^

A . som pha hon c u o n g do d o n g dien la 7r/4.

d o n g dien t r o n g mach se ciing pha so v o i hieu dien the Iren hai dau

B. som pha hon c u o n g do d o n g dien la n/6.

mach dien.

C. tre pha h o n c u o n g do d o n g dien la n/4.

Zau 49: M o t doan mach g o m dien tro R mac no'i tiep v o i cuon day. Biet dien ap
giOa hai dau dien t r o va hai dau cuon day Ian l u g t la

'V'
''

'

D . tre pha h o n c u o n g do d o n g dien la n/6.

= 120cos(1007tt) V

Cau 54 ( C D 2008): M o t doan mach g o m tu dien co dien d u n g C , dlen t r o thuan

^^
v a u j - 1 2 0 c o s 100nt + — V. Ket luan nao d u o i day k h o n g diing?

R, cuon day co dien t r o trong r va he so' t u cam L mac noi tiep. K h i dat vao

A . C u o n day CO dien t r o r khac 0.

mach CO gia t r j hieu d u n g la I . Biet cam khang va d u n g khang t r o n g mach la

f

hai dau doan mach hieu dien the u = UV2sin(i)t (V) thi d o n g dien trong
khac nhau. C o n g sua't tieu t h u trong doan mach nay la

B. D i e n ap giira hai d a u doan mach tre pha — so v o l d i ^ n ap g i u a hai dau
6
cuon day.
C. D i e n ap h i ^ u d u n g giija hai dau doan mach la 60\/3V.

A . U V ( R + r).

B. (r + R ) P .

C. PR.

D . UI.

Cau 55: M o t dien t r o thuan R mac vao mach dien xoay chieu tan so 50Hz.
M u o n d o n g dien t r o n g mach som pha hon hieu dien the giua hai d a u doan

s u f ;

mach m o t goc

D . H e so'cong sua't cua doan mach bang

n g u o i ta phai

A . mac them vao mach m o t tu dien noi tiep v o i dien t r o .
Zau 50: M a c h dien A B la hai mach dien xoay chieu g o m 3 phan t u L - R - C

mac

C. thay dien t r o noi tren bang m o t tu dien.

R noi giua hai d i e m M - N , tu dien C n o i g i i i a hai d i e m N va B. Ket l u a n nao

D . thay d i e n t r o noi tren bang m o t cuon cam.

A . UAM s<'>m pha h o n so v o i UAN.

)
,{, , ' j i l

' ^

B. mac t h e m vao mach m o t cuon cam noi tiep v o i dien t r o .

n o i tiep theo t h u t u do. C u o n cam thuan L noi giira hai d i e m A - M , d i ^ n t r o
sau day la khong dung?

•

'

Cau 56: M a c h d i ^ n xoay chieu RLC noi tiep tan so goc thoa m a n co^LC 5^ L H$

fl

so'cong sua't cua mach dang bang 0,5 72,

B. UAN sam pha h o n so v o i UAH.

ne'u tang R t h i

A . tong t r o cua mach giam.

C. UAN v u o n g pha so v o i u\w k h i mach cong h u o n g .

B. cong sua't toan mach tang.

D . UMN som pha so v o i UND.

C. h# so cong sua't cua mach g i a m .

rau 51: M a c h dien xoay chieu noi tiep A B g o m dien t r o t h u a n R, cuon cam

*
'

'
'

D . hieu d i e n the'hi^u d u n g a hai dau dien tro R tang.

thuan L va tu dien C (R, L, C khac 0 va hOu han). 6 t h o i d i e m t dien ap tiic

Cau 57: M o t mach d i ^ n xoay chieu g o m cuon cam thuan co cam k h a n g Zi., bien

thoi gill a Iiai dau doan mach A B va dien ap tuc t h o i tren C m o i dat den nua

t r o R va t u di?n co d u n g khang Zc mac noi tie'p theo t h u t y L , R, C. K h i chi

gia trj bien do t u o n g u n g . D i e n ap hai dau doan mach
A . som pha h o n c u o n g do d o n g dien la n/A.

fljl R thay
H|

H

d o i ma Z L =

2Zc

dien ap hieu d u n g tren doan mach chua RC

A . k h o n g thay d o i .
^

263


B. l u o n n h o h o n dien ap hieu d u n g hai dau doan mach.

Cau 63: Phat bieu nao sau day d u n g v o i cuon thuan cam?

C. l u o n g i a m .

A . C u o n cam c6 tac d u n g can t r o d o i v o i d o n g dien xoay chieu, k h o n g c6

D . CO liic tang c6 liic g i a m .

tac d u n g can t r o d o i v o i d o n g dien mot chieu (ke ca d o n g dien m o t chieu

C a u 58: M o t d i e n t r o thuan R mac vao mach dien xoay chieu tan so' 50 H z
Muo'n d o n g d i e n t r o n g mach som pha h o n d i e n ap giua hai dau doan mach
• m o t goc 71/2, n g u o i ta phai
A . mac t h e m vao mach m o t tu dien noi tiep v 6 i dien tro.

•

i j , B. mac t h e m vao mach m o t cuon cam thuan noi tiep v o i d i e n t r o .
C. thay d i e n t r o n o i tren bang m o t tu dien.

s y f l t,;i,

•

chieu.

<

D . Cam k h a n g ciia cuon cam khong p h u thuoc tan so cua d o n g d i e n xoay

, n;

chieu.

C a u 59 ( D H 2008): N e u t r o n g m o t doan mach dien xoay chieu k h o n g phan
n h a n h , cu-ong d o d o n g d i e n tre pha so v o i hieu dien t h e g i O a hai dau doan
A . t u dien va bieh tro.

ji;
;v

nyih

OI)

cam CO cam k h a n g Z L , tu dien c6 d u n g khang Zc mac noi tiep t h i tong tro
cua doan mach

A . H e so'cong suat ciia doan mach bang khong.

nho.
Cau 65: T r o n g m o t doan mach dien xoay chieu R, L, C mac n o i tiep, phat bieu
nao sau day d i i n g ?
d u n g tren d i e n t r o thuan R.

B. k h o n g the n h o h o n cam khang Z i .

*•'

x . >'. • •

»

B. D i e n ap hieu d u n g g i i i a hai dau doan mach c6 the n h o h o n d i e n ap hieu

A..,,

D . khongj the nho h o n d u n g khang Zc.

d u n g tren bat k y phan t u nao.

' '

Cau 61: O hai dau m o t dien t r o R c6 dat m o t hieu dien the xoay chieu U A C mot

hieu dien the k h o n g d o i U D C . De d o n g dien xoay chieu c6 the qua d i e n tro

C. D i e n ap hieu d u n g giira hai dau doan mach l u o n Ion h o n dien ap hieu
d u n g tren m o i p h a n t u .
D . C u o n g do d o n g dien chay t r o n g mach l u o n lech pha v o i hieu dien the

va chan k h o n g cho d o n g dien k h o n g d o i qua no ta phai;

giua hai dau doan mach

A . Mac song song v o i dien tro mot tu dien
B. Mac no'i tiep v o i dien t r o m o t t i l dien C.

Cau 66: T r o n g mach dien xoay chieu, so'chi cua v o n k e c h o bie't gia t r j nao cua

C. Mac song song v o i dien tro m o t cuon thuan cam L .

3.

D . Mac no'i liep v o i d i f n t r o m o t cuon thuan cam L .

hieu dien the? M o t v o n ke m§c vao hai dau t u dien t r o n g doan mach xoay
chieu, chi so ciia v o n ke la U . K h i do thuc su tu d i e n p h a i chju m o t hieu

Cau 62: Phat bieu nao sau day la k h o n g dung?

dien the'toi da la bao nhieu?

A . D i e n ap bien d o i dieu hoa theo thoi gian goi la dien ap xoay chieu.
.

C. D o n g dien c6 cuong do bieh d o i t u a n hoan theo t h o i gian goi la dong dien
xoay chieu.

i^y,

. D . D o i v o i d o n g d i e n xoay chieu, di$n l u g n g chuyen qua m o t tiet dien
,.

^

.

^

A . V o n k e c h o bie't gia t r j tuc thoi. H i e u d i e n the'toi da m a tu d i e n p h a i chiu

B. Sua't dien d o n g bieh d o i dieu hoa theo thoi gian goi la suat d i e n d o n g

264

CO t u dien?

A . D i e n ap hieu d u n g gii>a hai dau doan mach k h o n g n h o h o n dien ap hieu

A . k h o n g the nho h o n dien t r o thuan R.

thang day dan t r o n g m o t chu k i bang 0.

Cau 64: Phat bieu nao sau day la sai k h i noi ve docin mach dien xoay chieu chi

C. C o n g sua't tieu t h u cua doan mach la khac k h o n g .

C a u 60: N e u m a c h d i e n xoay chieu c6 d u 3 phan tir: d i e n t r o R , cuon day thuan

:t /•

asoij.'p.(n,''ii

D . Tan so goc cua d o n g dien cang Ion thi d u n g khang cua doan mach cang

D . dien t r o thuan va cuon cam.

•';

&ii^f^:H.qK}(iP!S({'i

d o a n mach.

C. d i e n t r o t h u a n va tu dien.

xoay chieu.

Jiii-Dfil^^t^i'' whS^fSiOfn

B. D i e n ap giCra hai ban tu dien tre pha 7i/2 so v o i c u o n g d o d o n g dien qua

mm r.nq S , :

B. cuon day t h u a n cam va tu dien v o i cam k h a n g nho h o n d u n g khang.

_ , , C . l u 6 n bang t o n g Z = R + Zi. + Z c .

B. C u o n g d o d o n g d i e n hieu d u n g qua cuon cam ti le v o i tan so d o n g dien.
C. Cam k h a n g cua cuon cam ti le nghich v o i chu k i ciia dorig d i e n xoay

,

D . thay dien t r o noi tren bang m o t cuon cam t h u a n .

mach, t h i doan mach nay g o m

CO c u o n g d o thay d o i hay d o n g dien k h o n g doi).

,.

laUV2.

B. V o n k e c h o biet gia trj hieu d u n g . H i e u dien the'toi da ma tu d i e n phai
chiu l a U / V 2 .
C. V o n ke cho bie't gia t r i hieu d u n g . H i e u dien the toi da m a tu d i e n phai
chiulaU^/2.

'

.

, , • V
265

D. V o n ke'cho bie't gia tri bien do. H i e u dien the to'i da ma tu dien phai chiu
laU.
Cau 67: T r o n g mach R L C mac no'i tiep, do lech pha ciia d o n g dien so v o i dien

Qi\X 72: T r o n g t r u o n g h o p nao t h i k h i tang dan dien d u n g C ciia tu dien t r o n g

ap giua hai dau doan mach p h u thuoc vao

toan mach R , L , C mac no'i tiep, cuong do d o n g dien hieu d u n g tang roi iai

A . c u o n g d o d o n g dien hieu d u n g trong mach.
{

C. hieu dien the'tren ca ba phan t u R , L, C deu bang 0.
p . hieu dien the'tren dien tro R va tren t u dien C bang 0 con tren cuon cam
LkhacO.
••-iA.-',.^
'-ui^'^^i^
i

B. dien ap hieu d u n g giiTra hai dau doan mach.

'

C. dac t i n h cua mach dien va tan so'dong xoay chieu.

ir^r^vir

D . each chon goc t h o i gian de tinh pha ban dau.

'

=Zc

A.

ZL

C

Z L < Z C


:

,

B. Z L
^ ^

>Zc

'

V'

D. Z L = Z C = R

•

'

Cau 68: T r o n g doan mach xoay chieu g o m dien t r o thuan, t u dien noi tiep v o i

Cau 73: T r o n g mach xoay chieu g o m R , L , C mac no'i tiep. D o lech pha giua

i f ; cuon day, d i e n ap tvic thoi giua hai dau dien tro thuan R va g i i i a hai dau

hieu dien t h e g i O a hai dau toan mach va c u o n g do d o n g dien t r o n g mach la

cuon day c6 cac hieu thtVc Ian l u g t la U K = UoRCoso)t (V) va UA •= Uodcos(a)t +
7t/2) ( V ) . Ket l u a n nao sau day la sai?
(il A . Dien ap giiia hai dau cuon day nguoc pha v o i d i ^ n ap giiia hai ban ciia tu
dien.

-^i (

'•

B. C u p n day CO dien tro thuan.

\

C. C u o n day la t h u a n cam.

•'•f"

:

\'f

* .•<-v.i»

3
A . mach dien c6 t i n h d u n g khang.

B . mach dien c6 t i n h cam khang.

C. mach d i e n c6 ti'nh t r o khang.

D . mach cong h u o n g dien.

Cau 74: T r o n g cac d u n g cu tieu t h u dien n h u quat, t i i lanh, d o n g co...ngu6i ta
.,:„,,j:^

.j,;

D . C o n g sua't tieu t h u tren mach khac 0.
C a u 69: T r o n g m o t doan mach c6 cac phan tir R, L, C mac no'i tiep. Phat bieu
nao sau day la dung?
,

(p = cPu -cpi = — , dieu nay c h u n g to'

A . C u o n g d o h i ^ u d u n g qua cac phan t u R, L, C l u o n bang nhau, n h u n g
c u o n g do tuc t h o i chua chac da bang nhau.
B. H i e u dien the h i ^ u d u n g giira 2 dau doan mach l u o n bang t o n g h i § u dien
the'hieu d u n g tren t u n g phan t u .

C . H i e u dien the tuc thoi g i i i a 2 dau doan mach l u o n bang t o n g hieu dien
the tuc t h o i tren t u n g phan t u .
D . C u o n g do d o n g dien va hieu dien the tiic t h o i l u o n khac pha nhau

C a u 70: T r o n g m o t doan mach d i ^ n xoay chieu RLC mac n o i tiep, cong sua't

phai nang cao he so'cong sua't n h a m
A . tang cong sua't tieu thu.

'

B . giam cong sua't tieu t h u .

'

>> ' *
'

C. thay d o i tan so ciia d o n g dien.
D. tang hieu sua't ciia viec su d u n g dien.

'

Cau 75 ( D H 2007): T r o n g m o t doan mach dien xoay chieu chi c6 t u dien t h i
hi§u dien the'd hai dau doan mach

I

!> n

A . som pha n/2 so v o i cuong do d o n g dien.
B . som pha Ti/4 so v o i cuong do dong dien.
C. tre pha n/2 so v o i c u o n g do d o n g dien.

^^^^^^^^^
i

^

i i i . ?, i ,
' '

'

\

D. tre pha n/A so v o i c u o n g do d o n g d i ^ n .
Cau 76 ( D H 2007): T r o n g m o t doan mach dien xoay chieu k h o n g phan nhanh,

tieu thu tren ca doan mach

cuong do d o n g dien som pha c\) ( v o i 0 < c|) < 0,57i) so v o i hieu d i e n the a hai

A . chi p h u thuoc vao gia trj dien t r o thuan R ciia doan mach.

dau doan mach. Doan mach do

' B. l u o n bang t o n g cong sua't tieu t h u tren cac dien t r a thuan.

A . g o m d i e n t r o thuan va tu dien.

Q. k h o n g p h u thuoc g i vao L va C.

B . chi CO cuon cam.

D . k h o n g thay d o i neu ta mac them vao doan mach m o t t u d«en hoac mot

C. g o m cuon t h u a n cam (cam thuan) va tu dien.

cuon day thuan cam.
Cau 71: T r o n g mach xoay chieu R L C mac noi tiep (cuon day L t h u a n cam), vao
t h o i d i e m c u o n g d o d o n g dien t r o n g mach bang 0 t h i
A . hieu d i e n the'tren dien t r o R bang 0 con tren hai phan t u con lai khac 0.
B. hieu dien the'tren dien t r o R va tren cuon cam L bang 0, con tren t u dien C
thi khac 0.
266

D. g o m d i e n t r o thuan va cuon thuan cam (cam thuan).
Cau 77 ( C D 2009): T r o n g doan mach dien xoay chieu g o m d i e n tre thuan, cuon
cam t h u a n va t u d i e n mac noi tiep t h i
1^. dien ap giua hai dau tu dien nguoc pha v o i dien ap g i u a hai dau doan
mach.
B. d i ^ n ap g i i i a hai dau cuon cam cung pha v o i d i ^ n ap g i u a hai d a u t y dien.
267


C t y TNHH

C. dien ap giij-a hai dau t u dien tre pha so v o i dien ap giua hai dau doan
mach.

D . dien ap giira hai dau cuon cam tre pha so v o i dien ap giua hai dau dogn
;!vAVr>:

mach.

B.

A.

C =

C

C = (R + R i f - 4 7 r 2 f V •

noi tiep v o i cuon cam thuan, so v o i dien ap giiia hai dau doan mach thi
c u o n g do d o n g dien t r o n g mach c6 the
A . tre pha - .
^ 2

B. som pha - .
4

C. som pha - .
2

D . tre pha - .
4

C a u 79: T r o n g mach dien g o m 2 cuon day Ri, L i va R2, L2 mac noi tiep nhau

vao m o t n g u o n c6 gia t r j hieu d u n g la U . Goi U i , U2 la hieu c'ien the hieu
d u n g tren hai cuon day. D i e u kien de U = U i + U2 la
A . L i L 2 = RiR2.

B.

U

L2

R,

R2

Vift

C = -

R + R j +27tfL •

(R + R i f + 4 7 i 2 f 2 L 2

...,jf;, r<'V!fo^»:ii*%:S:;r«;.J,,5ri.>l i d t . c

C a u 78 ( C D 2009): T r o n g doan mach d i e n xoay chieu gom dien t r o thuan mac

MTV u V VII K h a n g

D. C =

L
R + R i -2TtfL

Cau 84(DH 2008): Cho doan mach dien xoay chieu g o m cuon day co dien trcx
thuan R, mac noi tiep v o i t u dien. Biet hieu dien the g i i i a hai dau cuon day
lech pha ^ so v o i hieu dien the giCra hai dau doan mach. Mo'i lien he gii>a
dien t r o t h u a n R v o i cam k h a n g Zi. cua cuon day va d u n g k h a n g Zc ciia tu
dien la

r!'»Rfn

r.f'n n i f n-'ilS «>nf.}-.< j

A . R2 = Zc(Zi - Zc).

B. R2 = Zc(Zc - Z L ) .

C. R2 = Z L ( Z C - Zi.).

D . R2 = Zi (Zi -

Zc).

Cau 85: Cho d o n g dien xoay chieu chay qua m o t tu dien. K h i d o n g dien tuc
C. ^

=

R2

D.

Li +

L2= Ri + R2

thoi dat gia trj cue dai thi dien ap tuc thoi b hai dau tu dien co gia t r i bang

Ri

Cau 80: Cho mach dien xoay chieu RLC mac noi tiep, t r o n g d o c6 t u dien C
thay d o i duoc. Dat vao hai dau doan mach tren m o t hieu dien the xoay
chieu CO bieu thiic u = U>/2coso)t. K h i thay d o i dien d u n g cua t u dien de
hieu d i e n the hieu d u n g giOa hai ban t u dien dat gia t n cue dai va bang 2U.
Q u a n he giua Zi va R la
A.

,,r H O ) r

B. Z L = 2 R .

Z L = ^ .

C. Z L = R N / 3 .

D.

ZL=3R.

Cau 81: Cho mach R, L, C tan s o c i i a m a c h c6 the thay d o i duoc, k . i i co = (Og thl

cong suat tieu t h u t r o n g mach dat gia t r j cue dai, khi co = coj hoac co = CO2 thi
mach CO cirng m o t gia t r j cong suat. M o i lien he giiia cac gia t r i ciia co la
A
A.

2

2

2

r,

CO,) = CO1 + 0)2 .

B . coy =

C. COQ = CO1.CO2.

•

I W1CO2
— ' — ^

v)

cho Ukm.ix, Ui.ni.ix, U c i i i . i v . Ta CO

to

= f .

B. f o = f , + f 2 .

,.
C. f „ = f .

t2

t2

tj

tiep; u ^ B = U Q s i n 2 n f t . Co d j n h Uo, f, R, Ri, L , thay d o i C. T i m quan he ^
v o i f, R, Ri, L de h i ^ u d i ^ n the hi§u d y n g cua ty C d^t gia t r j c\fc dai
* *

D. 0.

Cau 86: Cho doan m a n h dien xoay chieu g o m cuon day co dien t r o thuan r, d o
t u cam L mac no'i tiep v o i t u dien co dien d u n g C. Biet hieu dien the giiia
hai dau doan mach c i i n g pha v o i c u o n g d o d o n g dien, phat bieu nao sau
day la

sai:

A . H i e u dien the hieu d u n g tren hai dau cuon day Ion h o n hieu d i ^ n the
hieu d u n g tren hai dau doan mach

r f j . - m n»

s rnei-} "J

B. T r o n g mach dien xay ra hien t u o n g cong h u o n g dien
C. Cam k h a n g va d u n g khang cua doan mach bang nhau

i ; ' i/'

D. H i e u d i e n the tren hai dau doan mach v u o n g pha v o i hieu dien the tren
hai dau cuon day

cua C de mach xay ra hien t u o n g cong h u o n g (hoac cong suat, d o n g dien
1

trong mach dat gia tri cue dai) la: ^ = ^
.C,

C2y

B. Thay d o i L thay ton tai hai gia trj L i , L2 mach co cijng cong suat. Gia tri

D.

Cau 83: Cho mach dien xoay chieu A B gcim R, cuon day (L, Ri), l u C mac noi

268

B. cue d a i .

A . Thay d o i C thay ton tai hai gia trj C i , C2 mach co cung cong suat. Gia t r j

D . (OQ = C0| + CO2 .

thay d o i duoc. Goi fo, fi, h Ian l u o t la cac gia trj cua tan so' d o n g dien lam

A. f

nua gia t r j cue dai.

Cau 87: C h o n cau sai: Cho doan mach RLC noi tiep:

.

Cau 82: Cho mach dien xoay chieu k h o n g phan nhanh RLC co tan so d o n g dit'n

'

A.

C. mot phan t u gia t r i cue d a i .

cua L de mach xay ra cc)ng h u o n g (hoac ccing sua't, d o n g dien trong
mach dat gia t r i cue dai) la: L = i ( L | + L 2 ) .

" ' '

C. Thay d o i co sao cho k h i co = co, hoac co = CO2 thi mach co ciang cong suat.
Cong suat t r o n g mach dat gia trj cue dai k h i co =

^coiC02 . ' •

269


Bo

trf) hicn

thitc

V^t li LTDtl

tren

k&nh

V T V 2 . t^p

< Ini VSn

'

Cty

Blen

Train

MTV

DVVH

Khang

Vi^t

C. t r o n g mach CO cong h u o n g dien.

D. Thay d o i R thay k h i R = R i hoac R = R2 t h i mach tieu t h u cong suat ban

D. dien ap giua hai d a u cuon cam lech pha 7T/6 SO v o i dien ap j i u a hai d a u

n h a u . M a c h tieu t h u cong suat cue dai k h i R = •j(R^ + R2 ) .

doan mach.

Cau 88: D o n g dien (xoay chieu) tuc thoi t r o n g mot doan mach R L C mac n^^j

Cau 93 ( D H 2007): Dat hieu dien the'u = Uosincot (Uo k h o n g doi) vao hai dau

tiep d a n g som pha h a n so v o i dien ap tuc thoi giua hai dau dean mach. Ta

doan mach RLC k h o n g phan n h a n h . Bie't dien tro t h u a n ciia mach k h o n g

l a m thay d o i t r o n g cac thong so ciia doan mach bang each neu sau day

doi. K h i CO hien t u o n g cong h u o n g dien t r o n g doan mach, phat bieu nao

M u o n xay ra hien t u o n g cong h u o n g dien t r o n g mach, ta phai

sau day sai?

A . tang tan so d o n g dien xoay chieu.
1

B. g i a m dien d u n g cua tu dien.
*

D. tang dien t r o cua mach.

>

.

tiic t h a i o hai dau dien tro R.

!

C. Cam k h a n g va d u n g khang cua doan mach bang nhau.
D. H i e u dien the hieu d u n g 0 hai dau dien t r o R nho h o n hieu dien t h e h i e u

pha so v o i dien ap 6 hai dau doan mach. M u o n xay ra hien t u o n g cong
h u o n g dien t r o n g mach phai

d u n g 6 hai d a u doan mach.

d o i d u g c . Bie't d u n g k h a n g ciia t i i dien bang R Vs . D i e u c h i n h L de dien ap

C. g i a m dien t r a cua mach.

hieu d u n g giua hai dau cuon cam dat cue dai, k h i do:

D. g i a m tan so d o n g dien xoay chieu.

A . dien ap giua hai d a u t u dien lech pha n/6 so v a i dien ap giCra hai dau

Cau 90: D u n g k h a n g cua m o t mach RLC mSc noi tiep d a n g c6 gla t r i n h o hon
cam khang. M u o n xay ra hien t u o n g cong h u o n g dien t r o n g mach ta phai

.

,7

C. Z L Z C = R

+Zc.

B. dien ap giua hai dau cuon cam lech pha n/6 so v o i dien ap giua hai dau
d o a n mach.

doan mach.

Cau 95 ( D H 2012): Dat dien ap u = Uocos2/rft vao hai d a u doan mach g o m
dien t r o thuan R, cuon cam thuan c6 do t u cam L va tu dien c6 dien d u n g C

L dat cue dai. Bieu thiic sai la
. v s . ; \m. :K '

' •

D. dien ap giua hai dau dien tro lech pha n/6 so v o i dien ap giua hai dau

T r o n g do U , m , R va C k h o n g d o i . Dieu chinh L de dien ap hieu d u n g tren

+

•

\ t r o n g mach c6 cong h u o n g dien.

Cau 9 1 : Dat dien ap u = uV2coscat vao hai dau doan mach R L C n o i tiep.

= U| +

I
f

.A f^S'i) ' T r ' ;

D. g i a m tan so d o n g dien xoay chieu.

A.

doan mach.
!

A . tang dien d u n g ciia t u dien.

:

:;

tiep g o m dien t r o t h u a n R, tu dien va cuon cam thuan c6 do t u cam L thay

B. tang he s o ' t u cam ciia cuon day.

C. g i a m dien t r o cua mach.

...

Cau 94 ( D H 2009): Dat dien ap u = UoCOscot vao hai d a u doan rr.ach mac noi

A . tang dien d u n g cua t u dien.

B. tang he so t y cam cua cuon day

.VfCi^i .

B. H i e u dien t h e t i i c t h a i 6 hai dau doan mach ciing pha v o i hieu dien the

»

Cau 89: D o n g dien xoay chieu t r o n g m o t mach RLC mac n o i tie'p d a n g cham

ii

h-'44rd i..'

A. C u o n g do hieu d i m g cua d o n g dien t r o n g mach dat gia trj I a n nha't.

'

,1 M L I

C. g i a m he so t u cam cua cuon day.

, -fi, ^ j

B. U [ - U C U L D. U^^ =

^

^

= 0.

^^l^.

—.

mac n o i tiep. Goi UK, U I , UC Ian l u g t la dien ap hieu d u n g giua hai dau dien
tro, giua hai dau cuon cam va giCia hai dau tu dim.

T r u o n g h g p nao sau

day, dien ap tiic t h a i giua hai dau doan mach cung pha v o i dien ap tuc thoi
giua hai dau dien tro?

Cau 92: Dat dien ap u = Uocoscot vao hai dau doan mach mac n o i tiep g o m dien
t r o thuan R, t u dien va cuon cam thuan c6 do tir cam L thay d o i dugc. Bict

d u n g k h a n g cua tu dien bang R^/3 . Dieu chinh L de dien ap h i ^ u dung
'

giira hai d a u cuon cam dat cue dai, k h i do
A . dien ap gii>a hai dau dien tro lech pha n/6 so v a i dien ap giua hai dau
doan mach.

B. Thay d o i R deUcnwx.

C. Thay d o i L de

D. Thay doi f de Ucnux.

Ui.nvix.

Cau 96 ( C D 2012): Dat dien ap u = U(icos((ot + (p) (voi Uu va (o k h o n g doi) vao
hai dau doan mach g o m bie'n tro niclc noi tiep v o i cuon cam thuan. Dieu
chinh bien t r a de cong sua't toa nhiet tren bien tro dat cue dai. K h i do
A . dien ap hieu d u n g giua hai dau bien t r o bang dien ap hieu d u n g giCJa hai

' B. dien ap giua hai dau t u dien l^ch pha n/6 so v a i dien ap giij'a hai dau
doan mach.
•
:;;,;,>::::270

A . Thay d o i C deUKni.vv.

••••

,

dau cuon cam thuan.
271


Bo

tr^ klen

thitc

V^t I I L T D t l tren

hinh

VTV2,

Cty

t^ip 2 - Chu Van Bl6n

B. dien ap hieu d u n g giua hai dau bien t r o bang hai Ian dien ap hieu d u n g
giiia hai d a u cuon cam thuan.
> ' '»
• '
C. he so cong suat cua doan mach bang 1.

n)

Cau 97 ( C D 2012): Dat dien ap u = U(icos(cot + cp) (Uo va (p k h o n g doi) vao hai

dau doan mach mac noi tiep g o m dien t r a thuan, tu dien va cucn cam thuan
CO do t u cam L thay doi duoc. K h i L = Li hoac L = L2 thi c u o n g d o d o n g dien
hieu d u n g t r o n g doan mach bang nhau. De c u o n g do d o n g d i e n hieu d u n g
trong doan mach dat gia t r i cue dai thi gia t r i cua L bang
A.i(L,+L2).

B . - ^ .

C . - ^ .

,

.
D.2(L,+L2).

Cau 98: Dat dien ap u = U()COs((iit + (\>) vao hai dau doan mcach c6 F,L,C mac noi
tiep. Bie't co^LC = 1. Dieu nao sau day k h o n g dung?

iJcb tf

iS: A . C u o n g do d o n g dien hieu d u n g trong mach Ion nhat

mach Ion nhat
ij; D . Dien ap tuc t h o i giCfa hai dau doan mach bang d i ^ n ap tuc : h 6 i g i i i a hai
'

'

Cau 99 ( C D 2009): Dat dien ap xoay chieu u = Uocos27:ft, c6 Uo k h o n g d o i va f
thay d o i d u o c vao hai dau doan mach c6 R, L, C mac noi tiep. K h i f = to thi

trong doan mach c6 cong h u o n g dien. Gia tri cua fo la

- A . -3=^
VLC

•

B.-S=.
N/LC •
'

C.-i=.
' VLC '

D' .271^V L C

•

d u o c ) vao hai dau doan mach g o m dien tro thuan, cuon cam thuan va tu
dien mac noi tie'p. Dieu chinh co = coi thi cam khang cua cuoxi cam thuan
bang 4 Ian d u n g khang cua tu dien. K h i co = 0)2 t h i trong mach xay ra hien
t u o n g cong h u o n g dien. He thuc d u n g la
B. a)2 = 2coi.

C.

ci)i=4co2.

au 102 ( D H 2009): Dat m o t dien ap xoay chieu co gia t r i hieu d u n g U vao hai
va tu dien co dien d u n g C mac no'i tie'p theo t h u t u tren. Goi Ui,, U R va Uc

Ian i u g t la cac dien ap hieu d u n g giiia hai dau m o i p h a n t u . Bie't d i e n ap
giua hai dau doan mach A B lech pha ^ so v o i dien ap giira hai dau doan
mach N B (doan mach N B g o m R va C ). He thuc nao d u o i day la dung?
A.

D . co2 = 4coi.

u = UN/2 cos(27rft) ( V ) , v o i U k h o n g doi con f thay d o i duoc. H i e n t u o n g
ifij,,;.-

; A . thay d o i do t u cam L de dien ap hieu d u n g giua hai dau cuon cam
(thuan) dat cue dai.
..

B. thay d o i dien d u n g C de dien ap hieu d u n g giCra hai ban tu dien dat cue
dai.
C . thay d o i R de cong suat tieu t h u tren doan mach dat cue dai.

272

+

B.

C. U ^ = U f ^ + U ^ + U ^

= U|+

+

.

D. U | = U ^ + U^+U2.

Cau 103 ( D H 2008): Doan mach dien xoay chieu khong phan nhanh g o m cupn

chay qua doan mach t h i he so'cong suat ciia doan

,1, a v i i j *.

mach nay
A. p h u thuoc dien t r a thuan ciia doan mach.

B. bang 0.

C p h u thuoc tong t r o cua doan mach

D . bang 1.

Cau 104: Doan mach xoay chieu g o m m o t cuon day mac noi tie'p v a i m o t t u
dien. D i e n ap hieu d u n g giira hai dau cuon day g i i i a hai ban t u hai dau
doan mach Ian l u o t la Ucd, Uc, U . Bie't U d = \Jcs[2

va U = Uc. I-Jhari xet nao
'"^'j^'i-^ "

A. C u o n day co dien tro thuan k h o n g dang ke va d o n g dien t r o n g mach
cung pha v o i dien ap giua hai dau doan mach.
B. C u o n day co d i e n t r o thuan dang ke va d o n g dien t r o n g mach v u o n g pha
vox dien ap giua hai dau doan mach.

C. C u o n day co dien t r o thuan dang ke va d o n g d i ^ n t r o n g m^ch c i i n g pha
v o i dien ap giiJa hai d a u doan mach.

''^ S>"'7'5 ^'•*> vfix iff.>II

D. D o U L > Uc nen Z L > Zc va trong mach k h o n g the thuc hi&n d u g c cong
huong.

Cau 101: Dat vao hai dau doan mach R L C mac n o i tie'p m o t dien ap xoay chieu
cong h u o n g dien xay ra k h i

= U| +

sau day la d u n g v o i doan mach nay?

Cau 100: ( C D 2012): Dat dien ap u = Uocos((ot + cp) (Uo k h o n g d o i , co thay doi

A . coi=2co2.

dai.

dien CO tan s o g o c

C. D o lech pha giua c u o n g do dong dien va dien ap gii>a hai dau doan

dau dien t r o R.

D. thay d o i tan so' f de dien ap hieu d u n g giCra hai dau dien t r a R dat cue

day CO do t u cam L, dien t r o thuan R va tu dien co d i e n d u n g C. K h i d o n g

PCM):* rlCii*

'{! B. Cong suat tieu thu cua doan mach la UoV 2R.
q

Vi^t

dau doan mach A B g o m cuon cam thuan co do t u cam L , dien t r o thuan R

D . he so cong suat cua doan mach bang 0,5.

'"

TNHH MTV D VVH Khang

'

'

^au 105: H e so cong suat ciia doan mach xoay chieu R, L, C k h o n g phan nhanh
CO

gia t r i cue dai k h i

A . tan so cua n g u o n xoay chieu bang tan so'rieng ciia mach.
B. do lech pha g i i i a c u o n g dp d o n g d i ^ n trong mach va d i ^ n ap g i i i a hai
dau mach bang 90".

' ^

C. chi k h i h i ^ u d i ^ n the giua hai ban t u dien co tr} so bang di?n ap ciia
nguon.

,,

'
273


Cty TIMll!

D. do lech pha giua cuong do dong dong dien trong mach va dien ap hg,

A. 3 U o 7 2 .

dau dien tro R bang 90".
C a u 106: K h i dien ap giua hai dau doan mach R L C mac noi tiep som pha 7t/4 so

^ ' ^ ^

VT^t

D. 4UoV2.

Cau 110: Mot dien tro thuan R mac vao mach dien xoay chieu tan so' 50 H z .

voi dong di^n trong mach thi

Muon dong dien trong mach som pha hon di?n ap giira hai dau doan mach

A. tan so ciia dong dien trong mach nho hon gia trj can xay ra hien tuorig

mot goc 7t/2, nguoi ta phai

cong huong.

"'V"*

A. mac them vao mach mot tu dien noi tiep voi dien tro.

B. tong tro ciia mach bang hai Ian thanh phan dien tro thuan R ciia mach.

D. dien ap giiia hai dau dien tro som pha

'''' '
•'

's

B. mac them vao mach mot cugn cam thuan noi tiep voi dien trc.

C . hieu so giij-a cam khang va dung khang bang dien tro thuan cua mach.

(lien.

B. 3Uo.

MTV D VV/f Khahg

C. thay dien tro noi tren bang mot tu dien.
D. thay dien tro noi tren bang mot cugn cam thuan.

so voi dien ap giua hai d a u tu

'

'

' *

Cau 111: Mach xoay chieu R L C c6 dien ap hieu dung a hai dau doan mach
'f*' "

khong doi. Hi^n tugng cong huong dien xay ra khi

...

A. thay doi R de dien ap hieu dung tren dien tro R cue dai.

C a u 107: K h i c6 cpng huong dien trong doan mach di|n xoay chiei; R L C thi

' '

B. thay doi tan so' f de dien ap hieu dung tren tu dat cue dai.

A. dDien ap tuc thoi giua hai dau dien tro thuan ciing pha voi dien ap tuc

•
'

'

C. thay doi dien dung C de dien ap hieu dung tren tu dat cue dai.

thai dat vao hai dau doan mach.

D. thay doi do tu cam L de dien ap hieu dung tren dien tro R drt cue dai.

B. di?n ap tuc thai giiia hai dau di^n tro thuan cung pha voi di?n ap tuc
thoi giiJa hai dau cuon cam.

Cau 112: Mach dien xoay chieu khong phan nhanh theo dung thu tu gom dien

JJ

tro R, tu dien C va cugn cam thuan c6 do tu cam L thay doi. Dieu chinh L de

C . dien ap tuc thai giiia hai dau dien tro thuan cung pha voi di$n ap tuc
thoi giiia hai ban tu dien.

dien ap hieu dung tren cugn cam dat gia tri cue dai thi di^n ap giua hai dau
^

D. cong suat tieu thu tren mach dat gia trj nho nhat.
Cau 108: Mgt mach di^n xoay chieu khong phan nhanh gom mpt cupn d a y

mach

W'

u = Uocoscot (voi Uo va co khong doi). Ket luan nao sau day la sai ve hien
tugng thu dugc khi thay doi C?
A. Den gia tri ma hieu dien the hieu dung tren tu dien dat gia Iri cue dai thi
mach dien c6 tinh dung khang.
B. Gia trj cue dai ciia hieu dien the hieu dung tren tu C dat dugc nho H o n
hoac bang gia tri hieu dung cua hieu dien the tren hai dau mach dien.
C . K h i xay ra cong huong thi hieu dien the tren tu di^n se vuong pha so v o i
hieu dien the tren hai dau mach dien
D. Voi gia trj cua C lam cho cong suat tieu thu tren cugn day d j t cue dai th'
dong dien trong mach se cung pha so voi hi^u dien the tren hai da>^'
mach dien.
C a u 109: Mot cugn day mac noi tiep voi tu dien c6 dien dung thay doi dugc l O '
mac vao nguon dien xoay chieu c6 bieu thuc u = UoCos(X)t(V). Thay d^'

4;
K

B. lech pha 71/2 voi dien ap tren L .

CO he so tu cam L , dien tro thuan R va mot tu dien C c6 dien dung thay
doi dugc. Dat vao hai dau mach mpt hieu di^n the xoay chieu xac d i n h

A. lech pha 71/2 voi dien ap tren doan L C .
C . lech pha 7i/2 voi dien ap tren C .

||,

D . lech pha Tt/2 voi dien ap tren doan R C .

'

^ C a u 113: Mach dien xoay chieu R L C noi tiep c6 dung khang Ian hon cam
khang. De c6 cong huong dien, ta c6 the
A. giam dien dung cua tu dien.
B. giam he so'tu cam ciia cugn day.

•
.*J51 I H

C. tang dien tra thuan cua doan mach.
D. tang tan so'dong dien.

Cau 114: Mach dien xoay chieu khong phan nhanh theo diing thu tu gom tu
di^n C , dien tra R va cugn cam thuan L . Dieu chinh C de di?n ap hi^u dung
tren tu dat gia tri cue dai thi dien ap gii>a hai dau mach
A. vuong pha voi di^n ap tren doan R L .

o'; '

B. vuong pha voi dien ap tren L .

: *)£,'

C. vuong pha vdi dien ap tren C .

-

n

D. vuong pha voi dien ap tren doan R C .

dien dung cua tu dien de cong suat toa nhi^t tren cugn day dat cue dai th'

jCau 115: Trong doan mach R L C noi tiep dang xay ra cong huong. Tang dan

khi do dien ap hieu dung tren hai ban tu la 2Uo. Di^n ap hieu c'ung giua h'^'

tan so'dong dien, giCr nguyen di^n ap hieu dung giua hai dau doan mach va

dau cugn day liic nay la

giu nguyen cac thong so'cua mach, ket luan nao sau day khong diing?

'

•!

n

• •••no-ii^n

275


B S trp MSn thiSrc V$t H LTDH tren hgnh

:

VTV2. t^p 2 - Chu

VSn

Bign

C a u 121: C h o n phat bieu dung? M o t t r o n g n h u n g u u d i e m cua may bie'n the

A . H e so'cong suat ciia doan mach giam.

t r o n g sir d u n g la

B. C u o n g do hieu d u n g cvia d o n g dien g i a m .

A . k h o n g birc xa song dien tir.

t

C. D i e n ap hieu d u n g g i i i a hai ban tu dien tang.

4^5,

jv^j /;

, ,

"

'"Mg

B. k h o n g tieu t h u d i e n nang.

.,

D . D i e n ap hieu d u n g giiia hai dau dien t r o g i a m .

sul

/» v 6 h

"-''^f'''

•-^'^^^

C. Co the tao ra cac hieu dien the'theo yeu cau sir d u n g .

C a u 116: T r o n g m o t doan mach d i e n xoay chieu RLC mac noi tiep, k h i xay ra
cong h u o n g t h i phat bieu nao sai?
A . D i e n ap tuc t h o i tren doan mach bang dien ap tuc t h o i tren d i ^ n t r o .
B. T o n g d i e n ap tuc t h a i tren tu dien va tren cuon cam bang 0.

,.||| ,

D . K h o n g C O s u hao p h i nhiet do d o n g dien Phuco.

f»'ht

" ' ' ' • ''
• *

C a u 122: C h o n phat bieu d u n g ?

'
^'^^
A . C h i CO d o n g dien ba pha m o i tao ra tir t r u o n g quay.

'

'

8'"'^'
• "'

B. Roto ciia d o n g eo k h o n g d o n g bo quay v o i to'c d p g o t cua tir t r u o n g

C. T o n g d i e n ap h i ^ u d u n g tren tu dien va tren cuon cam bang 3, ,j
D . D i e n ap hieu d u n g gii>a hai dau doan mach bang d i f n ap h i f u d u n g tren

SO.

C a u 117: T r o n g mach dien xoay chieu RLC n o i tiep d a n g c6 cong h u o n g dien
t h i ket l u a n nao sau day SAI?

d a u t u d i e n . ,f-, ^ ( \
rtq
unoM
B. C u o n g d o hieu d u n g t r o n g mach cue d a i .

imiti

veox ft^ib r{:'f,M :Sri

C. D i e n ap hieu d u n g 6 hai dau doan mach I o n h o n d i e n ap hieu d u n g 6 hai
dau d i e n t r o R.

C a u 118: T r o n g m o t d o a n mach dien xoay chieu RLC mac noi tiep, k h i xay ra
cong h u o n g t h i phat bieu nao sau day sai?

i \ <5»'K| fij-^|\

A . D i e n ap tuc t h o i tren doan mach bang d i e n ap tuc t h o i tren d i e n t r a .
B. Tong d i e n ap tuc t h o i tren tu dien va tren cuon cam bang 0.

. • ,

C. T o n g dien ap hieu d u n g tren t u dien va tren cuon cam bang 0.
D . D i e n ap hieu d u n g g i i i a hai dau doan mach bang d i ^ n ap hi-^u d u n g tron
di#n t r o .
C a u 119: T r o n g d o a n mach xoay chieu, d o n g dien va hieu d i e n the' c u n g pha
Chi

khi

:

A

i/j

A . Trong mach xay ra cong h u o n g dien. .f uyii-?

an-

B. C o n g suat tieu t h u trong mach cue d^Liir
C. D o a n mach chi C O d i e n t r o t h u a n .

"'

'

'

'

A . Tir t r u o n g tong h g p quay v o i toe d o l u o n nho h a n tan so goe eiia d o n g
B. N g u y e n tac boat dong dua tren hien t u g n g cam irng dien tir va sir d u n g tir
•

' -

.

r ;>

•

C. Stato CO 3 cuon day g i o n g nhau qua'n tren 3 loi sat b o ' t r i lech nhau 1/3
d u o n g tron.
D. Tir t r u o n g quay dugc tao ra boi d o n g dien xoay chieu 3 pha.
Cau 124: M o t may phat dien xoay chieu mot pha co dien tro trong khong dang ke,
mac vao doan mach noi tie'p RLC. K h i toe do quay ciia roto bang n l trong
mach RLC co cong h u o n g va euong do hieu d u n g trong mach liic nay la I I . K h i

toe do quay ciia roto bang n2 thi euong dp hieu d u n g trong mach cue dai la 12.
Chon he thire d u n g .
A. n| = i i . .

'" •
B. n | < n 3 .

C. I 2 < I | .

"-"
D. n | > n 2 .

Ian ma k h o n g thay d o i cong suat truyen d i , ta can ap d u n g bien phap nao
neu sau day?

'

D . T r o n g mach chi eo dien t r o thuan hoae c6 xay ra cong h u o n g d i e n . /
ap?
A . D u n g l o i sat C O d i ^ n t r o suat nho.

Cau 123: C h o n cau sai k h i noi ve d o n g co k h o n g d o n g bo 3 pha

C a u 125: De g i a m cong suat hao p h i tren m o t d u o n g day tai d i e n x u o n g bon

C a u 120 : Bi§n phap nao sau day khong gop p h a n tang hieu suat ciia may bie'n

n?

. . .

D. Toe d o goe ciia d o n g co k h o n g d o n g bp p h u thuoe vao to'c d o quay ciia

t r u o n g quay.

D . D i e n ap hai d a u mach c i i n g pha v o i dien ap hai dau d i e n t r o K

•ri

•

tir t r u o n g va vao m o m e n can.

A . D i e n ap hieu d u n g a hai dau cuon cam bang dien ap h i ^ u d u n g gii>a hai

,

C. Vecto cam i r n g tir ciia tir t r u o n g quay l u o n thay d o i ve ca h u o n g Ian trj
A'

dien t r o .

' '• '

A . Tang dien ap giua hai dau day tai t r a m phat dien len b o n Ian. ( I
B. Tang dien ap giua hai dau day tai t r a m phat d i e n len hai Ian.
C. G i a m d u o n g k i n h tiet dien day d i bon Ian.

*•

B. D i m g day c6 d i e n t r o suat nho l a m day quan bie'n ap.
C . D i m g l o i sat g o m nhieu la sat m o n g ghep each d i e n v o i n h a u .
D . Dat cac la sat cua l o i sat song song v o i mat phang ehua cae d u o n g sue tii^

'

D . G i a m dien t r o d u o n g day d i hai Ian.
C a u 126: De g i a m bat hao p h i d o toa nhiet tren d u o n g day k h i can tai dien d i
xa. T r o n g thuc te^ eo the d i i n g bien phap
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A. g i a m hieu d i e n the may phat dien n Ian de g i a m cirang do d o n g dien

C. cong
con} suat tieu thu dien h u u ich tang.

dien tren d u o n g day n Ian.

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B. ccuoi
u o n g d o d o n g dien hieu d u n g tang.

tren day n Ian, g i a m cong suat toa nhiet x u o n g n^ Ian.
B. tang hieu d i e n the 6 n o i san xuat dien len n Ian de g i a m c u a n g do dong

'

,

,

j

D . cong suat tieu t h u P giam.

CaU 132: Goi N i la so v o n g day ciia cuon so cap, N2 la so v o n g day cua cugn

C. D i i n g day d a n bang vat lieu sieu dan d u o n g k i n h Ion.

t h u cap cua m o t may bien ap. Bie't N i > N2, may bien ap co tac d u n g

D. Xay d y n g nha m a y gan n o i tieu t h u dien de g i a m chieu da: d u o n g day

A. tang cuong dong dien, giam dien ap.

t r u y e n tai dien.

,.,,,,,,^,1,,,,^.,,:,,„

.

B. giam cuong do dong dien, tang dien ap.

.

Cau 127: D i e u khang d j n h nao sau day la d u n g k h i n o i ve may bien ap?
A. M a y bien ap c6 the lam thay d o i dien ap cua d o n g dien m o t d i i e u .

*'''
,

D. giam cuong do dong dien, giam dien ap.
Cau 133: Goi fi, ii,

C. N e u so v o n g day cuon so cap Ion h o n s o v o n g day cuon t h u cap t h i goi la
may ha ap.

' ^-' '

C tang cuong do dong dien, tang dien ap.

B. M a y bien ap c6 tac d u n g lam thay doi tan so cua d o n g dien xoay chieu.
,

Ian l u g t la tan so d o n g dien xoay chieu ba pha, tan so'ciia

t u t r u o n g , tan so ciia roto trong dong co k h o n g d o n g bo ba pha. Ke't luan
nao sau day la d u n g k h i noi ve mo'i quan he giua cac tan so'

D. N e u so v o n g day cuon so cap Ion h o n so'vong day cuon t h u cap thi goi la

A.fl

= f2 = f3.

C. fl = f 2 < f 3 .

may tang ap.

B.f,

= f2>f3.

--,v'-'^^#*-*'>^

D . f l > f 2 = f3.

V'tJ.

Cau 134: K h i d o n g co k h o n g d o n g bo ba pha hoat d o n g o n d j n h v o i toe do

Cau 128: D i e u nao sau day la sal k h i noi ve d o n g ca k h o n g d o n g bo ba pha?
A. Co hai bo phan chinh la Stato va Roto.

quay cua t u t r u o n g k h o n g d o i thi to'c do quay ciia roto

B. Bien d o i dien nang thanh nang l u o n g khac.

A. Ion h o n toe do quay cua t u t r u o n g .

C. T u t r u o n g quay trong d o n g co la ke't qua cua viee sir d u n g d o n g dien

B. l u o n bang toe do quay cua t u t r u o n g .

•

C. nho h o n toe do quay cua t u t r u o n g .

xoay chieu m o t pha.
D. H o a t d o n g d u a tren co so hien t u g n g cam u n g d i e n t u va s u d u n g t u

t r u o n g quay.

,

'

D. CO the Ion h o n hoac bang toe do quay cua t u t r u o n g , t u y thuoc tai.
Cau 135: K h i cho d o n g dien k h o n g d o i qua cuon so cap cua m a y bien ap t h i

: ,,|,v,,>,., „;;:',,,„

trong mach k i n cua cuon t h u cap

Cau 129: D i e u nao sau day la sai k h i noi ve ttong co k h o n g d o n g bo ba pha?
A. Toe do goc khi da on dinh cua khung day luon nho hon toe do goc cua t u
truong quay.
B. K h o n g the thay d o i chieu quay cua d o n g co chi bang viee dao v i t r i ba
pha d u a vao ba cuon day tren Stato.

A. CO d o n g dien xoay chieu chay qua.

'

B. CO d o n g dien m o t chieu chay qua.

'

C. CO d o n g dien k h o n g d o i chay qua.

'

'"

"

D. Vi^c d u a d o n g t h a i ba pha cua d o n g dien xoay chieu ba pha vao ba cuon

'

t r u o n g quay t r o n g d o n g co co tan so

' ' ^

A. bang tan so'ciia d o n g dien chay t r o n g cac cuon day ciia stato.

cua d o n g dien xoay chieu d u a vao.

B. Ion h o n tan so'ciia d o n g dien chay t r o n g cac cuon day ciia stato.

,,

Cau 130: D o n g dien 3 pha mclc h i n h sao co tai do'i x u n g g o m cac b o n g den. N e u
d u t day t r u n g hoa thi cac den co do sang
.

B. k h o n g d o i .

, T

Cau 136 ( C D 2009): K h i d o n g co khong d o n g bo ba pha hoat d o n g o n d j n h , t u

day tren Stato la de tao ra t u t r u o n g quay v o i tan so quay bang tan so'

A. tang.

,'

D. k h o n g CO d o n g dien chay qua.

C. D o n g CO hoat d o n g d u a tren nguyen tac cua hien t u g n g cam u n g d i e n t u .
isn

TlStin

'

C. CO the Ion h o n hay nho h o n tan so'ciia d o n g dien chay t r o n g cac cuon day
ciia stato, t u y vao tai.

.

C. giam.

'

D . k h o n g sang.

D. nho h o n tan so'ciia d o n g dien chay trong cac cuon d i y ciia stato.
co

Cau 137: K h i truyen tai m o t cong suat dien P t i l noi san xua't den noi tieu thu, de

d i e n . . . v o i cong suat d j n h m u c P va dien ap d j n h m u c U , neu nang cao h$ so

giam hao p h i tren d u o n g day do toa nhiet thuc te'nguoi ta tie'n hanh lam n l i u

cong suat thi lam cho

the nao?

Cau 131: D o i v o i cac d u n g cu tieu thu dien n h u quat, tu lanh, d o n g

A. cong suat toa nhiet tang.

MV,,;, ;^ r

- ?

A. Dat o d a u ciia nha may dien may tang the'va a noi tieu thu may ha the.
279


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B. D a t 6 dau ra ciia nha may dien may ha the va dat 6 n o i tieu t h u may
t h e h o a c tang the'tuy vao n h u cau t u n g dja p h u a n g .

C a u 143: Phat bieu nao sau day d u n g v o i may phat d i e n xoay chieu?
A . D o n g dien cam u n g chi xua't hien a cuon day cua p h a n u n g , k h o n g the

C. C h i can dat 6 dau ra cua nha may dien may tang the, dieri tren d u o n u
day d u g c s u d u n g true tie'p ma k h o n g can m a y bien the.

xua't hien 6 cuon day cua phan cam.
B. Tan so ciia sua't d i e n d p n g t i le v o i so v o n g day ciia p h a n u n g .

D . Dat 6 dau cua nha m a y dien may tang t h e v a dat 6 n o i tieu t h u may
the hoac tang the'tuy vao n h u cau t u n g dja p h i r o n g .

C. Bien d o ciia sua't d i e n d o n g cam u n g t i le v o i so v o n g day ciia phan l i n g .
D . Co nang c u n g cap cho m a y d u y c bie'n d o i hoan toan t h a n h diijn nang.

C a u 138 ( C D 2012): M o t m a y phat dien xoay chieu m o t pha c6 phan cam jg

C a u 144: Phat bieu nao sau day la d i i n g k l i i noi ve may phat dien xoay chieu ba

roto va so'cap cue la p. K h i roto quay deu v o i toe do n (v6ng/s) t h i t u thong

pha.

qua m o i cuon day cvia stato bie'n thien tuan hoan v o i tan so ( t ' n h theo don

A . M a y phat dien xoay chieu ba pha bien dien nang thanh co nang va ngugc

,

viHz)la

.

A.

lai.
B. M a y phat d i ^ n xoay chieu ba pha hoat dong nho hien t u g n g cam u n g dien

60

,,

B. — .
60p

C.60pn.
^

D.pn.

^

. , ^

C a u 139: M o t may tang ap c6 cuon t h i i cap mac v o i dien t r a t h u a n , cuon so cap

do, c u n g tan so'va cung pha.

mac vao n g u o n d i e n xoay chieu. Tan so'dong dien t r o n g cuon thi'r ca'p
A . l u o n Ion h o n tan so d o n g dien trong cuon so cap.

^,

C. bang tan so d o n g d i e n t r o n g cuon so cap.

C a u 145 ( D H 2008): Phat bieu nao sau day la d i i n g k h i noi ve d o n g d i ^ n xoay

'

chieu ba pha ?

D . CO the n h o h o n hoac Ion h o n tan so d o n g dien t r o n g cuon so r a p .
C a u 140: M o t m a y bie'n the'co t i so'so v o n g day ciia cuon so cap va t h i i cap la
...

>i

m o t pha, lech pha nhau goc —

D . g i a m hieu dien the'lO Ian va tang c u o n g do d o n g dien 10 Ian.

C a u 141: N h a n xet nao sau day ve may bien the la k h o n g diing?

^ ,

A . M a y bien the'co the tang hieu dien the xoay chieu.

j^

B. M a y bien the'co the g i a m hieu dien the xoay chieu.

,

,

,

A . Sua't d i e n d o n g ciia may phat dien xoay chieu ti le v o i toe d o quay cua

C a u 146: Phat bieu nao sau day la diing?

B. N g u o i ta CO the tao ra tir t r u o n g quay bang each cho d o n g dien xoay
chieu chay qua n a m cham dien.
C. N g u o i ta CO the tao ra tir t r u o n g quay bang each cho d o n g dien xoay

roto.
B. D o n g dien xoay chieu m o t pha chi c6 the do may phat d i e n xoay chieu
m o t pha tao ra.

chieu m o t pha chay qua ba cuon day cua stato ciia d o n g co k h o n g dong
bg ba pha.

C. D o n g d i e n d o may phat dien xoay chieu tao ra l u o n c6 tan so bang so

D . N g u o i ta CO the tao ra tir t r u o n g quay bang each cho d o n g d i e n xoay
chieu ba pha chay qua ba cuon day cua stato cua d o n g co k h o n g d o n g bo

v o n g quay t r o n g m o t giay cua roto.
280

t r o n g hai pha con lai cue tieu.

chieu chay qua n a m chain dien.

D . M a y bie'n the'co tac d u n g bie'n d o i c u o n g d o d o n g dien xoay chieu.

D . C h i CO d o n g xoay chieu ba pha m o i tao ra d u g c tir t r u o n g quay.

D . K h i c u o n g d g d o n g dien t r o n g mot pha cue dai t h i c u o n g cig d o n g dien

A . N g u o i ta CO the tao ra tit t r u o n g quay bang each cho d o n g dien mot

C. M a y bie'n the'co the thay d o i tan so d o n g dicMi xoay chieu.
Cau 142: Phat bieu nao sau day dung?

, ,.

C. D o n g dien xoay chieu ba pha la he thong g o m ba d o n g dien xoay chieu

fh '|h

C. tang hieu d i e n the'lO Ian va giam c u o n g do d o n g d i e n 10 Ian.

,

., ,,,,, ..-^

B. C h i CO d o n g dien xoay chieu ba pha m o i tao dugc t u t r u o n g quay

. - ,-r

B. g i a m hieu dien t h e v a d o n g d i e n 10 Ian.

A . K h i c u o n g d o d o n g dien t r o n g m o t pha bang k h o n g t h i c u o n g do d o n g
dien t r o n g hai pha con lai k h a c k h o n g

1 :10. Bo qua hao p h i 6 m a y bien the. D u n g m a y bie'n the nay c6 the
A. tang hieu d i e n t h e v a d o n g dien len 10 Ian.

D . M a y phat dien xoay chieu ba pha hoat d o n g n h o viec su d u n g t u t r u o n g
quay.

B. l u o n nho h o n tan so d o n g dien trong cuon so cap.
,

C. M a y phat d i e n xoay chieu ba pha tao ra ba d o n g d i e n m o t pha c u n g bien

j: ^,

bapha.

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Cau 147: Phat bieu nao sau day d u n g do'i v a i may phat d i e n xoay chieu m o t

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D . de g i a m to'c do quay ciia ro to n g u o i ta g i a m so'cuon d a y va g i a m so cap
cue t u .

plia?
A . Bien do cvia suat dien d o n g p i i u thuoc vao so cap cue ciia n a m chiam.

Qli\x 152: T r o n g he t h o n g t r u y e n tai d o n g ba pha d i xa theo each mac h i n h sao

B. Tan so ciia sua't dien d o n g p h u thuoc vao so v o n g day ciia phan u n g .

thi:

C. D o n g dien cam u n g chi xuat hien 6 cac cuon day ciia phan l i n g .

A . C u o n g do hieu d u n g ciia d o n g dien t r o n g day t r u n g hoa b^ng t o n g cac

D . N e l l phan cam la n a m cham dien thi n a m cham do d u g c n u o i b o i d o n g
d i ^ n xoay chieu

" '''

-.J^ •

Cau 148: Phat bieu nao sau day la sai? T r o n g qua t r i n h t r u y e n tai dien nang d i

c u o n g do hieu d u n g ciia cac d o n g dien trong ba day pha.
B. D o n g dien t r o n g m o i day pha deu lech pha 2A,/3 so v a i dien ap g i i i a day
pha d o va day t r u n g hoa.

xa, cong sua't hao p h i tren d u o n g day tai dien ti 1|

C. C u o n g do d o n g dien trong day t r u n g hoa l u o n bang 0.

A . v o i t h o i gian t r u y e n dien.

D . D i e n ap hieu d u n g g i i i a hai day pha Ian h o n dien ap hieu d u n g giira m o t

B. v o l chieu dai du'ong day tai dien.

?

" ,

C. v o i b i n h p h u o n g cong sua't truyen d i .
D . nghjch v o i b i n h p h u a n g dien ap giCra hai dau day 6 t r a m phat dien.
Cau 149: Phat bieu nao sau day ve d o n g co k h o n g d o n g bo ba pha la sai?
A . Roto cua d o n g co quay v o i toe do goc nho h a n toe do goc cua tir t r u o n g
quay.
C. N g u y e n tac hoat d o n g cua d o n g co dua tren hien t i r g n g cam u n g dien tu
va su' d u n g t u t r u o n g quay.
D . Vecto cam u n g t u cua tCf t r u a n g quay t r o n g d o n g ca l u o n thay d o i ve ca
h u o n g va t r i so.
' 'j' v

''

d o n g bo ba pha CO do Ion k h o n g d o i .
d o n g bo ba pha co p h u o n g k h o n g d o i .
C. C a m u n g t u do ca ba cuon day gay ra tai tam stato cua d o n g co k h o n g
d o n g bo ba pha co h u o n g quay deu.

i

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C. bang tan so goc ciia d o n g dien.

'

'

•4

D. Ion h o n tan so'goc ciia d o n g dien.
A . g i a m hao p h i d i e n nang tren d u o n g day tai dien.

v ''

B. tang cong sua't n g u o n dien.

.• ': i

C. g i a m cong sua't 6 n o i tieu thu dien.

„

D . tang tie't dien ciia day tai dien.

;

.

r

J

:.

A . C a m l i n g dien t u .

B. Cong h u o n g d i ^ n t u . "

C . H i e n t u g n g t u tre.

D. Cam ling t u .

,

;

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A . phan cam la bo phan d u n g yen, phan l i n g la bo phan chuyen d o n g .
B. phan cam la bo phan chuyen dong, phan l i n g la bo phan d i r n g yen.
C. ca p h a n cam va phan u n g co the cung d i i n g yen, hoac cung chuyen dong,
n h u n g bo gop dien thi nhat d j n h phai chuyen dong.

D . Cam u n g t u do ca ba cuon day gay ra tai tam stato cua d o n g co k h o n g
d o n g bo ba pha co tan so bang tan so d o n g dien.
Cau 151: T r o n g may phat dien xoay chieu mot pha v o i tan s o k h o n g d o i
A . de g i a m to'c do quay cua ro to n g u o i ta g i a m so'cuon day va tang so'cap

D. tuy thuoc cau tao cua may, phan cam cung n h u p h a n l i n g co the la bo
phan d i i n g yen hoac la bo phan chuyen d o n g .
C a u 157: M o t nha m a y cong nghiep d u n g dien nang de chay cac d g n g co. He
so cong sua't ciia nha may do N h a nuoc quy d j n h phai I o n h a n 0,85 n h a m
muc d i c h chinh la de

cue t u .
B. de g i a m toe do quay cua ro to n g u o i ta tang so cuon day va g i a m so cap

A . nha may san xua't nhieu d u n g cu.
B. d o n g C O chay ben h o n .

cue t u .
C. de g i a m toe d g quay cua ro to n g u o i ta tang so'cupn day va tang so'cap

,

-••'••'k

B. bien d o i dieu hoa theo t h a i gian.

C a u 156: T r o n g may phat dien

B. C a m u n g tir do ca ba cuon day gay ra tai t a m stato cua d o n g ca k h o n g

282 " ,

A . nho h a n tan so goc ciia d o n g dien.

C a u 155: C o so hoat d o n g ciia may bien the'Ia gi?

A . Cam u n g t u do ca ba cuon day gay ra tai tarn stato ciia d o n g ca k h o n g

cuctu.

C a u 153: T r o n g d o n g co k h o n g d o n g bo ba pha, t u t r u o n g quay v o i toe d g goc

C a u 154: T r u y e n tai dien nang d i xa phai d u n g may bien ap tang the'Ia de

B. H a i bo phan c h i n h cua d o n g co la roto va stato.

Cau 150: Phat bieu nao sau day la k h o n g dung?

day pha va day t r u n g hoa.

•

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C. nha may s i i d u n g nhieu dien nang.

, '

' "''

'

D . bot hao p h i d i e n nang tren d u o n g day dan dien den nha m a y .
283


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C a u 158: M o t n h a m a y c o n g n g h i e p d i i n g d i e n n a n g d e c h a y cac d o n g c o . H o
so c o n g s u a t c u a n h a m a y d o N h a n u o c q u y d j n h p h a i I o n h o n 0,85 nhan-,

dac d i e m sau h o n h a n d o n g xoay chieu 1 p h a .

A . n h a m a y san xuat nhieu d u n g cu.

A . Tiet k i e m d u o n g d a y t r o n g k h i tai d i e n .

.,f;;K-vir,>

••^•^y•

C. n h a m a y sir d u n g n h i e u d i e n nang.
D . b a t h a o p h i dien nang tren d u o n g day d a n dien den n h a m a y .

-.

C . r o t o q u a y v a i t a n s o I a n h o n t a n so q u a y c u a t u t r u a n g .
D . roto quay n g u g c chieu quay cua t u t r u a n g .
Cau

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D . M a y c o c a u tao don g i a n .

'

2 0 0 9 ) : T u t h o n g qua mpt v o n g d a y dan l a (f) = (20/Tr)cos(1007tt +

7i/4) ( W b ) . B i e u t h i i c c u a s u a t d i e n d o n g cam u n g xuat h i e n t r o n g v o n g d a y

A. roto quay k h o n g d o n g deu khi nhanh khi cham.
B. r o t o q u a y v o i t a n s o n h o h a n t a n s o q u a y c u a t u t r u a n g .

O c rrir.! o > i j -.(fi • . '

C. T a o dupe tu truong quay.
Cau 1 6 4 ( D H

C a u 159: T a g o i d o n g c a s i f d u n g t i r t r u o n g q u a y l a k h o n g d o n g b e v i

Vift

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B. K h o n g c a n bp g o p k h i che'tao may p h a t d i e n .

; ' •;

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au 1 6 3 : V i e c t a o r a d o n g d i e n x o a y c h i e u 3 p h a c o u u d i e m n a o t r o n g so cac

m u c d i c h c h i n h la d e

B. d p n g CO c h a y b e n h a n .

TNIIH nrv

nay l a

«

A . e = -2sin(100Kt + K / 4 ) ( V ) .

B . e = 2sin(1007it + 7r/4) ( V ) .

C.e = -2sinl007it(V).

D . e = 27Tsinl007tt ( V ) .

,

160: T r o n g d o n g c o k h o n g d o n g b o b a p h a , n h a n d j n h n a o s a u d a y 1^

DAP

dung?
A . K h i boat d o n g d j n h m u c thi roto l u o n k i o n quay d e u .

AN

•

lA

28

38

4D

5D

6A

7D

8D

98

lOB

B. T o e d o g o c c u a r o t o b a n g t a n so g o c c i i a t u t r u o n g q u a y .

IIB

12D

13A

14A

158

168

178

18D

19C

20D

C. R o t o k h o n g q u a y d e u , toe d o g o c t r u n g b i n h n h o h a n t a n so g o c c u a tu

21D

22C

23A

24C

25A

26A

27C

28C

29D

30C

31B

32D

33D

34D

358

368

37C

38D

39A

408

418

42C

43A

44C

45C

46D

47C

488

49C

50C

51B

52A

53D

548

55C

56D

57A

58C

59D

60A

61B

62C

63C

64C

65A

66C

67C

688

69C

708

71A

72C

73B

74D

75C

76A

77C

78D

798

80C

truang quay.

n ' ^ n "']-^:

'•'-t

)

D . T o e d o g o c CO t h e I a n h a n h a y n h o h o n m o t e a c h b a t k i , p l i u t h u o c vac
c o n g s u a t c u a d o n g CO.

.i.:;Hhi)iii

uyu

yytnuc

^inx}

fimt;^

C a u 1 6 1 : D o n g c a n a o t r o n g cac t h i e t b j s a u d a y l a d o n g c o k h o n g d o n g b o ?
A . xe d i e n .

B. m o t o c u a d a u d i a D V D .

C. q u a t d i e n g i a d i n h .

D . tau dien.

T r o n g m a c h d i e n x o a y c h i e u ba p h a , t a i m a c h i n h sao, k h i m p t pha t i e u thu
d i e n b i chap t h i c u o n g d o d o n g d i e n t r o n g hai pha e o n lai

' Rnoi'f

A . deu tang len.
B. d e u k h o n g t h a y d o i .

:t»c;

82A

83A

84C

85D

86D

87D

88A

89D

90D

92A

93D

94D

95A

96A

97A

98C

99D

100 A

lOlD

102C

103D

104C

105 A

106C

107A

1088

109A

HOC

HID

112D

113D

114A

115C

116C

117C

118C

119D

120A

'i

121C

122D

123A

1248

1258

1268

127C

128C

1298

1308

i q

131C

132 A

1338

134C

135D

136 A

137A

138D

139C

HOC

141C

142A

143C

1448

145A

146D

147A

148A

149D

1508

151C

152D

153C

154 A

155A

156D

157D

158D

1598

160C

161C

162D

163A

1648

C. p h a n a o eo t o n g t r a n h o h o n t h i c u o n g d o d o n g d i e n t a n g ! e n v a nguoi^

D. deu giam xuong.
Cau

SIC
91A

162: T r o n g m a n g d i e n 3 p h a t a i d o i x u n g , k h i c u o n g d o d c n g d i e n qi^''^

m o t p h a la c u e d a i t h i d o n g d i e n q u a h a i pha k i a n h u t h e nao?
A . C o c u a n g d o b a n g 1/3 c u o n g d o c u e d a i , c u n g c h i e u v o i d o n g t r e n .
B. C o c u a n g d o b S n g 1/2 e u a n g d p c u e d a i , c u n g c h i e u v o i d o n g t r e n .
C. C o c u o n g d o b a n g 1/3 c u o n g d o c u e d a i , n g u o e c h i e u v o i d o n g t r e n .
D . C o c u o n g d p b a n g 1/2 c u o n g d p c u e d a i , n g u p c c h i e u v a i d o n g t r e n .

• •V.firn

mlh ni-h''('^h ^inrjvi

./vj
285


Bo trfi kicn

thiic

V$t liLTDH

tren kenh

VTV2. t^p 2-

cty r/m/i nrv o VVH nnang

Chu V^n Bl^n

Cau 3: Mach gom dien tro R = 100 Q mSc noi tiep voi cuon day thuan cam
L = 1/71 H. Dien ap dat vao hai dau doan mach co dang u = 400cos2507it (V).
Cuong dO dong dien hieu dung qua mach co gia tri bang
A. 1 A.
B. 3,26 A.
C. (2 + V2 ) A.
D.
A.

BAI TAP D|NH LI/0NG
Cau 1: Doan mach AB gom cuon cam thuan no'i tiep voi tu dien. Dat nguon
xoay chieu co tan so goc co vao hai dau A va B tlii tu dien co dung khang
100 Q, cuon cam co cam khang 50 Q. Ngat A, B ra khoi nguon va tang do tu
cam ciia cuon cam mot lugng 0,5 H roi noi A va B thanh mach kin thi tan so
i goc dao dong rieng cua mach la 100 (rad/s). Tinh a).
.(}. A. 8071 rad/s.
B. 507t rad/s.
C. 100 rad/s.
D. 50 rad/s.
Huang dan
50
' 1,
.
.„
Z L = coL = 50Q => L =
• = L'C = (L + AL)C
1
1
On
Zr =
= 100Q=>C = coC
lOOco
50 1
1
1
1 1
1 1
1

• + 0,5.• = 0=>co = 100(rad/s)

Huang dan

0) 100(0

100©

loi^

2 0 0 CO

10000

^

Ui
Dong 1 chieu : Ij =
Dong xoay chieu : I2 =

U A M I U MB

tan 9AM tancpMB = - 1 :
(R

coscpi

=C0S(P2

L = CR^

-Zc
R

+ r)

<=>

#

+ r)^

(OiL--

1

(R

+ r)2 +

1

•=R
cojC

=^LC =

100^y2

U 2 _

^ R 2 + Z^L

C02C

C02_

L - rRC ^ -

: - l = > U AM J- " M B

= Z T Z C = rR

C

r
"MB

AM

R

2

30

= 1

+ u 0MB

/

+

UoAM-50(V)

2
2
U o A M +Uo^

3=100^ '

).„.:.!*•••

lOOV

cOjL = R

2

UQMB;

—

CO2CO2

40V3^

,UOAM.

u^jyl tre pha hcjn U^B 1^ — => " A M - 50cos
3

A

0)1

- = 1A

Vl 00^+100^
'

0AM;

(02L-

(OiC

= 2A

VlOO^ + 0

,L

Huang dan

O A M

(R

200

Cau 4: Dat dien ap u = 100cos(cot + 7c/12) (V) vao hai dau doan mach AB gom
hai doan AM va MB mac noi tiep. Doan AM gom tu di^n co di?n dung C
no'i tiep voi dien tro R va doan MB chi co cuon cam co dien tro thuan r va co
do ty cam L. Biet L = rRC. Vao thoi diem to, dien ap giu-a hai dau cuon cam
bang 40 >/3 V thi dien ap giiia hai dau mach AM la 30 V. Bieu thuc cua dien
ap giiia hai dau doan mach MB C O the la
«
i
A. U A M = 50cos(cot-57t/12)(V).
'
B. U A M = 50cos(cot - 7t/4) (V).
C. U A M = 200cos(cot - 7i/4) (V).
D. U A M = 200cos(cot - 57t/12) (V).

y

R^
(R + r)

_

: ^ i = 7 i i + I 2 =V5(A)

= -1:

r

U_

Z2

'

Cau 2: Dat dien ap u = 125 \/2 coscot (V), co thay doi dugc vao doan mach noi
tiep AMB. Doan mach AM gom dien tro R noi tiep tu dien, doan mach MB
chua cuon day co dien tro r. Biet dien ap tren doan AM luon vuong pha vol
dien ap tren doan MB va r = R. Voi hai gia tri co = IOOTT rad/s va co = 56,257:
rad/s thi mach AB co ciing he so'cong suat va gia tri do bang
A. 0,96.
B. 0,85.
C.0,91.
D. 0,82.
Huong dan

,

u = 400cos^ (507tt)= 200 + 2Q0cos(1007ct)

••

10000

vift

n

Uo:4B=50V3(V)
7tV

12 3

(V)

I
3

C02

• cos (pj = •

(R + r)
(R + r)^ + R

COi
CO,

-0,96
-R

C02
COi

4+

-A2

CO1

(02_

C02

(Oj

Uc

UiL

50V

,1

M
286

287


Botr^klcn

thiJrc

V^t l i LTDH

t r c n k€nh

VTV2.

t^p

2 - Chu

VMn

Bicn

Cau 5: Dong dien xoay chieu qua mot doan mach c6 bieu thuc i = Iocos(1007tt 7r/3) ( A ) (t do bang giay). Thoi diem thu 2010 gia trj tuyet doi ciia cuong do
dong dien tiVc thoi bang cuong do dong dien hieu dung la
A . t = 12043/12000(5).
B . t = 9649/1200 (s).
C. t = 2411/240 (s).
D . t = l/48(s).
Humigdait
*(0)

=

IOOTT.O--

3.

^ ^H)5,

^<^^''-

= — => Chuyen theo chieu dUcfng.

au 7: Dat mot dien ap u = 50 %/2 coslOOTtt (V), (t do bSng giay) vao hai dau

doan mach noi tiep gom dien tro R = 30 Q, tu dien va cuon day. Biet dien ap
hieu dung tren tu la 80 V tren cuon day la 10V26 V va tren dien tro R la
30 V. Cong sua't tieu thu dien cua doan mach la
A. 20 W.
B. 30 W.
•i
C. 50 W.
D. 40 W.
Huong dan

-

U,d =

1 =

V2

>/uf+uF = 1 0 7 2 6

V

U L = 5 0

*

^

. :* •:
•

:

50^ =

h.%..::^.\c
^'^ "^Jb

r =^
I

J^G

P =

Ldn 4 ; t4 = 13T T T _ 19T
24 ^ 8 ^ 8 ~ 24
Ldn 2010 = 4. 502 + 4: tjoio = 502T + 1^02

I = Hii

R

.

= lA^'"'^"'

10

r ( r + R) = 40(W)

A A F B : A B ^ = A F ^ + FB^

7T 12055T 2411, ,
: 502T + — =
=
(s)
24
24
240

EB = EF - EB = 8 0 -

2 5 0 0 = ( 3 0 + x)^ + [ 8 0 - V 2 6 O O

\^600^

-

x=

10

P = l2(r + R) = I ( I r + IR) = ^ ( U r + U R ) - — ( 1 0 + 30) = 40(W)
R

MAU ....

\^2)
A

0,51„

=

+ 30^ + 60.Ur + 80^ - 160.Ui^

A N E B ; BE = V N B ^ - N E ^ = 7 2 6 0 0 ^

11=502

1

+ lil

oi;

u,=io . , .

U2=(UK+U,f+(UL-Ucf
'V

-

Uc = 80 V

; imA :.< * ' :

Ldn i .• t T

24
T
T T 7T
Lan J : ty = — + — + — = —
24 8 8 24
7T T T
13T
Ld?i 3:U =
24 ^ 8 ^ 8

•' '

C

M

Lr

\

ijja

\i TM

1

\

\

( 4 ) \
^d)„„ = - 7t/3
Cau 6: Dat dien ap xoay chieu c6 gia tri hieu dung 120V tan so 69Hz vao hai

Cau 8: Dat dien ap xoay chieu on dinh vao hai dau doan mach gom cuon day

dau mot bong den huynh quang. Biet den chi sang len khi dien ap dat vao

noi tiep voi tu dien co dien dung C thay doi. Khi C = C i dong dien trong

den khong nho han 60V2V. Thoi gian den sang trong moi giay la:

mach la i i va cong sua't tieu thu cua mach la P i . Khi C = C2 < C i thi dong

A.l/2(s)

dien trong mach la i2 va cong sua't tieu thu la P2. Biet P2 = (7 - 4 ^/3 ) P i va i i

B. l/3(s)

C.2/3(s)

D. 0,8 (s)

vuong pha voi i2. Xac djnh goc lech pha (pi va (p2 giua di^n ap hai dau doan

Huang dan

288

Thdi gian hoat dong trong mot giay chu hi la:

\

1
b
1
6072
2, ,
t = t.4.—arccos
= 60.4.
arccos
^ = -(s)
CO
Uo
1207t
120V2
3^ ^

^

mach vol i i va i2.
A . (pi = 71/12 va (p2 = -57r/12.

B. (pi = -71/6 va 92 = n/3.

C . (pi =-7t/3 va(p2 = 7i/6.

D. (pi = - n / 4

r

va (p2 = 7i/4.

-89