bổ trợ kiến thức vật lí phần 2 điện xoay chiều chu văn biên

T
" ^—
5 A^T"
CHU
VAN BIEN
Gi^o vien
chuong
trinh
bo
tro Itien
thurc
V$t
li
12,
kenh yffZ
-
Dai
Truy^n hinh Viet
Nam
Bo tra
hion
IMi
«ii
LUYEN
m
DAI
HOC
IKEN
KENHWi
PHAN
LOAI

VA
fHUONG
PHAP
GlAl
CAC BAI TOAN
CO
BAN, DIEN HINH, HAY, LA VA KHO.
Phan
i!: Dltn HOW CHIEU
•
Danh
cho
ttn
sinh
lOp
12
On tap va
thi
Bai hqc,
Cao
dang.
V'
0
Blen
scan
theo nOl
dung
va
cau
tnic

6&
tN
ciia BO
GD
E
DT,
1 ,
HA HOI
NHA
XUAT
BAN DAI HOC
QUOC
GIA HA NQI
Chude
1.
MACH DIEN
BAI TOAN LIEN QUAN DEN MACH CHI
CO R,
CHI
CO L,
CHI
CO C 3
BAI TOAN LIEN QUAN DEN
THCJl
GIAN
12
BAI TOAN LIEN QUAN DEN DIEN
LLfONG
19
BAI TOAN LIEN QUAN DEN MACH

RLC
NOI
TIEP
23
BAI TOAN LIEN QUAN DEN BIEU DIEN
PHLfC 37
BAI TOAN LIEN QUAN DEN CONG
HUCJNG
DIEN
VA DIEU KIEN LECH PHA
47
BAI TOAN LIEN QUAN DEN CONG
SUAT
vA HE SO
CONG
SUAT
58
BAI TOAN LIEN QUAN DEN GIAN
DO
VECTO
71
BAI TOAN LIEN QUAN DEN THAY DOI CAU
TRUC
MACH,
HOP
KIN,
GlA TRI TL/C THCfl
104
BAI TOAN LIEN QUAN DEN
ClJC

TRI 132
Chude2.
::
1:
MAY DIEN
BAI TOAN LIEN QUAN DEN MAY PHAT DIEN
XOAY
CHIEU
1
PHA
200
BAI TOAN LIEN QUAN DEN MAY PHAT DIEN
XOAY
CHIEU
3
PHA
211
BAI TOAN LIEN QUAN DEN DONG
CO
DIEN
215
BAI TOAN LIEN QUAN DEN MAY BIEN
AP 225
BAI TOAN LIEN QUAN DEN TUYEN TAI DIEN
237
BAI
TAP
DINH
TINH
253

,
, 286
BAI
TAP
DINH
LUONG
^,„rn: :v;.r.r::.::;:::.T;::::.:^^^
Cty
TNHH
mv DWH
Khang
Vipt
Chu
ae 1.
MACH DI^N
BAI
TOAN
LIEN
QUAN
DEN
MACH
CHI
C6
R, CHJ
C6
L, CHJ
C6
C
Phuong
phdp

giai
1)
Quan
he gia tri
hieu
dung
Mach
chi c6 R
thi
u va i
cung
pha va R = ^ = ~ "
•
••'
''^v^ 'f v
• 1 II; '
•
••
' ,
Mach
chi c6 L
thi
u som han i la
Mach
chi c6 C
thi
u tre hon i la — va
Z^-
=
Doi voi

mach
chi c6 L, C
thi
u
viiong
pha
vdi
i nen
i
= (oL =
Uo
lo
1
Uo
(oC
lo
In
2
/ A2
u
U„
Vi
du 1: Dat vao hai dau mot
cuon
cam
thuan
L
mot
dien
ap

xoay
chieu
c6 gia
tri
hieu
dung
U
khong
doi
va tan so f
thay
doi. Khi
f = 60 Hz
thi
cuong
do
hieu
dung
qua L la 2,4 A. De
cuong
do
hieu
dung
qua L
bang
3,6 A
thi
tan
so CLia
dong

dien
phai
bang
MI- v '
A.
75
Hz.
. B.
40Hz.
C. 25
Hz.
D.
50V2Hz.
Ir
1
=
U
_ U
I,
=•
I.
=
^""^'^
^
f2
= f, .1L = 60.^ = 40
(Hz) =>
Chon
B.
U

I2 3,6
27:f7L
"If'a'l
0'.'
IV^
Vi
du 2:
Mot
tu
dien
khi
mac vao
nguon
u = uV2
cos(100Kt
+
7t)
(V)
thi
cuong
do
hieu
dung
qua
mach
la
2A. Neu
mac tu vao
nguon
u =

Ucos(1207tt
+ 0,5::)
(V) thi
cuong
do
hieu
dung
qua
mach
la bao
nhieu?
A.
1,2N/2A.
B. 1,2A. ' C. V2 A. D. 3,5 A.
""'XHuongdan
••*'-,''-:''>:^'<':':<-'y
.z,:^''-:'''-<':•'''••'
I
=
-^
=
coC.U^j;'="'^y;
=.k = ^^I,=l,2V2(A)=>ChonA.
Zc
[l2=(02CU2
Ij (0|U,
Vi
du 3:
Doan
mach

dien
xoay
chieu
tan so fi = 60 Hz chi c6 mot tu
dien.
Neu
tan
so la h
thi
dung
khang
cua tu
dien
tang
them
20%. Tan so
A.
f2 = 72
Hz.
B. f2 =
50
Hz.
C. f2 = 10
Hz.
D. f2 = 250
Hz.
BS
trg
kiSn
thiic V$t If

LTBH
trBn
kenh VTV2. t^p 2 - Chu V^n
Bi&n
Huong
dan
-?C2.
^ A. = 100% + 20% = 1,2 => f2 = = 50(Hz) Chon B.
ZQI
(2 1,2
Chuy:
1)
Dien dung cm tu dien vhdng tinh
theo
cong thiec: C = ^
9.10
.47rd
,,
moi, d la khodng each giua hai ban tu va S la dien tich doi dien gifm cdc ban tu).
1)
Khi chat dien moi trong tu la ichong khi thi ZQ = 1
S
nen = ^ va cwong do hieu dung
chay
9,10 .4jid
qua tu I =
_U_
=
COCQU
.

(s
Id hang so dien
Neii nhung cdc bdn tu ngdp vao trong dien moi long (c6 hang so dien moi s) va cdc
=
ZCQ
nen cuang do hieu
yeu tokhdc khong doi thi dien dung cua tu C = ^—
1
' 9.10 And
dung
qua tula I' =
coCU
=
EI
.
New nhiing x phan tram dien tich cdc bdn tu ngdp vao trong dien moi long (c6 hang
so dien moi s) vd cdc yeu tokhdc khong doi thi bo tu C gom hai tu Ci, Ci
ghep
song
(l-x)S
„ EXS
song: Ci = •
•
= (l-x)Co, C2=-
• =
ExCn
9.10\47td
9.10^47id
^ C = + C2 = (1 - X +
ex)Co

. ' . .'.,1'n<<'-ti
Cwang
do hieu dung qua mqch h'lc nay Id V =
coCU
= (1 - x +
8x)I.
Neu
ghep
sdt vdo mot bdn tu mot td'm dien moi c6
hang so dien moi sco be day bang x phan tram be'
day cua lop khong khi vd cdc yeu tokhdc khong
dot thi bo tu C gom hai tu Ci, Ci
ghep
noi tiep:
Cn
=>
c
=
9.10\47r(l-x)d (1-x)
C,C,
E
ES
9.10
.47rxd
-X
S
1
X
M
-1^2

: +
E(1-X)
Co-
Cwang
do hieu dung qua mqch luc nay Id ]' =
uCU
=
•
-I.
X
+
E(1
- x)
Vi
du 4: Mot tu dien phang khong khi
dugc
noi vao nguon dien
xoay
chieu thi
cirong do hieu dung qua mach la 5,4 A. Neu
nhiing
hai phan ba dien
tich
cac ban tu ngap vao trong dien moi long (c6 hang so dien moi e = 2) va cac
yeu to khac khong doi thi
cuong
do hieu dung qua tu la
A.
7,2 A. B. 8,1A. C. 10,8 A. D. 9,0 A.
Cty TNHHITTVDVVHKhang VIft

Huang
dan
Cn=-
9.10^ .47rd
C,
=
•'1/
••••
' 9.10^.47td 3
C, =
=^Zr =
9.]0^47rd
5
3'
-^l^^C
=
Ci+C2=-C
0
^co
3::^
I = = ^.5,4 =
9,0(A)
Chon D.
3
5
3 , • „;;,,v v,^f .
Vi
du 5: Mot tu dien phang khong khi c6 hai ban
song song
each

nhau mot
khoang d
duoc
noi vao nguon dien
xoay
chieu thi cuang do hieu dung qua
mach la 6,8 A. Dat vao trong tu dien va sat vao mot ban tu mot tam dien
moi
day 0,3d c6 hang so dien moi e = 2 thi
cuong
do hieu dung qua tu la
A.
2,7 A. B.8,0A. C. 10,8 A. D. 7,2 A. .
Huang
dan y
S
>KOO [ATO-U
- u u'.;
S _
lOCo
-•U
'ijl'
s
"
9.10'^.47:d
9.10\47i.0,7d 7
CintC2
Q.C2 ^20^
c g.s _
20C0

^ 9.10^.47i.0,3.d 3
Ci+C,
17
.a
=>Zr
=
20
17
1
=
^.1,,
=^.6,8
= 8(A)
r:^
Chon B.
2) Quan he gia tri tuc thoi {A.}S
1)'-'
Mach chi c6 R thi u va i ciing pha nen R = — = = 'T
•
'
T.
Mach chi c6 L thi u som pha hon i la n/2 nen ZL = coL = —- = —^ ^ ^ ,,.
'I
In
i
=
IQ
COS
cot
u

= UQ
COS
cot + —
2,
= -UQ
sin cot
2
2
1
u
=
1<
+
=
1<
Jo;
=
1<
Un
= U72
- : 1 u Uo u
Mach chi c6 C thi u tre pha hon i la n/2 nen = — = — = — ^ —
COC
I In
i
=
I()
cos cot
u
= U() cos cot

2y
=
U() sin cot
2
2
1
u
=
1<
—
+
=
1<
Do'i
vc^i mach chi c6 L, C thi u vuong pha voi i nen
Uo
= uV2|:;-
=
1
2
1
U
+
luoj
Ba
trg
kiSn thurc
V^t li
LTDtl tren
henh

VtV2.
t^p 2 - Chu Vdn
Bien
:i=0<=>u
= ±U
(Do thi quan he
ii,
i la duong clip).
[u
= 0 <=> i = ±I()
Vi
du 1:
(DH-20n)
Dat dien ap u =
uV2cosa)t
vao hai dau mot tu dien
tiii
cuang
do dong dien qua no c6 gia tri hieu dung la I. Tai thoi diem t, dien ap
a hai dau tu dien la u va cuong do dong dien qua no la i. He thuc lien he
giua cac dai luong la
, U^ i^ 1 ^ U^ i^ ' _ U^ i^ , ^ u2 i2 1
A.
-^ + -T- = B. —^ + -^ = 1. C. —5- + -:5- = 2. D. ^ + -5- =
T2 T2 A U2 J2 ^2 j2 y2 j2 2
u
= U\/2
coscot
Huattg
dan

— = %/2
coscot
U
i=lN/2
cos
0)t
= -I\/2
sincot
J =
-N/2
sincot
2 -2
+ V = 2 ^
Chen
C.
Vi
du 2: Dat vao hai dau doan mcich chi c6 cuon cam thuan mot dien ap
xoay
chieu u = UdCOslOOTit (V).
Biet
gia trj dien ap va cuong do dong dien tai thai
diei-n
t^ la u^ =50^ (V), -Jl (A) va tai thoi diem t2 la U2 = 50 (V),
i2 =-^/3 (A). Gia tri Un la >
A.50V. B.IOOV.
C50V3V.
D. IOOV2 V.
! j,
Huang
dan

2
2.2500
_ ^
fUo=100(V)
^0 ^0
3
2500
,
+ —=^ = 1
I
—Chen
B.
.y ,,
,
,„
I„=2(A)
•
tii'VidnmpiS
Vi
du 3: Dat vao hai dau mot cuon cam thuan c6 do tu cam
0,3/;:
(H) mot dien
ap
xoay
chieu.
Biet
dien ap c6 gia trj tuc thai
60-J6
(V) thi dong dien c6 gia
trj

tuc thoi V2 (A) va khi dien ap c6 gia tri tuc thai
60>/2
(V) thi dong dien
CO
gia tri tuc thoi %/6 (A). Hay
tinh
tan so cua dong dien.
A.
120 (Hz).
44-
B. 50(Hz). C. 100 (Hz). D. 60 (Hz).
' ' • '
Huang
dan
360.6
= 1
6
360.2
,
— + —^ = 1
Uo =
120V2
Io-2^/2
U
U,
=:>
ZL =
2nfL
= = 60 ^ f = lOO(Hz) => Chon C.
In

Chu y: Hop kin X chi
chi'ra
mot
trong
3
phan
tit la R
hoac
C
hoac
L. Dat vao hai dau
hop X mot
dien
dp
xoay
chieu
thi
dien
dp
tren
X va
ddng
dien
trong
much
a
thai
diem
t|
CO

gia tri Ian
luvt
Id ij, u^ vd a
thai
diem
t2
W
i2, U2 . , ,„ ,
Neil
^ = ^^a thiX = R = a.
*
Nguvc
Igi
nujch
chi c6 L
hoac
C.
(Dexdc
dinh
dwgc
L
iiay
C thi nen Iwu y: Neu f
tang
thi Zi
tdng
nen I
gidm
con
ZQ

gidm
nen I
tang).
Vi
du 4: Mot hop X chi
chua
mot trong 3 phan tu la dien tro thuan
hoac
tu dien
hoac
cuon cam thuan. Dat vao hai dau hop X mot dien ap
xoay
chieu chi c6
tan so f thay doi. Khi f = 50 Hz thi dien ap tren X va dong dien trong
mach
6
thoi
diem ti c6 gia trj Ian lugt la: ij = lA, Uj = 100 V, 6 thai diem t2 thi:
i,= A, U2 = lOOV. Khi f = lOOHz thi
cuang
dp dong dien hieu dung
trong
mach
la 0,5 V2 A. Hop X
chua
A.
dien tro thuan R = 100 Q. ' '"
B. cuon cam thuan c6 do tu cam
I/TT
(H)

C. tu dien c6 dien dung C =
IO-VTI
(F).
D.
tu dien c6 dien dung C = 100 ^3
/TI
(F). C
Huong
dan
•2
r 1
-^nnan
fUo=200
"""lo
=2=>I
= V2(A)
on
4+4=1
i.4=i
Jl_
30000
10000
= 1
(I
I
Wf^ t
Khi
tan so tang gap doi neu la tu thi dung khang giam 2 Ian nen dong hieu
dung
tang 2 Ian, tuc la F = 21 = 2 V2 A. Nhung

theo
bai ra F = 0,5 V2 A = 1/2
nen X = L sao cho: i'" imi
Z,
=2niL
=
-
Uo _ 200
50 ^0 2 7t
L
= i(H)=>ChonB.
Vi
du 5:
(DH-2010)
Dat
di§n
ap u =
Uocoscot
vao hai dau cuon cam thuan c6 do
tu
cam L thi
cuang
do dong dien qua cuon cam la
A.
i =
HLcos
coL
C.i = -^
coL
cos

n
a)t + —
2.
n
(ot
2
B. i =
D.
i =
(OLN/2
cos
7t
a)t + —
2.
CO
LV2
cos
7t
cot
2J.
Huang
dan
Vi
mach
chi c6 L thi i tre pha hon u la n/2 nen
Bo
trfi
kien
thijrc
V,jt li

I.
roil iren
kcnh
VTV2.
t^p 2 - Chu V^n
Blen
1
=
—^cos
cot
2
coL
-cos
2
•Chon
C.
Vi
du 6: Dat
dien
ap u = Uocos(1207Tt -
TT/4)
(V) vao hai dau mgt tu
dien thi
von
kenhiet
(c6
dien
tro rat
Ion)
mac

song song
voi
tu
dien
chi 120^/2 (V),
ampe
kenhiet
(c6
dien
tro
bang
0) mac noi
tiep
voi tu
dien
chi 2
(A).
Chon
ket
luan
diing.
,i'
A.
Dien dung ciia
tu
dien
la l/{7,2n) (mF), pha ban dau
ciia dong dien
qua
tu

dien
la n/4.
J
B.
Dung khang
cua tu
dien
la 60 Q, pha ban dau
ciia dong dien
qua tu
dien
n'; la = 71/2. .vh r
nM'. Wvrl
C. Dong dien
tuc
thai
qua tu
dien
la i = 4cos(1007it +
7i/4) (A).
D.
Dien
ap cue dai
giira
hai dau tu
dien
la
120 y/l (V), dong dien
cue
dai

qua
tu
dien
la 2
V2
(A).
Huong dan
Dien dung tu
duoc
xac
dinh
tir
=
— =
<=>
-
^
" ^ coC IA 1207rC
Vi
mach
chi c6 C
thi
i som pha hon u la n/2 nen
i
= I>/2cos 1207tt + - =4cos
1
I20V2
2V2
=i.C=
1207rt-^

+ ^
4 2
120Trt + -
7,271
(F)
•
Chon
A.
hi,;
Vi
du 7: Do thj
bieu dien cuong
do tuc
thoi
cua
dong dien
xoay
chieu
chi c6
cuon
cam
thuan
c6 cam
khang
ZL
= 50 Q o
hinh
ve ben.
Viet bieu thue dien
ap

tuc
thoi
giira
hai dau
cuon
cam. ' " :
i
(A)
A.
u = 60cos(507it/3 +
7t/3) (A).
B. u = 60sin(1007rt/3 + n/3)
(A),
C.
u = 60eos(507it/3 + n/6)
(A).
D.
u = 30cos(507rt/3 +
Tt/3) (A).
Huong dan
i
=
IQ
cos (cot +
cp)
= 1,2 cos (cot +
cp)(A)
Liicdau,i
= — ycidang.dive i =
0nernp

=
—
2. 3
Thdi
gian ngdn nhdt
ditii
i = — den i = Old — = = 0,01
2
12 12co
5071
•
\%
-n,.:,,
, • \
T
27t
Vi
mach
chi eo L
thi
u som pha han i la
7t/2
nen
507rt
71 71
507Ct 571
Chu
y:
Mach
^om L ndi tiep voi C thi dien dp giim hai dau

doqn
mach
u =
ui,
+ uc
V01
Uc
Vi
du 8: Mot
doan
mach
mSc noi
tiep
gom: tu
dien
eo
dung khang
Zc va
cuon
cam thuan
c6 cam
khang
Zi,
=
0,5Zc. Dien
ap
giira
hai dau tu:
uc = 100eos(1007it +
7t/6)

V.
Dien
ap
giiia
hai dau
doan
mach
la:
A.
u = 200eos(1007it -
57t/6)
V. • •' B. u = 200cos(100Txt -
7r/3)
V.
C.u
= 100eos(1007it-571/6) V. D. u = 50cos(1007it +
7:/6)
V.
Huong dan ,
1+:
• |«~
:fUSU.:dt'
•
Up
Dien
ap
giij'a
hai dau
doan
mach:

u =
UL
+ =
ZL
+
u^
u
= -0,5uc +
Uc
=
0,5uc
= 50 cos
1007Ct
+
-
6,
(V)=>ChonD.
jji ,:v
Chu
y:
1) NcU
cho
•
thi
du'a
vao he
thi'fc
\
(dm) in:t)\i
^n;.iC)

.!'-<i,:,)
en
npiu
u\p iBsi oi\'> UM
= 1-
Thay
UQ^IQZL
hoac
Uo=IoZc
Mach
chi
c6
C thi i sdm pha
hcfn
u Id K/2.
Mach
chi
c6
L thi i tre pha
hcfn
u Id n/2.
/.I
2)
Neil cho
ii;i2
ui;u2
••1
thi dim vao 2 he thuc
(I
44-

T2 TT2
Mack chi c6 C thi i sdm pha hcfn u la
TZ
12 vd
ZQ
=
Uo=?
J__Uo
Mach
chi coLthii tri pha hem
uldn/2vdZi=(dL
=
coC IQ
co
=
?.
In
•
CO
= ?.
Vi
du 9: (DH-2009) Dat
dien
ap u = Uocos(1007rt -
7t/3)
(V) vao hai dau mot tu
dien
CO
dien dung 0,2/7t
(mF). 6

thoi
diem dien
ap
giua
hai dau tu
dien
la
150 V thi
cuong
do
dong dien trong
mach
la 4 A.
Bieu
thuc ciia cuong
do
dong dien trong
mach
la
A.
i = 4
>/2
cos(1007rt +
7r/6) (A).
B. i = 5cos(1007rt +
7t/6) (A).
C.
i = 5cos(1007tt -
7r/6) (A).
D. i = 4

V2
cos(1007rt -
7t/6) (A).
h/.'AM.ii'^y'AH
Huongdan
);|^:Kr;i;flj!p*iJ,r.):^i;^»;.fi!a
,.
Cdch
1:
Gidi
tuan tu:
iriJ'rrs!
hamh.
it'jil: ••.!,!'•
1
1 : : :
Bo
trfl kicn Ihitc
V^t li
LTDH tren hcnii
VTV2,
t^p 2 - Chu Vdn
Bicn
u
=
IQZC COS
lOOTlt
3
i
=

IQ
cos
3 2
\
/
u
=> COS
lOOTlt-
u
/ \
3.
IQZC
\
(
-i
sin
lOOTTt-
J
V
3y
1
=
u
2
+
-1
2
2
+
2

+
[1,50
J
2
+
=> In = 5A => i =
5cos
1007:t
+ -
Cdch
2:
Gidi
nhanh
(van tat):
Dua vao he thuc:
-4r
+
= 1-
Thny
U() =
loZc
150
In
.50
^2
-4
.I„=5(A)
Vi
mcich chi c6 C thi i som pha hem u la TI/2 nen
i

=
5cos
100Ttt
+ -
6
(A):^Chon B.
Vi
du 10: Dat vao hai dau tu dien c6 dien dung
1/{3n)
(mF) mot dien ap
xoay
chieu.
Biet
dien ap c6 gia tri tiic thoi 60^6 (V) thi dong dien c6 gia tri tuc
thoi
yfl (A) va khi dien ap c6 gia tri tuc thai SOs/l (V) thi dong dien c6 gia
tri
tuc thoi -^6 (A). Ban dau dong dien tuc thoi
bang
gia tri cue dai, bieu
thii'c
CLia
dong dien la
A.
i =
2^y3cos(^007tt
+ 7t/2) (A). B. i = 2 V2
coslOOTtt
(A).
C. i =

2V2cos507it(A).
D. i = 2 ^/3
cos(507it
+ 7r/2)(A). ,
Huong
dan
4
2
360.6
,
6
360.2 ,
Uo=120V2
1
Up
coC I„
•
CO =
50TC
rad
Vi
ban dau dong dien tiic thoi
bang
gia trj eye dai, bieu thiic ciia dong dien
CO
dang i = I,, cos cot thay so vao ta
dugc
i = 2V2
COSSOTTI
(A) => Clion C.

Vi
du 11: Dat vao hai ban tu dien c6 dien dung
100/(37r)
(|aF) mot dien ap
xoay
chieu u =
Uiicos(1007it
+ (pu) (V) thi dong dien qua tu c6 bieu thuc
i
= 2V2
cos{1007tt
+ 7x/3) (A).
1) Tinh dien ap giiia hai ban tu tai thoi diem t = 5 (ms).
t
•
2) Xac dinh cac thai diem de dien ap u = 600 (V). » I ',/
3) Xac djnh thoi diem Ian thu 2014 de u = -300 V2 (V).
4) Xac djnh thoi diem ian thu 2014 de
|u|
= 300 V2 (V).
Huang
dan
1) Tinh dung Ichang: Zc= — =
300(Q).
coC
Cty
Tnnn
MTV
DVVH
Kliang Vift

Vi
mach
chi c6 tu dien nen dien ap tre pha hon dong dien la n/l:
u
=
IQZ,^
cos
3 2
=
600V2cos[
lOOTit |(V).
V
6 j
u,
_3^
=600V2cosfl007t.5.10''"^ l
=
300V6(V).
^5.10 • I 6y
2)
Giai phuong
trinh:
u = 600 (V) => cos
lOOTtt
^/2
lOOKt
6
lOOTit
6,
=

-+k.27T
4
=
+ 1.271
4
1
+A(s)(k
=
0/1,2 )
t =
240 50
1
1200 50
+ — (s)(l =
1,2,3 )
3) Ta thay:
2014
= 1006 du 2 => t =
1006T
+1,.
De
tinh
t2 ta c6 the dung vong tron lugng
giac:
2K
(t>,
- On
CO
+
271-

10071
200
(s)
t
=
1006.0,02
+ — =
20,135
(s)
200 ' ^ >
4) Ta thay:
2014
= 503
du:
2 => t =
503T
+ tj .
De
tinh
t2 ta c6 the dung vong tron luong
giac:
27t
t,
=
O, - On
_ ^2
1
(s) =>t =
503.0,02
+

1
6041
CO
lOOTt 120' ' • 120 600
CM
y: Vi v6i
mach
chi
chiia
L
hoqc
C thi u va i
vuong
pha
nhau
nen
thuang
c6 bai
loan
cho
dien
ap
(dong
dien)
a
thai
diem
nay tim
dong
dim

(dien
dp) a
thai
diem
triivc do
hoqc
sail
do mot
khoang
thai
gian
(vuong
pha) At = (2n + l)T/4:
U2
Vi
d\ 12: Dat vao hai dau doan
mach
chi c6 cuon cam thuan c6 do tu cam
0,4/7t
(H) mot dien ap
xoay
chieu u =
UocoslOOTct
(V). Neu tai thai diem ti dien
ap la 60 (V) thi cuong do dong dien tai thoi diem ti +
0,035
(s) c6 do Ion la
A.
1,5 A. B. 1,25 A. C. 1,5 V3 A. D. 2 V2 A.
BS

tr^
kieti
thUc
V^t
II
LTDlt
tteti
k&nh
VTV2.
t$p 2 - Chu VSn
Bi&n
Huong
dan
71
Cam khang Z, =wL =
40(Q).
Vi t2
=0,035
= — la hai thoi diem vuong
pha nen:
60
40
= l,5(A)=>Chon A. r-iT- /c',,;
Vi
du 13: Dat vao hai dau doan
mach
chi c6 tu dien c6 dien dung
0,l/7i
(mF)
mot dien ap

xoay
chieu u =
UocoslOOnt
(V). Neu tai thai diem ti dien ap la
50 (V) thi cuong do dong dien tai thai diem ti +
0,005
(s) la: . i
A 0,5
A. B. 0,5A. C. 1,5 A. .
D 1,5A.
Huong
dan
z, =•
(oC
=
100Q;u
= Uo
cosl00Tit=i>
U(f^j
=
U,,
coslOOTtti =50
1
= cos
,
'(t]+0,005)
1007rt
+ -
2.
•(ti+0,005)

-
COS
1007i(ti+0,005)-
°
^-
=
-0,5(A)
=>Chon A.
;„•••
lift:
100
;0
filsJ
rfniiiaO,
BAITOAN
LIEN
QUAN
DEN
THOfI
GIAN
Phuangphdpgidi
r' i;*, ' ' * •
1) Thai
gian
thiet
bi
hoat
dong.
p , , (|„.,
Mot

thiet bj dien
duoc
dat duai dien ap
xoay
chieu u =
Uocoscot
(V). Thiet bi
chi
hoat
dong khi dien ap tuc thai c6 gia tri khong nho hon b. Vay thiet bj
chi
hoat
dong khi u nam ngoai khoang (-b, b) (xem hinh ve)
1 b
Thai gian
hoat
dong trong mot nua chu ki: 2t, = 2.
—arccos-—-
,>|' ,|
r
" ^0 '
Thai gian
hoat
dong trong mot chu ki: t^ = 41, =
4.—arccos—
''''"^
Thoi
gian
hoat
dong

trong
1 s: ft^ =
f.4.—arccos
—
CO
U(,
HtU „ ,. . 1 b
. Thai
gian
hoat
dong
trong
t s: thj =
t.f.4.—arccos—
CO
Un
—T
1 ~ T ' ! '—*
t (s)
arccosi
arcsin^
arcsin^
arccosS-
j
O
1 b
—
arccos
—
1 b

—arccos
—
Cty
Train
MIV
U VVH
Khang
Vlft
Vi
du 1: Dat dien ap
xoay
chieu c6 trj hieu dung 120 V tan
so'60
Hz vao hai
dau mot bong den huynh quang.
Bie't
den chi
sang
len khi dien ap dat vao
den khong nho hon 60 N/2 V. Thoi gian den
sang
trong moi giay la:
A.
l/2(s).
B.
l/3(s).
C.2/3(s).
• D. 0,8 (s).
Huong
dan

Thoi gian
hoat
dong trong 1 s:
1
b 1
60V2
2/;^"^t!::'''';:''^^'^'''^^
t
= f.4.
—arccos
= 60.4.
arccos
7= = —(s) =>
Lnon
L.
CO
U,) 12071
120V2
3'
'
Vi
du 2: Mc)t den ong su dung dien ap
xoay
chieu c6 gia trj hieu dung
220V.
Bie't
den
sang
khi dien ap dat vao den khong nho hon 155 V. Ty so giCra
khoang thai gian den

sang
va khoang thoi gian den tat trong mot chu ky la
A.
0,5 Ian. B. 2 Ian. C. ^ Ian. D. 3 Ian.
Huang
dan
Thoi gian den
sang
trong mot chu ki: v • ,:, ' ;'
. . ^ b T 155
t,
=
4.—arccos
=
4.—arccos-
2T
CO
2n
220V2
T t-
Thoi gian den tat trong mot chu ki: t, = T -
tj^
= — => — = 2
=>
Chgn
B.
tt
2) Thai
diem
de

dong
dien
hoac
dien ap
nhan
mot gia tri
nhat
dinh
De xac dinh cac thoi diem c6 the dung giai phuong
trinh
luong
giac
hoac
dijng
vong tron luong
giac.
Vi
du 1:
(DH-2007)
Dong dien
chay
qua mot doan
mach
c6 bieu thuc i =
losinlOOTit. Trong khoang thai gian tCf 0 den 0,01 ? cuong do dong dien tiic
thai
CO
gia tri
bang
0,5Io

vao nhung
thai
diem • j.
A.
1/300 sva 2/300
s ?.
C. 1/500 s va
3/500
s.
B. 1/400 sva
2/400
s.
I
D. 1/600 va
5/600
s.
Huang
dan
Khi
bai toan chi yeu cau tim hai thai diem dau c6 the giai phuang
trinh
cot +
cp
= a + (271)
o,t +
(p
=
7r-a
+ (27i) ^P^^fk^''^
cot +

(p
= a + (2?:) „: .,
ojt+ 9 =-a+ (27t)
luong
giac:
sin (cot + cp) =
sina
=
cos(o)t
+ cp) =
cc«a
:
(Neu tim ra t < 0 moi
cong
2?:).
i
= Iosinl007it = ^
1007rt
= -:
6
t
=
1
1007tt
= —=>t =
600
5
600
(s)
=> Chon D.

-(s) ^J^''
13
B6 trff kiSn thCrc
V^t
liLTBtl trSn kSnh
VTV2.
t^p
2
- Chu
VSn Bien
Vi
du 2: Dien ap hai dau doan mach c6 bieu thiVc u =
200cos(1
OOTit
+
57r/6)
(u
do bang von, t do bang giay). Trong i<hoang
thoi
gian tu 0 den 0,01 s dien
ap tiVc
thoi
CO gia trj bang 100 V vao nhung
thoi
diem , i v
A.
3/200
s va
5/600
s.

\f|s^,,i;,:,
B. 1/400 s va
2/400
s.
C. 1/500 sva
3/500
s. ' ' ' ' D. 1/200 va
7/600
s.
Huong
dan
Cdch
1: Gidi
phumig
trinh
luong
gidc
u
= 100=^ cos
lOOTTt
57:
=> Chon A. (Neu khong cong them 2n
Cdch
2:
Dung
vdng
iron
luang
gidc
1007rt

+ —= - + 2T:^t = —(s)
6 3 200
1007rt
+ —= +
27i=>t
= —(s) A
6 3 600^ ^ '
1007rt
+ —= -=^t = -
—(s)<0
6 3 200
1
OOTTt
+ — = ^ t = -—(s) < 0
6 3 600
Vj
tri xuat phat ung vol pha dao dong: 0„ = —
6
Lan
1 dien ap tuc
thoi
c6 gia trj bang
100 V ung voi pha dao dong:
= ^
+ 2Tt nen
thoi
gian:
71 „ 5T:
-
-

+ 271 -
-
-
3 6
0) 10071 600
Lan
2 dien ap tuc
thoi
c6 gia tri bang 100 V ung vol pha dao dong:
TT
<I>2
= — +
27T
nen
thoi
gian: t2 =
3
71 57r
^2-Oo
3^^^"T
w
10071 200
Vi
du 3: Dien ap giCra hai dau mot doan mach c6 bieu thuc: u =
120sin]007rt
(u
do bang von, t do bang giay). Hay xnc djnh cac thai diem ma dien ap
u
= 60 V va dang tang (voi k = 0,1,
2, ).

A.
t= J/3 + k(ms).
C. t = l/3 + 20k (ms).
B. t = l/6 + k(ms).
D.
t = 5/3 + 20k (ms).
'*
Hicangdan
. ,
71
. . ' ' hihm^:r>:
u
=
120sinl007tt
= 60
, inn . „
=> 1
OOTlt
= — +
k27t
u
=
1007i.l20cosl007rt>0
6
1
2
=>t
= + k (s) =
600 100
1

, 2 ^
-
+ k
1600 100
J
.10' (ms) = - +
20.k(ms)
=> Chon D.
3
Cty
Timti nrv
DVVH
Khang
Vipt
Vi
du 4: Dien ap giua hai dau mot doan mach ccS bieu thuc u =
U()COS(2TTt/T).
Tinh
tu thai diem t = 0 s, thi
thoi
diem lan thu 2014 ma u =
0,5Uo
va dang
tang la '•
,-\y-''''
.] r ''
A.
12089.T/6.
B.
12055.T/6.

C.
12059.T/6.
D.
12083.T/6.
Huotig
dan
Cac thai diem ma u =
0,5Uo
va dang tang thi chuyen dong
tron
deu nam o
nua
duoi
vong
tron
krong
giac
(moi chu ki chi c6 mot lan).
Vi
tri xuat phat ung voi pha dao dong: O,, = 0
Lan
1 ma u =
0,5U(i
va dang tang ung voi pha dao dong:
Oj =-^ + 271 nen thai gian: , , ;
tl
=•
cl>i -O
+
271-0

3 _5T
0)
271
T'
Lan
2: t2 = t, +T,
Lan
2014: 12014 =ti
+2013T
5T
2014
+ 20131 =
12083T
•
ChonU.
6 6
Vi
du 5: Dien ap giua hai dau mot doan mach c6 bieu thuc u = Uocos(2Tit/T).
Ti'nh
tu
thoi
diem t = 0 s, thi
thoi
diem lan thu 2010 ma u =
0,5U()
va dang
giam
la
A.6031.T/6.
B.12055.T/6.

C.
12059.T/6.
D.
6025.T/6.
'
<
Huang
dan
Vi
tri xuat phat: 0„ = ( IOOTT.O) = 0 ' " " '
T
Lan
1 ma u =
0,5Uo
theo chieu am: t, = — .
6
Lan
2010 ma u =
0,5Uu
theo chieu am:
2010
T/6 ^'tW)-'
6
=>ChonB. • , , , ,^
Vi
du 6: Dat vao hai dau doan mach mot dien ap u = UocoslOOrct (V). Trong
chu ki thu 3 cua dong dien, cac
thoi
diem dien ap tuc
thoi

u c6 gia tri bang
dien
ap hieu dung la
A.
0,0625
s va
0,0675
s. V B.
0,0225
s va
a0275
s.
C.0,0025
s va
0,0075
s. j . ' D.
0,0425
s va
0,0575
s.
% • I ' ••/ •"'
Huang
dan
Cdch
1: Gidi
phuang
trinh
luong
gidc.
' ;

Bidttff USn thiic V^t It LTDH
trSn
kenh VTV2. t4p 2 - Chu Van Blgn
Chu
ki thu 1: u =
•COSl007tt = -
Chu
ki
thu-
2: {
It^
=t2+T
=
0,0375(s)
'-^->
'tg
=ti +2T =
0,0425(s)
[t, =t2
+2T = 0,0575 (s)
Cdch
2: Diing vdng iron luong gidc. ' <! '"
•
Vi
tri xua't phat: 0^=0
• I n
:.f
1,
Chu
ki thu 3:

Lan
1: O, =- ti =
' 4 ^
-0
0)
IOOTI
7t
„ Oj-Og
Lan
2: O, = — + 2;: => to =
(0
=
0,0025(s)
- +271-0
_^
IOOTI
=
j=i>ti
=0,0025(s)
= -j + 27r=>t2
=a0]75(s)
' 'J 1)
i'.f;i
;TV„.if.;
1
{
=
0,0225(s)
:.}:£rifiJ
Chu

ki
thiV
3:
t5
= ti +2T =
0,0425(s)
i' ' ^^"'^ •
^
^
=> Chon D. '?r.'
tg
=t2 +2T = 0,0575 (s) • -
Chii y: Ncu khong han chcboi dieu
kien
dang tang hoac dang gidm thi ung v&i mot
diem
tren true ung vai hai diem tren vdng trdn lugng gidc
(trit
hai vi tri Men).
Do do, trong chu ki dau tien c6 hai thai diem ti vn ti; chu ki thu 2 c6 hai tlwi diem
f.3 = ti + T vd t4 = ti + T;
t2i,vi
= ti + nT vd
tiu^i
= ti + nT. Ta co the rut ra 'meo' Idm
, , So lan
f neu
dU
1
=> t = nT + t, ,., , „

nhanh:
• =
n<^
, ,
2 [neu dU2=>t = nT +
t2
-'iiu/
iTlW
Vi
du 7: Dong dien
xoay
chieu qua mot doan mach co bieu thuc i = Iocos(1007rt
- n/3) (A) (t do bang giay). Thoi diem thu 2009 cuong do dong dien tuc
thai
i
= Io/V2 la
A. t = 12049/1440 (s).
C.t
= 24113/1440 (s).
2009
; ; , .1 B. t = 24097/14400 (s).
D.t
= 22049/1440(8).
Huang
dan
T
Ta tha'y: = 1004 dU 1 ^ t2oo9 - 1004T + t^,
Ta dung vong
tron
luang

giac
de
tinh
ti:
t
^24
>
«,':-»U,l/:i.J'
T 24097
t2oo9 = 1004T + — =
^~-(s)
^ Chon B.
IK
Cty Timii PTTV DVVn Kbang VJ^
Chu
y: Trong mot chu ki c6 4 tliai diem de /u / =b< Uo. Detim thai diem lan thie
n
md lul =h ta can luu y:
Lanldenu^
ld:ti.
Lan
2 den Id :
Lan
3 den
u-i
Id : .
Lan
4 den Id : t4.
loo':.
Lan 4n +1 den Id:

t4„+]
= nT + tj
Lan 4n + 2 den Wj la : i^^x+Z = nT + t2
Lan 4n + 3 den la : t4,-,+3 = nT +13
Lan 4n + 4 den la : t4n+4 = nT + t4
neu
dif
1
=> t = nT + tj
, , Solan
Ta CO
the rut ra meo lam nhanh: = n<;
4
neu
dif 2 => t = nT + t2
neu
du 3 => t = nT + t3
neu
dif 4 => t = nT +14
:2
A,
Vi
du 8: Dong dien
xoay
chieu qua mot doan mach co bieu
thiic
i = Iocos(1007it
- n/3) (A) (t do bang giay). Thai diem thu 2013 gia tri tuy?t doi ciia cuong
dp dong dien tuc
thai

bang cuang do dong dien
hi^u
dung la gt) ^hmr
A.
t = 12043/12000 (s). (A) K:V-M B. t = 9649/1200 (s). (A) £ ,
v
C.t = 2411/240 (s).
Ta nhan tha'y: ' •'
2013
= 503 du
1
^ t2oi3 = 503T + tj.
Ta
diing
vong
tron
lugng
giac
de
tinh
ti:
T
D. t = 12073/1200 (s).
Huong dan
••) f:V
12013
24
= 503T +
-
12073T 12073

24
24 1200
(s) ^ Chon D.
\'
-'^)=-*3
3) Cac gia tri tuc thoi 6 cac thoi diem
Neu biet gia tri tuc
thai
6
thai
diem nay tim gia trj a
thai
diem khac ta co
the giai phuang
trinh
lugng
giac
hoac
dimg vong
tron
lugng
giac.
Vi
du 1: (DH-2010) Tai
thai
diem t, dien ap u = 200 ^2 cos{1007tt - n/2) (trong
do u
tinh
bang V, t
tinh

bang s) co gia tri 100 V2 (V) va dang giam. Sau
thai
diem do 1/300 (s), dien ap nay co gia trj la j 'f j f
A. -100 V. B. 100 V3 (V). C. -100 ^2 (V). D. 200 V. ST
Huang
dan
Cdch
1:
U(t^)
=200V2cos
OOti —
^ 2
U(,l
= -200o)sin cot
= IOOV2.
7t
7t ^ 5n
COti — = — => coti = —
^23
^6
17
B6
trjf
kie'n
thiic
V^t li
LTBH
tren
kcnh
VTV2.

t^p 2 - Chu VSn
Bien
ti +
300 j
=
200V2cos
^ 1 '
71
CO
t1 + —
V
^
300>
t1 + —
V
^
300>
2_
=
-100^/2(V)=>ChonC.
Cdchl:
Khi
u = 100 V2 (V) va dang giam thi pha dao dong c6 the chon: = - .
Sau thai diem do 1/300 (s) (tuang ung vai goc
quet
Acj) = (oAt =
1007t/300
= 7t/3)
thi
pha dao dong: O2 = + AO = — f

=>U2
=200V2cosO2
=-100>/2(V)=>ChonC.
,,, .
Vi du 2: Dong dien
chay
qua mot doan
mach
c6
bieu thiic i =
4cos(1207it)
(A), t do
bang
giay.
Tai thoi diem ti nao do, dong dien c6
cuang
do 2V3 A. Deh thai diem t = ti + 1/240 (s), Z
cuang
do dong dien
bang
J- ' •
A.
2 (A)
hoac
-2 (A). B. - V2 (A)
hoac
2 (A).
C. ->/3 (A)
hoac
2 (A). D. Vs (A)

hoac
-2 (A).
Huong
dan
Vi
khong Hen quan den chieu dang tang
hoac
dang giam nen ta c6 the giai
phuong
trinh
lugng
giac
de tim nhanh ket qua.
=
4cosl207tti
= 2V3
1207iti
=±^
Cuang do dong dien a thoi diem t = ti + 1/240 (s):
i
=
4cosl207i
ti
+•
1
240
4
COS
1207rti
+-

2J
= 4
COS
6 2.
= ±2(A)
Vi d\ 3: Dong dien
xoay
chieu
chay
qua mgt doan
mach
c6 bieu thiic
i
= 2 V2
cos(1007it
+ (p) (A), t
tinh
bang
giay (s). Vao mot thai diem nao do,
1= sfl Ava dang giam thi sau do it nhat la bao lau thi i = + V6 A?
A.
3/200
(s). B.
5/600
(s). C.
2/300
(s). D. 1/100 (s).
Huang
dan
Cdchl:

•'^•i^f>fi-"
3
T T. T T 3T
t
= +
—
+ — + —
=:
=
12 4 4 6 4 200
(s)=^Chon
A.
__l—^
-A
0 0,5A 0,5AV3
Cty
mHHnTVDVVHlihang
Vl^,
Cdch
2: Khi i = N/2 (A) va dang giam thi pha dao dong c6 the chon: Oj = —,
3
thoi
diem gan nhat de i = ^/6 (A) thi pha dao dong O2 = -
—
+
2T[
.
6
' - -^ + 2TC-~ •
00 A q 3

Do do, thoi gian: ti = — = — ^ = (s) => Chon A ' '
0)
lOOTt 200^
Vi
du 4: Vao cung mot thoi diem nao do hai dong dien
xoay
chieu h =
Iocos(cot
+
cpi
va i2=
Incos(cot
+ 92)
CO
ciing trj tuc thai
0,5^/3
lo, nhung mot dong dien dang
tang con mot dong dien dang giam. Hai dong dien nay
lech
pha nhau
A. 7t/3. B.
271/3.
C. 7t.
Huong
dan
Cdchl:
:"'=,'"v;:r
i,=IoCos(cot.cpO
=
-^^^^^^^^^_.

i'l
=-WIQ
sin(cot
+ (pi) > 0
^/3Io
\2 = IQ cos (cot + 92) =
-
2
=>(cot
+ cp2) = -
D.7C/2.
V,;,
LA
2 1
6
i
'2 =
-COIQ
sin (cot + (p2 ) < 0
^
Acp
= - => Chon A. '
Cdchl:
Dua vao vong lugng
giac,
hai dong dien
xoay
chieu c6 cung tri tuc thai
0,5 ^/3 lo, dong dien dang giam iVng vol niia tren con dong dien dang tang
ling

voi nua
duoi.
Hai dong dien nay
lech
pha nhau la Acp =
—
Chon A.
,• ' .3
BAITOAN
LIEN
QUAN
DEN Dl|N
LlT^NG
Phuong
phdp
giai
1)
Dien
lugng
chuyen
qua tiet dien
thang
day dan
Theo
dinh
nghia:
i
= ^
dt
dq

= idt.
Dien lugng chuyen qua tiet dien thang ciia day dan
tinh
tu thai diem ti den
B6
tr^
ki&'n
thiic
V$t
li
LTOH
Iren
kenh
VTV2,
t$p
2
—
Chu
VSn
BlSn
i
= Io
sin(cDt
+
(p)=>Q
= -
—cos(cDt
+
{p)
(0

Inr
i
=
IQ
cos(«)t
4-
(p)
=>
Q =
—sin((Bt
+
cp)
CO
Inr
COs(cot2
+(p)-COs(03tj
+cp)
=
—rsin(cot2
+(p)-sin(ff)ti
+(p)
tt)
Vi
du 1:
Dong
dien xoay chieu chay
trong
day dan c6
bieu
i =

2cos(100Kt
- 7t/6)
(A)
(t do bang
giay).
Tinh
di^n
luong
chuyen qua
tiet
di^n thang
ciia
day
dan
trong
l/300{s)ke
til-liic
t = 0.
• ^ • •
>
A.
6,666 mC. B. 5,513 mC. C. 6,366 mC. D. 6,092 mC.
Huang
dan
Cdchl:
,."\)t
.A''
t2
Q=
Jidt

=
1/300
2cos
^OOTtt ^
3
dt
=
-
IOOTT
-sin
lOOTCt
1/300
>
6,366.10"^ (C)
0
=>
Chon
C. :
ji .ji
Cdch
2:
Diing
may
tinh
casio Fx 570ES, chon don vj goc la rad va bam
phim
I
tren
may
tinh

de
tinh
tich
phan.
Chu
y: De tinh dien lugng chuyen qua
tiet
dien thang cua day dan trong thai gian
At
ketit
luc dong dien bang 0, ta c6 the lam
theo
hai
each:
•
|nK:
/i-
Cdch
1: Gidi phuang trinh i = 0
detim
ra ti
tl+At
,. I„
sau do tinh tich phan: Q= idt • , .;
'1
O
Cdch
2: Viet lai bieu thuc dong dien duai
dang i =
IQ

sin
cot
vd tinh tich phan -i^
ft'
•
At J
t
(S)
Q=
Jl(,sincotdt
=
—(1-coscoAt)
(tich phan nay chinh Id dien tich phan to mdu
tren do thi).
CO
vi du 2: Mac day dan vao nguon xoay chieu on
djnh
thi dong dien chay qua c6
bieu
thiic
i = 2cos(1007it - n/3) (A).
Difn
lugng
chuyen qua
tiet
dien thang
cua day dan
trong
thoi
gian 1/300 s ke tu

liic
t = 0 va ke tie
liic
i = 0 Ian
lucrt
la ,
A.
5,513 mC va 3,183 mC. B. 3,858 mC va 5,513 mC.
D.
87 mC va 3,183 mC.
Huang
dan
^
C. 8,183 mCva 5,513 mC.
dt
'2
•
dq
=
idt=>Q=
jidt
'1
ciyfimnnrv
D
vvn
Khang
vl^t
1
/
300

Qi
=
2cos
dt
Q2
=
«
5,513.10"-* (C) "
1/300 ^
i
1
2sin(1007rt)dt
vJ().»V
«
3,183.10"^ (C)
=>
Chon
A. ' ;
Vi
du 3:
Dong
dien xoay chieu chay
trong
day dan c6 tan so goc co.
Dien
lugng
chuyen
qua
tiet
di§n

thang cua day dan
trong
1/6 chu ki dong dien ke tu
liic
dong
dien bang khong la
Qi.
Cuong do dong dien cue dai la
A.
6Q1C0.
B.
2Q1C0.
C.
Qico.
D. 0,5.Qico. 'V
Huong
dan ,
.^-lUih
u',1,
'J '
-i ;
•
= i =
1(,
sincot
=>
dc]
=
I,)
sincot.dt

/yii,
dt
T/6
J
•Q,
= [
]osincotdt
= —
271
-cos
—
t
T
nT/6
In
Jo
2ci)
>
Ig
=
2coQ,
=>
Chon
B.
Chu
y:
1)
Dong dien
den
chieu luc no

triet
tieu
i = 0.
2)
Khodng thai gian hai
Idn
lien
tiep
dong dien
triet
tieu
Id T/2 nen dien lugng chuyen
qua
tiet
dien thang cua day dan trong thai gian do
la:
f ,.
;
j
0/i'.,1
:A
*;
T/2
•iT/2
IQ
sin cotdt =
—(1
- cos
cot)
CO

T/2
2I0
0
CO
Den
mm chu ki
tiep
theo
cUng
co — dien liiyng chuyen ve nen dien lugng
(0
chuyen
qua
tiet
dien thdng cua day dan trong mot chu ki la bang 0 nhung do Idn
4Ir
dien lugng chuyen dichuyen
vela
|Q|^
= —
(0
0
\
Do
Idn dien lugng chuyen qua
tiet
dien thang cm day dan sau Is vd sau thai gian t
lanlugtld
]^\Q\j
vd

^\Q\^.
Vi
du 4: Cho dong dien xoay chieu i =
27csin(1007tt)
(A) (t do bang
giay)
qua
mach.
Tinh
do Ion dien
lugng
qua mach
trong
thoi
gian 5
phiit.
A.
600'C. B.
1200
c. C. 1800C. D. 2400 C.
Huong
dan
|Q|
= 1|Q| = t—^ = 5.60.— = 1200(C) ^
Chon
B.
T
271 CO 27t
21
Bd

trg
kie'n
thitc
V^t It
LTDH
tr^n
kSnh VTV2.
t^p 2 - Cha Van
Blin
2)
The
tich
khi
thoat
ra
khi dien
phan
dung
dich
axit
H2SO4
+ Dien luong
qua
tiet dien thang
cua day dan
trong
1/2 chu
ky: Q1/2
=
2Io/co.

+
The
tich khi H2
va
O2
0
DKTC thoat
ra 6
moi
di§n
cue
trong
nua chu ki Ian
Q
lugtla:
=
;^n,2(l)
va
=-^5,6(1).
1/2
96500
'
^
' '
96500
+
The
tich khi
H2
va

O2
6
DKTC thoat
ra 6
moi dien
cue
trong thoi gian
t
Ian
V
r
va Vf^. =
•—
VT
. .
T
+ Tong
the
tich khi H2
va
O2
6
DKTC thoat
ra 0
moi dien
cue
trong thoi gian
t
t
luotla:

=^^1
va =^^2-
la:
V =
VH2+VO2=-(V,+V2).
Vi
du
5:
Cho
dong dien
xoay
chieu
i
=
7:sin(1007it)
(A)
(t
do
bang
giay)
chay
qua
binh
dien phan chiia dung djch
H2SO4
voi
cac
dien
cue
tro. Tinh

the
tich khi
H2
6
dieu kien tieu chuan thoat
ra
trong thoi gian
16
phiit
5
giay
6
moi dien
cue.
A.
0,168
lit.
;
\,:
B.
0,224
lit.
C.
0,112
lit.
D. 0,056
lit.
Huong
^an
Qi/2=2^

= 2-^
= 0,02(C)
^ •
ft)
IOOT:
t
Qi/2
.n,2 =
^:^ll,2
=
0,112(l)=>C/ip/7C.
"2
T
96500""
0,02
96500
Vi
du
6:
Cho
dong dien
xoay
chieu
c6
gia
tri hieu dung
2 A
chay
qua
binh dien

phan
chua
dung djch H2SO4
voi
cac
dien
cue
tro.
Tinh
the
tich
khi
0
dieu
kien tieu chuan thoat
ra
trong thoi gian
16
phut
6
moi dien
cue.
A.
0,168
lit.
B.
0,0235
lit.
C.
0,047

lit.
D. 0,056
lit.
'
Huong
dan
V
=
VH2+VO2=Y
^'/^ ll,2
+ -^.5,6
300
0,02
0,018
96500
.11,2 +
96500
0,018
96500
96500
.5,6
=
0,047{\)=>ChgnC.
[
Cty
Timn nrv P
VVH
Khang
Vlft
BAI TOAN LIEN QUAN DEN MACH RLC NOI TIEP

phtiong
phdp
gidi
1)
Tong
tro, dp
l?ch
pha, gia tri
hi#u
dung
Tong
tro
Z
=
VR'+(ZL-ZC)'
IT",
if
Do
lech
pha:
tan(p
=
Z|
-Zc _UL-U
R
.,AiX r
(p
> 0: u sdm pha
hdn
i

mach
c6
tinh
cam
khang
9 < 0: u tre pha
hdn
i =>
mach
c6
tinh
dung
khang
(p
= 0 : u,i
Cling
pha.
^
. , U UR UL UC
Cuong
do
hieu dung
I
=
— = —= —- = =
—-
„
Z
R ZL Z(- Zj^^ -ml nid iob gnoriW
Dien

ap
tren doan
mach
U^N
=
12^^
=^ZMN
Vi
du
1:
Mach dien noi tiep
gom
dien tro
R = 60
(Q),
cuon
day
c6
dien
tro
thuan
r
=
40(Q)
CO
do tu cam
L =
0,4/7i(H)
va
tu

dien
c6
dien dung
C =
l/(147t)(mF).
Mac
mach
vao
nguon dien
xoay
chieu
tan
so goc
IOOTT
(rad/s). Tong
tro
ciia
mach
dien
la
A.
150
Q.
B.
125 Q.
C.
100
V2
Q.
D.

140
;
>=
S
j
Huong
dan \
ZL
=wL =
10071.—
=
40(Q);Zc
=
^
(oC
IOOTC.
10"
147t
=>Z
=
^(R +
r)^+(ZL-Zcf
=Vl002+(40-140f
=100^2
(Q)'
=> Chon
D.
'i)i'>
nan ,
•

du 2:
Dat mot
di$n
ap
xoay
chieu
vao hai dau mot
doan
mach
mac noi
tiep
gom
tu
dien
c6
dung khang
200Q,
dien
tro
thuan
30N/3Q
va
cuon
cam
c6
dien tro 50 ^f3
Q
CO
cam
khang

280Q.
Dien
ap
giua
hai dau
doan
mach
A.
som pha hon
cuong
do
dong dien
la n/4.
B.
sdm pha hon
cuong
do
dong dien
la
Ti/6.
C.
tre pha hon
cuong
do
dong dien
la n/4. j ,
D.
tre pha hon
cuong
do

dong dien
la
71/6.
•
>
23
B6
tr^ hien thiic V^t
li
LTBH trSn
kenh VTV2.
t^p 2 - Chu
Van Bl&n
Huong
dan
_
ZL - Zc _ 280 - 200 _ 1
^"^^
R + r ~30>/3 + 50>/3 ~ Vs
.{p =
^>0
=>
Dien ap sam pha hon dong dien => Chon B
Vi
du 3: Mot mach dien mac noi tiep
theo
dung thu tu gom dien tro thuan
R
= 30 Q, tu dien 1 c6 dien dung =
1/(3TC)

(mF) va tu dien 2 c6 dien dung
C2 =
I/TT
(mF). Dien ap
giiia
hai dau doan mach la u = 100N/2 coslOOTit
(V),
Cuang do hieu dung trong mach la -' ' .
rir: _il,':i
n,>i •
A.
1,00
A.
B. 0,25 A. C. 2 A. _ D. 0,50 A.
.
Huang dan
^
^ -^ = 30(Q),
Zc2=
^ ^
Zo=-
(oC
lOOn.
^37t
coC
K
7^ = 10(Q)
Z
=
^R2

+ (Zci +
Zc2f
= 50(Q) ^ I = - = — = 2(A) ^ Chon C.
Vi
du 4: (DH-20n) Dat mot dien ap xoay chieu c6 gia trj hieu dung va tan so
khong doi Ian krot vao hai dau dien tro thuan R, cuon cam thuan c6 do tu
cam L, tu dien co dien dung C thi cuong do dong dien hieu dung qua mach
tuong ung la
0,25A;
0,5A; 0,2A. Neu dat dien ap xoay chieu nay vao hai dau
-
doan mach gom ba phan tu tren mac noi tiep thi cuong do dong dien hieu
dung qua mach la
^,
A. 0,2 A.
B.
0,3A. C. 0,15 A. D. 0,05 A.
,
Huang dan
U
U
R = —;ZL=—;Zc
=
0,25 0,5
U
0,2
1
=
U
>^+(Z,-Zj^

•
=
0,2(A)=>Chon
A.
V0,25^
.0,5 0,2J
Vi
du 5: Cho mot mach dien mac noi tiep gom mot dien tro R = 40(Q),
cuon cam thuan c6 do tu cam L =
0,8/Tr
(H) va mot tu dien c6 dien dung
C
=
2.10-V7T
(F). Dong dien qua mach c6 bieu thuc la i = 3cos(1007Tt) (A).
Dien
ap hieu dung giua hai dau doan mach la i-' •
A.60V.
B.240V. C. 150
V.'^f'"!'
D.75V2V.
Huang
dan
1
1 . „ , 0,8
Zc
=
coC
100 ^:!^
33-

=
50(Q);ZL
=roL
=
1007:.—= 80(Q)
71
Z
= ^R^
+(ZL
-Zcf =
50(Q) =>
U =
IZ
=
75V2
(V)
Chon D.
Vi
du 6: Cho mach dien xoay chieu RLC mac no'i tiep
theo
dung
thii
tu gom
cuon thuan cam c6 cam khang 14 (Q), dien tro thuan 8 Q, tu dien c6 dung
khang 6 (Q), biet dien ap
gifra
hai dau mach c6 gia tri hieu dung la 200 (V).
Dien
ap hieu dung tren doan RC la
A.250(V).

B.
lOO(V).
C.
125V2(V).
D.
100V2(V).
Huong
dan <j/
^
U -rori fir:
\J.IR^
+Zr r- n ,-CI :
URC
=
IZRC
= ^ZRC = , , ^ , = 12572
(V) =^
Chon C.,,
_
„
Vi
du 7: Cho mach dien xoay chieu tan so 50 (Hz) noi tiep
theo
dung thu tu:
di^n
tro thuan 50 (Q); cuon day thuan cam c6 do tu cam
0,5/7i
(H) va tu di^n
CO
dien dung

0,1/?!
(mF).
Tinh
do lech pha
giira
va u^c- -
A. 71/4.
B.
7i/2.
C. 37r/4. D.
7i/3.
"''
, Huang dan , , ^
Z, =a)L
= 50Q,Zc =
=
100fi
,, d I
Si
J f: :
(oC ''<• -0 -// V/
^
'
J,.I>I
itoiim.nt}ob
}om oxt) 'M tp.
tan
(PKL
= ^ = 1 =>
(pKL

=
—
-h-nUh
i\-i'Q-u{
ml JU
J'J ,;?'J
i^:.,
Z,
- Zr 71 ^ • •
tan
(PLC
= Q
=^=»9LC=-^
:'m.&)t?i
,
vf;
"'^
(''^''5t'c'L.(i
i.dq
^Jit
=> 9RL
-
^LC
= — ^- ''^
*^>v OS
(b(5i)
rxS.O
6j-kj
I'll
Vi

du 8: (DH-2008) Cho doan mach dien xoay chieu gom cuon day mac noi tiep
voi
tu dien. Do lech pha ctia dien ap giua hai dau cuon day so voi cuong do
dong dien trong mach la
7T/3.
Dien ap hieu dung giua hai dau tu dien
bang
^y3
Ian dien ap hieu dung giCra hai dau cuon day. Do lech pha cua dien ap
giua hai dau cuon day so voi dien ap giua hai dau doan mach tren la
A.
2n/3. B. 0. C.
TI/2.
'^'''-V;
D.
- n/3. ^"
^f-'o
o-v-
Huangddn y-^ '
2 •?m
Ki>3
mu'j
1/}
oQ
'
>K
•••
tancpcd =-^ =
tan-=>ZL
- V3R

0
.g :
JH0v
V!
=
^ o
>2^Z2
= 2R = ^ Zc
=
273R
.^.^^ , .^
Zl
—
Zp nr 7t 271 „, . M J
tan
(p
=
—^=
~ = -^y3=>(p =
=>
ro^.j
- 9 = —
=>
Chon A.
Vi
du 9: Dat dien ap xoay chieu vao hai dau doan mach AB
theo
thu tu gom
cuon day thuan cam L c6 cam khang
100

Vs Q, dien tro R =
100
Q va tu dien
C
CO
dung khang 200^3 Q mac noi tiep, M la diem
gii>a
L va R, N la diem
giua
ciia
R va C. Ket qua nao sau day khong diing? '
251
Bo
trg
hiSn
thiic V^t li
LTDII
tren
kcnh
VTV2,
14p 2 - Cliu Vsin Bien
A.
Dien ap giCra hai dau dpan AN £ R C
''
sam pha han dien ap giua hai A / hy~j \~^B
dau doan mach AB la
27T/3
B.
Cuong do dong dien tie pha 7i/3 so vai dien ap giua hai dau doan mach AB.
C. Dien ap

giiia
hai dau doan AN som pha hon dien ap
giiia
hai dau doan
mach AB la
2TT/3.
D.
Dien ap
giiia
hai dau doan mach AB som pha han dien ap
giiia
hai dau
tu
dien la 7i/6. . ,,, •" • •
Huong
dan
ZL-Zc
_
10073-200V3
n
ZL
IOOV3
r- n
tancpAM
= —^ = = v3 =>
COAM
= —
NAN
^ MAN 3
7t

= —
> 0 : u^B s6m hdn u^ la
—
=> Chen D.
6 6
2J
Vi
du 10: Cho mot doan mach RLC khong phan nhanh (cuon day cam thuan).
Goi UR, UL,
UC Ian lugt la dien ap hieu dung
giiia
hai dau dien tra thuan,
hai dau cuon day va hai dau tu dien. Bie't
UK
=
UL
= 0,5Uc thi dong dien qua
mach se:
A.
tre pha 0,257i (rad) so voi dien ap giiJa hai dau doan mach.
B.
tre pha 0,57T (rad) so voi dien ap hai giua dau doan mach.
C. som pha
0,25TI
(rad) so voi dien ap
giiia
hai dau doan mach.
D.
som pha 0,5n (rad) so vol dien ap giira hai dau doan mach.
Huong

dan i ,
,
tancp
=
==^^^^-^
= -1=^9 = ^ Chen C.
Vi
du 11: Dat dien ap 50 V - 50 Hz vao doan mach noi tiep gom dien tra 40Q
va cuon day thuan cam thi dien ap hieu dung giira hai dau cuon cam la
Ui.
= 30 V. Do tu cam cua cuon day la
A.
0,4/(71
N/2)(H).
B.
0,3/71
(H). C. 0,4/(7i )(H). D.
0,2/7t
(H).
"
Huong dan
U^
=
U|
+
U^
50^
=ul+
30^
r:>

UK
=
40(V)
' ' ' '
=.I
= HK.f^.,(A)^Z,=Hk = ^ = 30=>L = ^ = M(H)=.ChonB.
R
40 ^ ^ I 1 M 71 ^ ^
Vi
du 12: Cho mach dien xoay chieu khong phan nhanh RLC, cuon day thuan
cam va Zi, = 8R/3 = 2Zc. Dien ap hieu dung
giiia
hai dau doan mach la 200
H
V. Dien ap
hi§u
dung giiTra hai dau dien tro R la
A.
180 V. r* r; B. 120 V. C. 145 V. D. 100 V.
Cty
T/VHH
nrv D VVH Khang Vift
Huong
dan
5R
Z
=
JR2+(ZL-ZC)'
=
UK

=IR
= —R = ^R =
120(V)^Chon
B.
Chu
y: Thay doi link kicn tinh dim dp
U
=
Juf,+(UL-Ucr
ZL=n,R
Zc = n2R
=>UK=?
[U2^ui
+
(UL-Uc)'
Vi
du 13: Doan mach xoay chieu noi tiep gom dien tra thuan R, tu dien C va
cuon cam thuan L. Dat vao hai dau doan mach mot dien ap xoay chieu on
djnh
thi dien ap hieu dung tren R, L va C Ian lugt la
60V, 120V
va
40V.
Thay C boi tu dien C thi dien ap hieu dung tren tu la
100 V,
khi do, dien ap
hieu dung tren R la ' '
A.
150 V. B. 80 V. C. 40 V.
Huong

dan
UK=60(V)1
UL
=120(V) '
D.
20^/2 V.
Zl
= 2R:
Uc=40(V)=^U
=
^Ui^+(UL-Uc)
=100(V) ;
Khi
C thay doi thi U van la 100 V va
U'L
=
2U'K => U^
= U
R
+
(U'L- U'cf
=>100^
=U'K
+
(2U'K-100)^
^U'K
=80(V)=>Chon B.
Vi
du 14: Doan mach xoay chieu gom bien tro R, tu dien C va cuon thuan cam
L

mac noi tiep. Khi dieu chinh bien tro 6 gia trj nao do thi dien ap hieu
dung do
dugc
tren bien tra, tu dien va cuon cam Ian lugt la 50V, 90V va
40V.
Dieu chinh de gia trj bien tro Ion gap doi so voi luc dau thi dien ap
hieu dung tren bien tro la - i
A.50V2
V.
UR=50(V)
UL
-40(V)
Ue =90(V)
B.
lOOV.
C. 25 V.
jiji
=
D.
20V1OV.
Huong
dan
Zc=l,8R
= 0,9R' •^?-M,;>vt.h^r.5i
ZL
=0,8R = 0,4R' , ,
U
= Juf^+(UL-Uc)
=V50^+(40-90)2
=50V2(V)

U^
= U
'I +
(U
'L
- U c
)^
=> 50^2 = U + (0,4U
'K
- 0,9U
'K
)^
=>U'K
=20VT0(V)=:^Chon D.
27
Bo
trg
kie'n
thitc
V^t
IILTDH
trSn hcnh
VTV2.
t^p 2 - Chu
VSn Blen
______
Vi
du
15: Mot macii dien gom mot cuon
day

ccS dien
tro
thuan
r he so tu
cam
L
noi
tiep
voi mot tu
dien
C
duoc
mac vao mot
hieu dien
the
xoay chieu.
Cu'ong
do
hieu dung
cua
dong dien
qua
mach
do
dugc
I = 0,2
A. Hieu dien
the hieu dung giua
hai dau
doan macii,

gifra
hai dau
cuon day,
giira
hai ban
tu
dien
c6
gia
trj
Ian lugt
la
120 V, 160 V,
56
V. Dien
tro
thuan ciia
day la
A.
128Q.
B.480£l
C. 96 Q.
D. 300
Q.
>Kii,
.Si
:•<•':Huangddn
^ .
=
U? +

(UL
-
UC
f =
U?
+ -
2ULUC
+ =
U^L
- ^^L^c
+
Uc >
120^
=
160^
-
2UL.56
+ 56^ =>
UL
=
128(V)
r
= ^ =
480(Q)=>ChonB.
^«'^'^
^^-^
1602=U?j=U?+U[=i>Ur=96:
Vi
du
16:

Dat mot
dien
ap u =
20
^y2
coslOOrtt (V),
(t do
bang
giay)
vao hai dau
doan mach gom dien
tro R
noi tiep voi cuon
day c6 he so tu cam L =
0,12/7:
(H)
va
dien
tro
thuan
9 Q thi
di§n
ap
hi?u dung tren
R la 5 VS
V.
Hay
tinh
dien tro R.
'

^'''">
« " J\
A.30Q.
B.25Q. C.20Q. D.15Q.
Huong
dan
3
'
x2
16,
U,
r 3
=
(UK
+
U,f
+ U[ => 400
=
(5>/5
+
U,)'+ ^U? => U, = 375 (
V)
R
UR
-=^R
= -r =
15(Q)=>Chon D.
U,
3 3 ^ '
Chu

y:
Co the can
ci'c
vao gid
tri
tiir
thai tinh do lech pha. ,t:
,jQ
u
=
UoCos(cot +
(p)
^,f,V,
•/()<•'
,,VOr.
jiJ
i
=
iocosa)t=>
71
(Ot
+
-
2,
n
Mt
2.
U1
=
U()L

COS
VAi;V,S)* uc=U„cCos
thi
ta se tun
dinrc
(cot
+
(p)
=
iaj;
chon dau avig hoqc
trif
dc'sno cho
.
Khi cho biet cdc gid
tri tuc
tiioi
u
=
U|
UL
=U2
UQ
- U3
mt
+ -
mt
l
2v
l

2
=
vd
phdi
km
71
(ot
2J
<((ot
+
(p)<
7t
cot
+
—
2
Tit
do
se
tiin du'o'c
<p.
'
-u
, ; '
•
• •
Vi
du 17:
Mach dien xoay chieu
noi

tiep AB
gom
dien
tro
thuan
R,
cuon
cam
thuan
L va tu
dien
C
(R, L,
C
khac
0 va
hCru han). Bien
do cua
dien
ap
giua
hai
dau
doan AB
va
tren
L Ian
lugt
la
Uo

va
UOL.
6
thoi
diem
t
dien
ap tuc
98
Cty
T/VHH
fllTV
D VVH
Kbang
Vl^t
thoi
hai dau
doan mach AB
bang
+0,5Uo
va
dien
ap
tiic
thoi
tren
L
bang
+UOL/72
.

Dien
ap
giua hai
dau
doan mach
A.
som pha hon
dong dien
la 7i/12.
B.
som pha hon
dong dien
la
71/6.
C. tri
pha han
dong dien
la 7t/12. D. tre pha han
dong dien
la
71/6.
Huong
dan
i
=
In coswt:
u
=
U() cos(())t
+

(p)
= i^=>
(rot
+
(p)
=
± —
2
3
U
=
U()L
COS
(o)l+(p)<
2)
rot
+ —
2,
7t
U
OL
72
rot
+ —
2,
_^
71
(rot
+ cp)
= • '

i?
=
-—<0:utre phahcfn
i
=> Chon
C.
rot
+ —
2
n
4
Chu }/:
Niju cho gid
tri
tire thai dien dp
a
hai tlwi diem
tin van
c6
the
tinh duvc
cp.
Vi
du
18: Mach dien xoay chieu noi tiep AB
tan so 50 Hz
gom dien tro thuan
R,
cuon
cam

thuan
L va tu
dien
C (R, L, C
khac
0 va
hi>u
han). Bien
do
ciia
dien
ap
giua
hai dau
doan AB
va
tren
L
Ian lugt
la
Uo
va
Uoi,.
6
thai diem
ti
dien
ap tuc
thoi
giua

hai dau
doan mach AB
bang
+0,5Uo
va sau
khoang
thoi
gian ngan
nhat
1/400 s
dien
ap tuc
thoi
tren
L
bang
+UQI./72
.
Dien
ap
giiia
hai dau
doan mach
A.
som pha
hon dong dien
la 7t/12.
B.
sam pha hon
dong dien

la
7t/6.
C.
tre pha
hon dong dien
la 7i/12.
D.
tre pha han
dong dien
la
71/6.
Huong
dan
u
=
UQCOs(rot +
(p)
• ' ' •
i
=
I()COSrot:
UL
=
UOL COS
u
=
UoCos(l007rti +(p)
=
rot
+

-
2
Uo
U
=
UQL COS
IOOTI
ti
+
1
400
7t
+ —
2
U,
OL
72
1007rt
+ ^ +
i^
4
2
• (p
=
—
>
0
:
u
s6m hdn

i la
— =>
Chon B.
6
6
7t
\,,
,,.r,,.vi
Chii
11:
Ne'u cho gid tri
dien
dp tuc
thoi
vd
dong
dien
a
hai
thai
diem
tinh
dugc
<p.
u
=
Uo coslOOTit-
u=uo
va
u

gidm
(tang)
t=to+At
-»roto
=?
i
=
lo cos(1007it
-
(p) _-i^IQ^^l-
->(p
"
1
=
0
vdigiam
(tang)
^
=
?
*
A
29
Bo
trp
kien
thiic V^t
liLTDIl
tren
henh

VTV2. t^p 2 - Chu VSn Bien
Vi
dy 19: Dat di§n ap
200V
- 50Hz vao hai dau doan mach AB gom dien tro
thuan
25^2 mSc noi tie'p voi doan mach X. Cuong do dong dien hieu dung
qua doan mach la 2 A. Biet 6
thoi
diem to, dien ap ti'rc
thoi
giua hai dau AB
CO
gia trj
200V
va dang tang; 6
thoi
diem to + 1/600 (s), cuong do dong dien
tuc
thoi
qua doan mach bang 2A va dang giam. Tinh do lech pha ciia dien
ap giua hai dau doan mach AB so voi dong dien qua mach va cong
sua't
tieu
thu
dien cua doan mach AB va doan mach X. ^
„•-,,,,,.•
ft;.,
Huang
dan

''t•'•
u
=
200^/2coslOOTtt-
t=to
u
=
200
Lid
u
tang
-^lOOTito
=
i=2^/2cos(1007^t-(p)-
i
=
2vd
\
IOOTI
tn+-
600
-9
71
4
=>
(p
=-—< 0 : Dien ap
UAB
tre pha hon i la 7:/3.
Cong

suat
tieu thu dien cua doan mach AB va doan mach X Ian lugt la: t i
P = Ulcoscp =
200(W)
va Px = P - l^R = lOO(W).
Vi
du 20: (DH - 2012) Dat dien ap u =
400cosl007tt
(u
ti'nh
bang V, t
tinh
bang s)
vao hai dau doan mach AB gom dien tro thuan 50 Q mac no'i tie'p vol doan
mach X. Cuong do dong dien hieu dung qua doan mach la 2 A. Biet 6
thai
diem t, dien ap tuc
thoi
giua hai dau AB c6 gia tri 400 V; 6 thai diem
t
+ 1/400 (s), cuong do dong dien tuc
thoi
qua doan mach bang khong va
dang giam. Cong
sua't
tieu thu dien cua doan mach X la
A.
400W.
B.200W.
C. 160W. D. lOOW.

Huang
dan
t=o
u
= 400cosl007Tt >u = 400 (V)
i
=
2V2cos(1007tt-(p)-
t=o+
400
i
= Ova
\
IOOTT
=P-Pj^
= Ulcos(p-I^R =
200(W):
400
Chon B.
7t n
=
-=>(p = —
2 4
4-,.i
V'V:''
2) Bieu thiic
dong
di^n va di^n ap
Viet
bieu

thirc
theo
phimng
phdp
truyen
thong:
Io =
Un
U
OR
U
R
01.
U
oc
U
Z
= VR^+(ZL-ZC)-
ZL-ZC
Zc
ZMN
OMN
tanq) =
•
R
tancpMN
=
R
-Z
-z r

MN
/
MN
30
Cty
TISHH
nrv DVV11 Khang Vi^t
a) Ne'u cho i =
Iocos(cj)t
+ cp;) thi
u
= I()Zcos(cot + + cp) . xiU •
U]^
=I()Rcos(cot + <pi)
UL
=IoZLCos(cot + 9j+7i/2) ; ;
Uc
=IoZ(;COs(cOt
+ (Pi -7l/2)
"MN
=IoZMNCos(cot +
(Pi+9MN)
b) Neu cho u =
U,)Cos(cot
+
(p^,)
thi i =
-^cos(a)t
+
ip^

- (p). ',
. c) Ne'u cho u^N =
UoMNCOs(a)t
+ a) thi i = ^'^^
cos(o)t
+ a -
tp^N
)
•
Sau khi vie't duoc bieu thiic ciia i se vie't dugc bieu thuc cac dien ap
khac
theo
each
lam tren.
Vi
du 1: Mot mach dien xoay chieu mac noi tie'p gom dien tro thuan R = ISQ,
cuon thuan cam c6 cam khang
ZL
= 25Q va tu dien c6 dung khang Zc = lOQ.
Ne'u
dong dien qua mach c6 bieu thuc i = 2 V2
cos(1007rt
+ 7c/4) (A) thi bieu
thuc dien ap hai dau doan mach la . , , ' . .r
A.
u =
60cos(1007tt
+ 71/2) (V). B. u = 30 V2
cos(1007it
+ 7r/4) (V).

C. u =
60cos(1007tt-7i/4)(V).
D. u =
30^/2cos(1007ct-7r/2)(V).
Huang
dan
ZL
= ft)L = 25Q
Zr
=
1
coC
•
u = IijZcos
= 10Q
Z
= ^/R2+(ZL-Zcf = 1572
tancp =
Z,
-Z
7t
R
= l=>(p =
—
>0:u sdm hon i Id —
4
'l007rt + ^ + ^l
4 4J
=
2V2.I5V2COS

1007rt
+
7C
(V):
. ,. 4,
Chon A.
Vi
du 2: Mach dien xoay chieu gom dien tro 30 Q, cuon day c6 dien tro thuan
30Q va
CO
cam khang 40Q, tu dien c6 dung khang lOQ. Dong mgch chinh c6
bieu thuc i =
2cos(1007:t
+ 7t/6) (A) (t do bang giay). Viet bieu thuc dien ap
giiia
hai dau doan mach chiVa cuon day va tu
dif
n.
A.
ULrC
=
60cos(1007it
- 71/3) (V). B.
ULrC
=
60cos(1007it
+ 7l/4) (V).
C. ULrc=60V2cos(1007:t-7t/12)(V). D.
UL^C
= 60 V2

cos(1007it
+ 57r/12) (V)
Huang
dan
ZtrC
= +
(ZL
- Zc f =
30V2Q
HI lu. ,
tan(pLrC
=
?^ =
1
=> cpLfP = — > 0
:
ULrC
h^'^
^
~
r
4 4
"LrC
=IoZLrCCOS
•
Chon D.
1007rt
+ ^ + ^
6 4,
=

60^y2(
cos
1007tt
+
57t
12
(V)
31
Bo
trp klSn
thiic
V^t li
LTDH trcn henh
VTV2,
t4p 2 - Chu V0n
Blen
Vi
du 3: Mot
cuon
day
thuan
cam c6 do tu cam 1/n (H) va tu
dien
c6
dien
dung
2.10-'/TI
(F)
ghep
noi

tie'p,
roi no! hai dau
doan mach
vao
nguon
c6
dien
ap u =
100
V2cos(1007it
+
Tt/6) (V). Dong dien
qua
mach
la
A. i =
2cos(1007it
+
71/2)
(A). B. i =
2cos(100Tit
-
7t/2)
(A).
C. i
=2
^/2
cos(100Ttt
-
71/3)

(A). D. i
=
2 V2
cos(1007Tt +
7t/2)
(A).
Huong
dan
Z,
=wL
=
100Q;Zc
= —= 50Q
wC
"ri'T,''!'
*• ^••••I'rrin'J
w orb
w^l/i
(cf
- irii
(o
+
}fc)r!',o,.^f,,,,0 ,„>^fU
or!';
ir^VI
(./
Z,
-Zr 7t , , ., TT
•jV'ub ,h>*v
U68

—1^ =
+cx)=>(p
=
—
>0:ii
sC/n p/ia
/iCw
ila—
,
.2
2
.H'-iii
iBfil-'i^r,:* canJ
Z
= +(ZL
-Zc)^
= 50Q
tan
(|)
=
.
U,
0
-COS
7t
7t
1007rt
+
6
2,

lOOTTt
3.
(A)=>Chon
C.
Vi
du
4:
Mot
doan mach
gom
cuon
day c6
do tu
cam
0,6/7i
(H) mac
no'i tiep
vai
mot
tu
dien
c6
dien dung
1/(14?:) (mF).
Dat vao hai dau
doan mach
mot
dien
ap
xoay chieu

c6
bieu thuc:
u
=
160cos(1007it
-
71/12)
(V)
thi
cong suat
tieu
thu
trong mach
la
80 W. Bieu thuc cuong
do
dong dien trong mach
la
A. i
=
2cos(1007it
-
7i/6)
(A). B. i
=
72
cos(1007tt
+
n/6) (A).
C. i =

V2
cos(1007:t
+ 7i/4)
(A).
D.
i
=
V2
cos(1007it
-
7c/4)
(A).
,
,
Huong
d^n . ^ ^
ZL
=(OL =
60(Q);Z(
= =
140(Q)
coC
.A
auii
P
= I^R =
-
U^R
R^+(ZL-Zcf
•Ail

\y.o
•
=> 80 =
•
80 2.R
+(60-140r
.,•1" r
-
i
• 1 '))
R
= 80(Q)
tanq)
=
—
•"it
f9.
R
^
=
-1
=>q)
=
—
<0:utre
pha han i
let
—(i
sdm pha
hcfh

u)
4
4
Z
=
+(ZL-Z(;)^
=
80>/2
(Q)
ii=—cos
lOOTTt-
—+
-
=V2i
12
4
cos
1007tt
+
-
6J
(A)=>Chon B.
Vi
du
5: Dat
dien
ap
xoay chieu
u =
10cos(1007it

+
7t/4)
(V)
vao hai dau
doan
mach
noi
tie'p
gom mot
tu
di^n c6
dung khang 30Q, dien
trd
thuan R =
lOQ,
va cuon
day
c6
di^n
tra
thuan
lOQ c6 cam
khang lOQ. Viet bieu thiic
di^n
ap giiia
hai dau
cuon
day.
A.
ucd =

5cos(1007it
+
37C/4)
(V). B. ucd =
200 ^/2 cos(1007tt
+ n/6) (V).
C.
Ucd
=
200cos(1007tt
+
Tc/6)
(V).
D.
Ucd
=
5cos(1007it
+
7t/4)
(V).
32
Cty
Timn MTV !>
V
VII
Khang Vift
Huang
dan
Z
=

^{R
+
rf+{Z^_-Zcf
=20V2(Q)
ZL-ZC
, n
z,d
=Vr^Tzf
=
ioV2(n)
tanked
= —=
l=>(Pcd
=7
4
r
Bieu thuc
u^d
som
hon u la
cp^j -(p =
^
vaUocd
= ^'^cd "
^^^ ^^"^
= ^(^)
Dodo:
u,a
=U(,cdCos
4

2
= 5cos 1007lt +
371
(V)=^Chon
A.
Vi
du
6:
(DH-2009)
Dat
dien
ap
xoay chieu
vao hai dau
doan mach
c6 R, L,
C
mSc
noi
tie'p. Bic't
R = 10 Q,
cuon
cam
thuan
c6 L =
0,1/71 (H),
tu
dien
c6
C

=
0,5/7t
(mF)
va
dien
ap
giita
hai dau
cuon
cam
thuan
la
^ ^
ui
=
20
V2
cos(l 007it
+ 71/2)
(V). Bieu thuc dien
ap
giira
hai dau
doan mach
la
A.
u
= 40cos(l
OOTtt
+ 7t/4)

(V)
B.
u
=
40cos(1007ct
-
7t/4)
(V)
C.
u
= 40
N/2
cos(l 007it
+ 71/4)
(V)
D. u
=
40-Jl cos(1007it
-
7:/4)
(V)
Huong dan
^
^
[Z
=
7R'+(ZL-ZC)'
=
1072fi
z,-z. 7:

^^'.^fa'^"
Z,
=coL
=
10(Q);Z(;-
= = 20(0)
71
tan
(p
=
-^
=
-l=>(n
=
R
4
Dien
ap
u
tre hon
i la
7r/4
ma i
tre pha han
UL
la
7r/2
nen
u
tre pha hon

UL
la
371/4 va
U(,
=
z,
Do do: u =
UnCos
-Z
=
40(V).
(
n 3n^
f A
1007Ct+
= 40cos
lOOTtt
I
2 4 y
l
4;
(V)^ChonB.
Vi
du
7: Doan mach xoay chieu khong phan nhanh
gom cac
phan
tu
theo dung
thu

tu:
dien
trd
thuan
30
(Q),
cuon
day
thuan
cam c6
do tu
cam
0,6/7c
(H)
va
tu dien
CO
dien dung
IOO/TI
().iF). Dien
ap
giiia tren doan mach
chi gom
cuon
cam
va tu
dien
c6
bieu thuc
ULC

=
160cos(1007rt
-
7t/3)
(V)
(t do
bang giay).
Bieu thuc dong dien
qua
mach
la
A. i
= 4V2
cos(1007tt
+ 7t/6)
(A). B. i
=
4cos(1007tt
+ 7t/3)
(A).
C. i = 4cos(1007tt
-
Ti/6)
(A).
D.
i
=
4cos(1007tt
+
n/6)

(A).
:
ih
:
'
Hudtigdan
' }
./
ZL
=wL
=
60Q;Zc
= =
100Q; ZLC
=^0
-^C)
=
40<^
tancpL^;
=
hon)
Z,
-Z
•
(PLC
= -— <
0
:
ULC
tre P^a hon

i la
7i/2
(i
som pha
33
BS
trp
klih thiic
V^t It
LTDtl
tr&n k6nh
VTV2.
t$p 2 - Chu
VHn Bien
=>
1
=
100Kt (pLC
=
4cos
lOOrtt-
(A)=>Chon
D.
Vi
du 8:
(DH-2010)
Dat
dien
ap u =
Uocoscot

vao hai dau
doan mach
gom
dien
tro
thuan
R,
cuon
cam
thuan
c6 do tu cam L va tu
dien
c6
dien dung
C mac
noi
tiep. Goi
i la
cuong
do
dong dien
tuc
thoi
trong doan mach;
u,,
U2
va
U3
Ian
lugt

la
dien
ap tuc
thoi
giira
hai dau
dien tro, giua
hai dau
cuon
cam
va giCra
hai dau tu
dien.
He
thuc dung
la ^ ^
A.
i
=
-
R2
+
coL
-
\
• .I'i
(>,f'i/
;.j';Hn
(oC
. •.

ftifi
.'.pil
^opt
"^hn
D.
i =
(oL
Huang
dan
Chi
Ui
Cling
pha
vdiineni-
— ^
Chon
C.
•;'ir-:
Chu y: Neu eho biet bieu thuc u,
i
thi ta se tinh duge trakhdng.
Vi
du 9: Mot
doan mach
gom
cuon
day c6
dien
tro
thuan 100

Vs Q, c6 do tu
'
„ cam L
noi tiep voi
tu
dien
c6
dien dung 0,00005/7t (F).
Dat vao hai dau
doan
•
mach
mot
dien
ap
xoay chieu
u
= Uocos(1007rt
-
Tt/4)
(V) thi bieu thuc cuong
do dong dien
tuc
thoi
qua
mach
i
=
V2
cos(1007tt

-
7c/12)
(A).
Xac djnh L.
, .
A.
L
= 0,4/71
(H).
B.
L
=
0,6/TI
(H).
C.
L
=
1/n
(H).
D. L
=
0,5/::
(H).
Huang
dan
1
r.r.r.,^^
^
Zr-Zc
1

ZL-200
"
^ -
=200(fi);
9
= 9^,-cpi =
—
=>tan(p =
-
^ c_ _ L
(oC
R
V3
IOOV3
ZL
=
lOO(Q)
=0
L
= -(H) Chon
C.
Vi
du 10: Dat
dien
ap
xoay chieu
u
= U V2 coslOOnt (V)
vao hai dau
doan mach

noi
tiep gom dien tro
R
= 50
Q,
cuon
cam
thuan
L va tu
dien
C
thi dong dien
•'V;
i'
qua
mach
c6
bieu thuc
i
= 2
V2
cos(1007rt +
7t/4)
(A).
Goi
UL
va Ian
luot
,
la

dien
ap
hieu dung tren
L va
tren
C. He
thuc
diing
la
A.
UL
-
Uc = 100
V.
B.
Uc
-
UL
=
100 V.
C.UL-UC
=
50V2 V. ,^
D.UC-UL
=
100V2 V.
Huong
dan
(p
=

-
ZL-ZC
=
tan—=>UC-UL
=
100(V)
Chon
B.
R
IR 4
Chu
ij:
Neu c6 dang sin thi doi sang dang
cos:
sin
(cot
+
a)
=
cos
cot
+
a —
2.
Cty TlSHtlnrvDVVHKhang
Vl^t
Vi
du 11: Dat
dien
ap u =

U(icos(cot
+
7i/4)
(V)
vao hai dau
doan mach
gom
dien
tra thuan
R va
cuon
cam
thuan
c6 do tu cam L mac no'i
tiep
thi
cuong
do
dong dien
qua
doan mach
la i =
Ii)sin(ci)t
+ 57r/12)
(A).
Ti so
dien
tro
thuan
R

va
cam
khang
cua
cuon
cam la
A.
1/V3. B.
1.
C.0,5V3.
Huong
dan
,
D.
V3.
U
=
UyCOS
03t
+
—
4
i
=
In
sin
cot
+
12
=

locos
on
n
(Ot
+
12
2,
=
I„cos
n
Z, n r-
Vi
du 12: Mot
cuon
day
khong thuan
cam noi
tiep
voi tu
dien
C
trong mach xoay chieu
c6
dien
ap u =
Uocoscut (V)
thi
dong dien trong
mach
s6m pha hon

dien
ap u la
c|)i
va
dien
ap hieu dung
giira
hai dau
cuon day.la
30 V.
Neu
thay Ci
= 3C thi
dong dien cham
pha
hon
u goc
c|)2
= 90"
-
c|)i
va
dien
ap
hieu dung
giua
hai dau
cuon
day la 90
V. Tim Uo.

A.I2V5V.
B.6V5V.
/
Mt-
V
12
y
R
1
75
C.30V2
V.
D.
60 V.
Cdch
1:
-2C
Huang
dan
;
I2
^=31,;
ij som pha hon u; 12 tre pha hon u;
I,
112.
Hinh
chieu
cua 0
tren
I la 0,^

U2LC
=
U2L
-
U2C
=
UlRzO
3ZL - ZC = R (1)
UILC
=
UIC-UH.
=
U2K
r:i>Zc-Zl,
=
3R
(2)
Tu
(1)
va
(2) =>
ZL
=
2R; Zc
= 5R
Ban
dau
Uo
=
I„Z

=
u
OKL
Z
RL
Z=
-X
JR^+(2R-5R)^
=60(V)
=>ChonD.
VR"
+4R
Cdch
2:
Zi
-Zr ^ ^
ZC-ZL
<
0 =>
tan
(Pi
=
tan
(-cpi)
= - -~ -
R
=
IZ„,
=
u

R^+Z
'R-+(Z,-Zcf
=
30
/J
W4
A)
tUi trp kiSn thiic V$t
IILTBH
trSn
henJt VTV2. t4tp 2
-
Chu VSn Blen
K
K
Theo
bai ra: 91
+
92
=
90" nen
tan(pitan(p2
=
1 hay
= 90
^
'^^
^ ^
=
1

=>
R =
J(Zc
-
ZL)(Z,
-
Zc
/
3)
U'
cd
U
cd
R2+(ZL-Zcr
R2
+
z,
-"^
Zc^
3;
(ZC-ZL)
+
(ZL-ZC)'
Z,
-
(ZC-ZL)
+
z,
-
Zc^

90
30
(ZC-ZL)
=
3
=^
Zc =
2,5ZL
^ R =
0,5ZL
, j.^;
^.^^^^
.gj.^
j
, ,fl
Thay gia trj nay vao bieu thuc UCJ:
(0,5Z,,)^+Zf^
=
30=>Uo
=60(V)
V2^(0,5ZL)'+(ZL-2,5Z,J
BAI
TOAN LIEN QUAN DEN BIEU DIEN
PHl7C
Bi'eH
thuc
Dang phuc trong
may
FX-570
Tong

tro
Z
=
7R^+(Z,,-Z,)^
Z
=
R
+
i(Z,
-Z^)
(vol
i
la
so ao)
ffn'n
.ji :J5
ZMN
=
A/I^MN
+
(ZLMN
"
ZCMN
)
ZMN
=
I^MN
+ '
(ZLMN
~

^CMN
)
Zi.
=
Z, i,
Ze
=
-Z(_i
(vol
i
la
so ao)
Dong dien
i
=
IQ cos(iut
+
(P|
)
i
=
I(,Zcpi
Di^n
ap
u
=
U(, cos (cot + cp^,)
u
=
UoZcp,

Dinh
luat
6m
,
U ^ . u
I
= —
nhiina
i
=A
—
Z
Z
u
-
ZMN
'^un >
• I-'MN
ZMN
U
=
IZ
nhi/ng 11
7^
iZ
u
= iZ
UMN
=
IZ^4N

n/if/n^
"MN
''ZMN
LIMN
= ^Z^N
u
"
y
"MN
=
g'^MN
Cty TISHll
nrv
DVVH Khang
Vlft
ZMN
^-MN
ZMN
••MN
Z,
Zr Z
MN
Bieu thiic dong dien:
i =
=•
= —
Cai
dat
tinh toan
vai

sophitc trong
may
tinh casino
fx-570es
tti
+
BAM
MODE
!_
(De cai dat tinh toan vdi
so
phuc)
(De cai dat hien thi so phtic dang
A Z
9)
BAM
SHTFT
MODE
V
+
BAM
SHTFT
MODE
4
(De cai dat don
vi
goc
la
rad).
1) l^ng dung viet bieu thuc

Vi
du
1:
Dat mot dien
ap
xoay
chieu
u =
200cos(]007it
+
7i/3)
(V)
vao
hai dau
mot doan mach
mac noi
tiep
gom
tu
dien
co
dung khang 50Q, dien
tro
thuan
50Q
va
cuon cam thuan
co
cam khang
lOOQ.

Tinh tong tro ciia mach.
Dien
ap
giCra
hai dau
doan mach
som hay tre pha hon
dong dien trong
mach bao nhieu? Viet bieu thuc dong dien trong mach.
Huang
dan
Ccich
1:
Cdch truyen thong
Z
=
^R^
+
(ZL
-
ZC
f -
50V2
(Q)
tancp
=
Zl
-
Zp
^ 7t „ , t . ,v 'V

= lr=>(p
= — >0:u sdm
hdn 1
la —
4
R
.
200
1
= cos
1007rt
+
^-^
3
4,
= 2^/2
cos
1007tt
+
4
n
12
i
tre hdn
u
la —
4;
(V)
Cdch
2:

Dung
mdy
tinh
cam tay
casio
570es
Cai
dat
tinh toan
vai so
phuc trong
mdy
tinh casino
fx-570es
+
BAM
[MODE|
g
(De cai dat tinh toan v6i
so
phuc)
' ''
+
BAM
^HTFT
[ ^0DE|
0 g
§](De cai dat hi^n thi so phuc dang
A Z
(p)

+
BAM
^HTFT
|
^0DE|
Q
(De cai dat don
vi
goc la rad)
Z
=
50V2(O)
Z
= R +
i(ZL-Zc)
=
50
+
1(100-50)
=
5072Z-«^
71
•V
UoZcp,
Z
R +
i(ZL-Zc)
50
+
1(100-50)

200Z-
3
=272Z-^
12
0
1
=
2N/2COS
1007lt
+
n
12
(A)
B6
trg klS'n thiic
V$t
li
LTOH tren henh
VTV2.
tap 2 - Chu VSn
Bien
Thao
tac
Hien
thi tren man hinh
[5^R[ENGl0plOOlR^[)]R|
SHIFT
I^^R
CMPLX
R

Math
50
+
i(100-50)
50V2Z-7r
4
i.'.A'''
i
•.'•lA^
CMPLX
R
Math
50
+
i(100-50)
50V2Z-7r
4
Tong tra la 50
\/2 Q
va dien ap som pha hon dong dien la n/4.
Thao
tac
Hien
thi tren man hinh
•
•
•
.J.i;;^"j,
y
iim^Jt^.*

••'f.Mv
CMPLX
R
Math
200Z-^Ans
'
3
• 2^/2Z — TC
12
200
SHIFT
(-)
•
•
•
.J.i;;^"j,
y
iim^Jt^.*
••'f.Mv
CMPLX
R
Math
200Z-^Ans
'
3
• 2^/2Z — TC
12
(-)
•
•

•
.J.i;;^"j,
y
iim^Jt^.*
••'f.Mv
CMPLX
R
Math
200Z-^Ans
'
3
• 2^/2Z — TC
12
SHIFT
xlC* V
3
>
+ Ans
SHIFT
1213
=
CMPLX
R
Math
200Z-^Ans
'
3
• 2^/2Z — TC
12
CMPLX

R
Math
200Z-^Ans
'
3
• 2^/2Z — TC
12
Bieu thi'fc dong dien
i = 272
cos
100Trt
+ —
12
(A)
Vi
du
2:
Dat dien
ap
xoay chieu
u =
220^/2
cos(1007it
+ n/3)
(V) vao hai dau
"doan mach
theo
diing
thii
tu gom dien tro thuan

R =
50Q, tu dien
c6
dien
dung
C
=
100/7i()j,F)
va cuon cam thuan c6 do tu cam
L =
0,5/7r(H) mac noi tie'p.
1) Tinh tong tro ciia mach. Dien
ap
giiia hai dau doan mach som hay
tre
pha hon dong dien trong mach bao
nhieu?
2) Viet bieu thiic cua cuong do dong dien tiic thoi qua doan mach.
3) Viet bieu thuc dien ap
6
hai dau
chua
R
va C.
v
4) Viet bieu thiic dien ap
6
hai dau
chua
C

va L.
" ' t
^
v;.
i,
J"''?!'
Huong
dan
.
^,
•.^.'''r''
ZL
=coL
=
50(Q);Ze
= —= 100(Q)
1)
Z = R +
i
(ZL
-
Zc)
= 50 +
i
(50
-100) =
5072Z
- <=>
Z
=

50V2(Q)
7t
Tinh
tong tro ciia mach la 50
yfl
Q; dien ap tre hon dong dien la 7i/4.
UoZcpu
220>/2Z-
3
o\
_ _
'~Z
~ R +
i(ZL-Zc) "50
+
i(50-100)
=
4,4Z^
12
•
i
=
4,4 cos
lOOTCt-
7K
12
(A)
220N/2Z-
3) URC
=

iZRc
= "
ZRC
= :
^(50
+
UO
-100))
«
491,935Z0,725
'
Z 50 +
1(50-100)^
^ '
URC
=
491,935cos(1007rt
+
0,725)(V)
'
11*'
r
Cty T/SHHnrvDVVHKhang Vift
4) UcL =
l^CL
S-^CL
-
220^/2Z
^-
^

(0 +
1(50-100))
=220Z
—,
50
+
1(50-100)
^ UQI
=220cos
lOOTtt-
12
(V)
12
vi du 3: Mot mach dien xoay chieu mac noi tie'p gom dien tro thuan
R =
15Q,
cuon thuan cam
c6
cam khang ZL
= 25r} va tu
dien
c6
dung khang ZQ
=
lOO.
Neu dong dien qua mach
c6
bieu thuc 1
=
2

V2
cos(100Tit
+
7t/6) (A) thi
bleu thuc dien ap gii>a hai dau doan mach
la
A.
u =
60cos(l
OOKt
+
571/12)
(V).
B. u =
30
V2
cos(1007it
+
7i/4)
(V).
C.
u =
60cos(1007rt
-
7i/4)
(V). D.
u =
30 N/2
cos(1007rt
-

57r/12)
(V).
Huong
dan
u
=
i.Z
=
2V2Z-]x(l5
+
i(25-10))
=
60Z
—
6 y
12
u
=
60cos
1007lt
+
5TC
12
(V)
=> Chon A.
FX-570ES:
Bam
2j~
SHIFT
(-) 30y (

|15||
+
||ENG|
(
25 10
)
)
Tren
man
hinh
272Z30
x
(15 +1(25 -10))
' {
60Z75
Fx
-
570MS:
Bam
|2N/2||SHIFT1[(-)
30[xj
(
|15||+||ENG|
(
[25jy[l0j
) )
1
H
Bam ISHIFTI [(+)J
R

se
dUdc
UQ
=
60.
Bam
|SHIFT|
9 se dMc
cp^,
=
75.
Vi
du
4:
Mot doan mach dien xoay chieu noi tie'p
theo
diing
thu tu gom cuon
cam thuan
L c6
cam khang 30Q, dien tro
R =
30Q
va
tu dien
C c6
dung
khang 60Q. Dong qua mach
c6
bieu thuc 1

= V2
cos(1007it
+ nl6)
(A). Viet
bieu thuc dien ap glQ-a hai dau doan mach chiia LR.
A.
ULR
=
60cos(1007ct
+
57r/12)(V).
B.
ULR
= 60^/2
cos(100Kt
+
57r/12)(V).
C.
ULR
=
60V2cos(1007rt-7t/3)(V).
D.
ULR
=
60
>/2
cos(1007it
+
7r/3) (V).
Huang

dan
5%
"LR
=
I-ZLR
=
=> ULR
=60COS
^
V2Z-1X
(30 +1 (30
-
O))
=
60Z-
6
J 12
So07rt
+
—
12
(V) Chon A.
39
Bo
trg
kicn
thiic
V^t
IILTDII
trcn

Renh
%rrV2.
t^p 2 - Chu VSn Bl£a
Fx -
570ES:
Bam
2 >
SHIFT
(-)
30
30
ENG
30
Trenmanhinh
%/2Z30x(30
+
i(30-0))
60Z75
' '
•
'
rT:"ji:1:vft'io;:;
i'Sjii:
'itirff
u-:il?1'">''\,'i~<,^>;'
£>''::i.iij
-liii'ttK
'N'M •'•].
'iiS'':
30

Fx -
570MS:
Bam
2
SHIFT
(-) 30
ENG
30
)
)
Bam
I
SHIFT
I
[(+)| [=] se
duac
C/,„ ^ = 60. Bam
[SHIFT
|
y se
(fu^tfc
cp^^ =75.
Vi
du 5: Dat dien ap
xoay
chieu u = 220 ^/2 coslOOTit (V) vao hai dau doan
mach
gom dien tro thuan R = 55Q mac noi tiep voi tu dien thi
cong
sua't

tieu thu
tren doan
mach
la 440 W. Bieu thuc cuong do dong dien qua doan
mach
la
A.i
=
4cos(1007tt-7t/4)
(A). B. i = 2 V2
cos(100Trt
+ 7i/4) (A).
C. i =
4cos(1007rt
+
K/4)(A).
D. i = 2
N/2
cos(1007tt
- 7i/4) (A).
y-'-
Huang
dan :
,•••/'<-
p = rR =
U-R
22072
•440
=
220\55

55^ + Zc
Ze=55(Q)
u
" Z "
55+1(0-55)
= 4Z
—T:
<=> i =
4cos
4
1007lt
+ -
4,
(A)i^ChonC.
Vi
du 6: Mot doan
mach
gom cuon day c6 dien tro thuan 100N/3 Q, C6 do tu
cam l/n (H) noi tiep voi tu dien c6 dien dung
50/TC
().iF). Dat vao hai dau
doan
mach
dien ap: u = 200N/2
cos(]007it
-
TC/4)
(V). Bieu thiic dien ap tiic
thoi
tren cuon day la

A.
u,d = 200 ^/2
cos(1007rt
+
7t/12)
(V).
B. u.^ =
100>/2
cos(1007it
+ 7r/6)
(V).
ti
C. u^d = 200 N/2
cos(1007tt
+ n/6)
(V).
D. u.^ = 100 ^/2
cos(1007ct
+
7:/12)
(V),
•g/vju
Huang
dan
[Z,=coL
=
100(Q)
r^^,,i(2^_2^)
^ -
Zc =

coC
=
200(Q)
Z-H
=r +
iZ
^_
200N/2Z-~
X
(lOoVs + i.lOO) =
200-j2Z~n
<=> u^H =
200V2cos
1007tt
+ -
12
(V) => Chon A.
Vi
du 7: Cho doan
mach
xoay
chieu noi tiep
theo
dung thu tu gom cuon cam
thuan 1
CO
do tu cam Li =
0,1/?:
(H), dien tro thuan 40 Q. va cuon cam thuan
2

CO
do tu cam L2 =
0,3/71
(H).
/in
Cty
TnmnnrvDVVHKltang
y/ft
Dien ap 6 hai dau doan
mach
u = 160 V2 coslOOTit (V). Viet bleu thuc dong
dien qua
mach
va
tinh
dien ap hieu dung tren doan
mach
chua
RL2 .
A.
i =
2N/2cos(1007it
+
7t/6)(A)va
U i^^^
= WO (V).
B. i = 2N/2 cos(]OOTit + n/4)
(A)
va
URL2

= 60 (V).
.,.j;f^
[ ; .
C. i =
4.cos(1007tt
- 71/6) (A) va
URLJ
= (V).
D.
i =
4cos(1007it
- 7C/4) (A) va U^LJ = 100 V2 (V).
Huong
dan
ZL,
=COLI
=10(Q)
=«L2
=30(Q)
. _ u _
I6OV2
'"Z~40
+ i(10 + 30)
Z
= R + i(ZL-Zc)
z
1
71
= 4Z 7:»i =
4cos

lOOnt —
4 I 4
(A)
UKL2
= I-ZRL2 =
2V2.5O
=
100V2
(V) ^ Chon D.
Vi
du 8: Cho
mach
dien
xoay
chieu gom dien tro thuan R, cuon day thuan cam
L
va tu dien C = 1/n mF mac noi tiep. Neu bieu thuc ciia dien ap giCra hai
ban tu dien la
Uc
= 50%/2
cos(1007Tt
- 37T/4) (V) thi bieu thiic ciia cuong do
dong dien trong
mach
la ^
'i^^'^'-'^"^
f-^-'
A.
i = 5 V2
cos(1007rt

+
37r/4)
(A). B. i = 5 x/2
cos(1007:t)
(A),
C. i =
5N/2cos(1007rt-7r/4)(A).
D. i =
5cos(100Trt
-
37i/4)
(A).
- !
Huang
dan
Zr
=
J IOQ
u
50^/2Z-^-
^
(oC =>i = ^ = ^ = 5x/2Z 7r
Z
0 +
i(0-10)
4
Z
= 0 +
i(0-Zc)
i

=
5V2i
cos
lOOTlt
(A)=>ChonC.
Vi
du 9: Mot doan
mach
xoay
chieu noi tiep AB gom dien tro lOOQ, cuon cam
thuan
CO
cam khang lOOQ va tu dien c6 dung khang
200Q.
Biet
dien ap tuc
thoi
gii>a
hai dau cuon cam c6 bieu thiic ui. =
100cos(1007Tt
- 7T/6) (V) (t do
bang
giay). Bieu thuc dien ap hai dau doan
mach
AB la
A.
u = 100 V2
cos(1007rt
-
1171/12)

(V). B. u = 100 V2
cos(1007tt
+
ll7t/12)
(V).
C. u =
50cos(1007it
+
7t/12)
(V). D. u = 50
N/2
cos(1007tt
+
7t/12)
(V).
Huang
dan
_6_x (100 +
1(100-200))
=
100^y2Z
r, .
ZL
lOOi ^ ^ 12
u
= iZ = ^Z = .
41
Bo
trffhicn
thiic

V^t li LTDH
tren
k&nh
VTV2,
t^p 2 - Chu VHn
Bien
u = 100N/2COS
lOOnt-
TTTT
12
)
(V)=>Chon A.
VI
du 10: Mot doan
mach
xoay
chieu no'i tiep AB
theo
dung thu" tir gom dien
tro
R = 25N/3 il, cuon cam thuan L c6 cam i<hang 75Q va tu dien C c6 dung
Ichang lOOQ. Diet dien ap tuc thoi tren doan
mach
chiia RL c6 bieu thuc
URi,
=
90cos(1007Tt
+ 7T/6) (V) (t do
bang
giay). Viet bieu thiic dien ap giira hai

dau doan
mach.
; » i ,0
A.
u = 30
cos(l
OOKt - 71/3) (V). B. u = 30 V2
cos(1007it
- 7r/3)
(V).
, '
C. u = 30 V3
cos{l
OOrtt + TI/6) (V). D. u = 30 V2
cos(l
OOrtt + 7r/6) (V).
Huong
dan
u
=iZ =
z
90Z'
Z =
-71
u =
30N/3COS
^-2— X
(25 73 + i (75
-100))
=

3073Z—
2573+
75i y ^ 3
1007lt
3,
(V)=:>Chon A.
2)
IJng
dung de tim hop kin khi cho biet bieu thiic dong dien
hoac
dien ap.
+
BAM ^0DE[
§] (De cai dat
tinh
toan voi so phiic) M y .if:
* Neu cho bieu
thCrc
dong dienva dien ap giita hai dau doan
mach
U
= U() cos (Ot +
Cp^i
) i,
: ,
;
i
= I()
COs(0)t
+ cpi )

i-:'''.'
JX
u
thi CO
the tim tro khang: Z = R + i(ZL
2 \ " _ UQ^^U
Vi
du 1: Mot doan
mach
xoay
chieu no'i tiep gom cuon cam thuan c6 do tu cam
0,6/K (H), dien tra thuan R va tu dien c6 dien dung C.
Biet
bieu thiic dien ap
gii>a hai dau doan mcich va dong dien trong
mach
Ian lugt la:
u=24072cosl00Tit(V)
vai =
472cos(1007it-7T/6)(A).
'
Gia tri cua R va C Ian lugt la :j, f >!
A.
30 Q va
l/(3n)
mF. B. 75 Q va
I/TT
mF.
C. 150 Q va
l/{3n)

mF. D.
30V3
Q va 1/(3TT) mF.
Huang
dan
Zj^
=(DL =
60Q=>Z
= R + i(Z, -Zc) = R +
i(60-Zc)
I'
Matkhac: Z = -= ^^^^ =
3073
+ 30i. Tir do suy ra: R =
3073(n)
va
,, - ^ 6 ,,,
60 - Zc =
30(fi)
=^ Zc = 30(Q) => C =
10
-3
(oC 3n
•
(F) =>ChonD.
Cty TiyHHMTVDVVnKhang VIft
Vi
du 2: Mot doan
mach
xoay

chieu gom dien tra thuan R mac noi tiep hop kin
X. Hop kin X
hoac
la tu dien
hoac
cuon cam thuan
hoac
dien tra thuan.
Biet
bieu thiVc dien ap giua hai dau doan
mach
va dong dien trong
mach
Ian
luot
la: u = 100 72
coslOOnt
(V) va i = 4cos(100Tit -
TI/4)
(A). Hop kin X la
A.
dien tra thuan 50 Q.
B. cam thuan voi cam khang Zi, = 25 Q. '
C. tu dien voi dung khang Zc = 50 Q.
D.
cam thuan voi cam khang Zi = 50 Q.
Huang
dan
Z = R + i(Z, -Zc) = ^ = ^ = 25 + 25i
, ' 4Z-^

R = 25(Q)
ZL
- Zc
=25(Q)
•
Chon B.
vi du 3: Mot doan
mach
chiVa hai trong ba phan tu: tu dien, dien tro thuan,
cuon cam thuan mac no'i tiep.
Biet
dien ap giua hai dau doan
mach
va
cuong do dong dien qua no Ian lugt c6 bieu thuc: u =
60cos(1007tt
- 7t/2) (V),
i
=
2sin(100Kt
+ 7r/6) (A). Hoi trong doan
mach
c6 cac phan tu
nao?
Ti'nh
dung
khang, cam khang
hoac
dien tro tuong ung vai moi phan tu do. Tinh
cong

suat
tieu thu ciia doan
mach.
,
•>
A.
R = 1573 Q;Zi, =
15QvaP
=
30(W).
, ; ,,„
B. R = 15 Q; Zc = 15 73 Q va P = 30 73 (W). '
C.
R = 15 73 Q;Zc = 15Q vaP = 3073 (W).
'
j'
D.
R = 15 Q;
ZI,
= 1573 Q va P = 30
(W).
\^^:"^^>r''
Huong
dan
Viet lai bieu thuc: i =
2sin(1007it
+ it/6) (A) =
2cos(1007it
- 7r/3) (A).
60Z-

Z = R +
i(ZL-Zc)
= - = ^ = 1573-151
2Z-
>^5i I' alt I't
j5»t/i'
R =
1573(Q)
ZL-ZC =
-15(Q):
Zc - 15(Q)
=i>
P = I^R = 3073(W)
Chon
B.
ZL=0
Vi
du 4: Dat vao 2 dau hop
kin
X (chi gom cac phan tu mac noi tiep) mot dien
ap xoay chieu u = 100cos(100Kt + TI/6) (V) thi cuong do dong dien qua
mach
i
= 2cos(1007it +
271/3)
(A). Neu thay dien ap tren
bang
dien ap
khac
c6

bieu
thuc
u =
400-72
cos(2007rt
+ 7i/3) (V) thi cuong dg dong dien:
i
= 5 72 cos(2007rt - 7i/6) (A). X c6 the
chiia
A.
R = 25 (Q), L = 2,5/7i(H), C =
10-*/7t
(F).
B. L =
0,7/71
(H), C =
10-3/(1271)
(F).
' 43
Bo
trp
hien
tiluc
V^l li L
TP
11
tren
kcnh
VTV2.
t4p2-Chu

V0n
Blin
C.
L =
1,5/7T
(H),
C =
l,5.10"V7t
(F).
D.
R = 25 (Q), L =
5/1271
(H).
•^"'•'f!
nv* y!
st.o:'
>, ||j
,5;
/ "is
.r >v:
lOOZ"
Z
= R +
i
(ZL
- Zc) = - = ^ =
-50i
=>
'
2Z

,271
3"
Z
= R +
2ZL
Z.^
u/"°^-^3
i
"572^-^^
6
R = 0 ^
TSMi!'.4.',
A,
R
= 0 xi'
•
i\'-A<"\\
,Ci
= 80i:
2Z,
= 80
f
Z,
=70(Q)
Zc
=120(Q)
L
=
0,7
(H)

IOOT:
7t r-u T3 • •
c
= —.IO^VF)
- „.
12%
•••"^ '>
Vi
dy 5:
Dien
ap a 2
dau cuon
day c6
dang
u =
lOOcoslOOTit
(V) va
cirong
do
dong dien
qua
mach
c6
dang
i =
2cos(100Trt
-
7r/3)
(A).
Dien

tro
thuan
cua
cuon
day
la:
A.25
72 Q. ' '
B.25a
C.
50 Q. D.125Q.
Huong dan
Cach
1;
I
72
•
R =
Zcoscp
=
25(Q) => Chon
B.
Cach 2: Z=-
= —^ =
25
+
43,3i
^ R =
25(Q)
1

2Z-60
^ '
Chu
y:
Mach
dien
dp
xony
chicu
AB
gom
hai
doan
mach
AM
(dd
bict)
va MB
(chua
biet)
mac
noi
dep.
Dexdc
dink
MB
ta dim vdo: Z^B
= = x
Z^M
-

i
"AM
Vi
du 6:
Mach dien
ap
xoay
chieu
AB gom
hai doan mach
AM va MB
mac noi
tiep.
Doan
AM gom
dien
tro
thuan
R = 50 Q mac noi
tiep
voi tu
dien
c6
dung
khang 50
Q,
doan
MB la
cuon
day c6

dien tro
thuan
r va c6 dp tir
cam
L. Biet bieu thiVc dien
ap
tren doan
AM va
tren doan MB Ian lugt
la:
UAM
=
SOcoslOOTit
(V) va
UMD
=
200
72
cos(1007Tt
+
77T/12)
(V). Gia
tri
cua
r
va
cam khang ZL Ian
lu-gt
la
A. 125QvaO,69H.

B.
75
Q va
0,69
H.
C. 125
Q va
1,38
H.
D. 176,8
Qva
0,976
H.
Cty TlSnn
MTV
D
VVH
Khang
Vl^t
Huong dan
20o72z^''
,'=>r,.v.
.
.
^
UAM
^ ^ ^
ZMB
=
-^ZAM

=
^?r^(50-50i)
=
125
+
i.216,506
ZAM
ZMB "AM »P
r
=
125(Q)
^ •
H.nLuri;:
7, Chon
A. '
'lui'r
It'i
(Si ' (
Z,.
=216,506^
L =
^^0,689(H)
' «.
'i,.,
(, ,
M
«/v n'i-)
iort
.(•/,
Vi

du
7:
Mot doan mach
AB
gom dien tro
R
mac noi tiep
voi
cuon day.
• ^
Biet dien
ap
giua hai dau dien tro
va
hai dau cuon
day
Ian lugt
la i,?,'
UK
=
120cosl007rt
(V) va
u^^
=
120cos(100Tct
+
K/3)
(V).
KeUuan nao khong dung?
,

•,;>;.v/i^v
A. Cuon
day
CO
dien tro
r
khac
0.
B. Dien
ap
giua
hai dau
doan
mcich AB tre pha
TI:/6 SO
voi
dien
ap
giija hai
dau
cuon day.
j>,^
,,•,;3
"
:
•
.'v
.:,
C. Di^n
ap

hi^u dung giCta hai dau doan mach
AB la
60 73
.
^
^
r-
• i
-itvA
'.I
r
•
D.
Fie so
cong suat cua doan mach
AB
bang 0,5 V3
.
^
• „ . (if
frH/U:!"inf>d
u'i
Huong dan
Dien
ap
hai dau doan mach: u^^,,
= u,^ + = 120
+
120Z—
=

12073Z —=> Chon C.
3
6
Vi
du 8: Mach dien
ap
xoay
chieu
AB
no'i tiep chi gom
cac
phan ti'r nhu dien tro
thuan,
cuon cam
va
tu dien. Doan mach
AB gom
hai doan mach
AM va MB
mac noi tiep. Doan
AM gom
dien tro
thuan
50
il
mac noi tiep
voi
tu dien
c6
dung

khang 50
Q.
Biet bieu thuc diC^n
ap
tren doan
AM va
tren doan
MB
Ian
lugt
la: UAM
=
80cos(100nt
-
n/4)
(V) va
u.vm
=
200
72
cos(1007it
+
TT/4)
(V).
Tinh
tong tro cua doan
MB va do
lech pha cua dien
ap
tren

MB so voi
dong
.i.
I
dien.
,
A. 250
Q va
TC/4.
" " p;:' •
B. 250
Q va -
TT/4.
QOS
C. 125
72
Qva-7T/2.
- D.
125
72 Q va TT/2.
Humtgd^n
^''•Vfmlq vV
20072Z
_
i
= ^ = ^ ^
Z„B
= ^
ZAM
=

^(50
-
50i)
=
250Z
^ .
^ ^
;
ZAM
^Mb "AM 80Z- '••
4
ZM[5-250(Q)
200^Z'^
%
=>ChonA.
(Sau khi
nhap
vao may
tinh
^(5O-50i)
VMB=-
80Z-^
neu
bam
phim
'=' thi
duoc
ket qua
176,77669
+

176,77669i,
con neu bam
'shift
2 3=' thi dixgc ket qua
250). AV,,
45
Bd
trphJSn
thitc
V$t IILTDH
tren
henli
VTV2.
t^p 2 - Chu Van
Bien
Vi
du 9: Dat vao hai dau AB mot dien ap xony chicu co gia trj hieu dung va tan
so khong doi. Doan mach AB gom doan mach AM noi tiep voi doan mach
MB.
Doan mach AM gom cuon cam thuan co cam khang 50 (Q) va dien tro
thuan Ri = 50 (Q) mac noi tiep. Doan mach NB gom tu dien co dien dung C
va dien tra thuan R2 mac noi tiep. Dien ap tuc thoi 6 hai dau doan mach
AM
va MB Ian lugt la
UA.\
= 200cos(100Tit +
TI/6)
(V) va
UMH
=

100cos(1007Tt
-
57T/12) (V). Hoi tren AB tong cam khang nhieu hon hay it hon tong dung
khang bao
nhieu?
Tinh tong tra cua doan mach AB. Tinh do lech pha cua
dien
ap tren AB so voi dong dien. Tinh he so cong
suat
cua mach AB.
Huong
dan
Tong tro phuc toan mach:
';yniil,.
' ' ' • '- • ' (! }-i»>i
ZAB
-
"AM
+
"MB
V
"AM
AM
-
'0 ni.rlii
1
+•
-'MB
'AM
J

'AM
-
^"'lOOZ-^^
1
+
-
12
200Z-
71
(50 + 50i).
Sau khi nhap vao may
tinh
so'lieu nhu tren:
Nell
bam
phim
'=' ta
duoc
ki^'t
qua:
67,68
+
19,381.
Tir
ket qua nay ta suy ra: RAB=
67,68Q
va Z, (^B)"
ZC(AB)=
19,38Q
(tong

cam khang nhieu hon tong dung khang la 19,38 Q).
Neu bam
phim
'shift 2 3 =' ta
duoc
ket qua:
70,4Z0,279.
Tu
ket qua nay ta suy ra: Z^B =
70,4Q
va cpAi? =
0,279
rad (Dien ap UAB som
pha hon i la
0,279
rad).
He so cong
suat
cua mach AB:
coscpAu
=
cos0,279
= 0,96. '"'
Co the
tinh
true tiep coscpAis bang may
tinh
casio
fx570es
tu ket qua:

1
+
12
200Z
^-
6
(50 + 50i)
Bam
phim
'='
Bam 'shift 21=' (de lay goc
cpAis)
Bam 'cos =' se
duoc
ket qua 0,96 (tuc la
cos(pAB=
0,96).
Vi
du 10:
(DH-2011)
Doan mach AB gom hai doan mach AM va MB mac noi
tiep.
Doan mach AM gom dien tro thuan Ri = 40 Q mac noi tiep voi tu dien
CO
dien dung C =
0,25/::
mF, doan mach MB gom dien tro thuan R2 mac noi
tiep voi cuon cam thuan. Dat vao A, B dien ap
xoay
chieu co gia tri hieu

dung
va tan so khong doi thi dien ap tuc thoi 6 hai dau doan mach AM va
• MB Ian luot la :
UAM
= 50 V2
COS(1
OOnt -
7Tr/l
2) V va
UMB
=
ISOcoslOOnt
(V).
He so cong
suat
cua doan mach AB la
A.
0,86.
B.0,84.
0.0,95.
D. 0,71.
Zr =
= 40(Q)
_UAR ("AM+^MB).
Huong
dan
\
Cty
TISmi
MTV

D
VVtl
Khang Vl^t
1
+
I^MB
"AM
-AM
-
150
5072Z
-AM
-7K
12' J
Thuc
hien cac
thao
tac bam may
tinh
[=]
bllilil
dJ EE
0,84 nghia la
coscp
« 0,84 => Chon B.
cos
x(40-40i)
duoc
ket qua
Vi

du 11: Cuon day thuan cam co he so tu cam L = 2/71 (H) mac noi tiep voi
doan mach X. Dat vao 2 dau mach mot dien ap u =
120N/2
cosl007:t
(V) thi
cuong do dong dien qua cuon day la i = 0,6 V2
cos(1007:t
- 71/6) (A). Tim hieu
dien
ap hieu dung giua 2 dau doan mach X.
A.240
V. B.120N/3V.
C.60^/2V.
D.120V.
Huong
dim
ux = u -
UL
= u -
I.ZL
=
120>y2
-
(0,6V2Z
~
30)200i
=
120^y2Z
- 60
r:>Ux

=120(V)=^ChonD.
BAi
TOAN
LIEN
QUAN
DEN
CQNG
Hl/dNG DI^N 1
VA
DIEU
KlfN
LECH
PHA
Phuangphdpgidi
^ ^
1) Dieu kien
cong
huang
Z,.Zc«Lo.~«co
= ^of =
271 VLC
OT =
27IVLC
I»U
Zz,=IZcoSLc.
=
S-i
He qua cua hien tuong:
coC
2

*
I
==>p
, =r- R=— t''«'
'iii.ix
- 'cong_luH)ng 'max R
tan
cp
= 0
=>(p
= 0 ne n u =
UR
, i: cung pha :
Vi
du 1: Cho doan mach RLC noi tiep co gia tri cac phan tu co
dinh.
Dat vao
hai dau doan mach nay mot hieu dien the
xoay
chieu co tan so thay doi. Khi
tan so goc cua dong dien bang
COQ
thi cam khang va dung khang co gia tri 20
Q va 80 Q. De trong mach xay ra cong huong, phai thay doi tan so goc cua
dong dien den gia tri
CO
bang
A.
2
COg

.
B. 0,25
COQ
.
C. 0,5
COQ.
D.
4coo.
trphtSn
thUc V$t
It
LTDII
Ht'ni hcnh VTV2, t^p 2 - Chu
VMii
isk-ri
Huong
dan
Z[
=W(,L
= 20(a) L =
20
(i)C
=
80(Q)=>C =
80Wn
De xay ra cong huang: w =
1 1
•
= 2cUn
•Chon A.

/20 I ,v. 'y. ,„
I
w,)
80o)()
Vi
du 2: Mot cuon day c6 dien tro thuan 100 (Q) va c6 do tu cam l/n (H), noi
tiep
voi tu dien c6 dien dung
SOO/TI
().iF). Dat vao hai dau doan mach mot
dien
ap xoay chieu tan so 50 (Hz). De dong dien trong mach cung pha voi
dien
ap ta phai ghep noi tiep voi tu C mot tu Ci c6 dien dung la bao nhieu?
A.
500/K (|,iF). B. 250/Tt (laF). C. 125/7t (^iF). D. 50/7t (^iF).
De (p = 0 thi Zc + , = Z,
=>
— + = coL => C, = —(i-iF) => Chon C.
Vi
du 3: Cho doan mach dien xoay chieu gom cuon day thuan cam L, tu dien C
va bien tro R mac noi tiep. Khi dat vao hai dau mach mot dien ap xoay
chieu on djnh c6 tan so'f thi thay
An^i'^hC
= 1. Khi thay doi R thi
A.
dien ap hieu dung gii>a hai dau bien tro thay doi. ,
B. tong tro cua mach van khong doi.
C. cong
suat

tieu thu tren mach thay doi. ^, ,
D.
he so cong
suat
tren mach thay doi. :i , , , ,
Hu6iig
dan
Tir
dieu kien
4TI^FLC
= 1 suy ra ZL =ZQ, tuc la trong mach xay ra cong
'U,^
= U = khong doi VR
hirang
va
liic
nay :
Z
=
7R'+(Z|
-Zef =R
^7 I -y
=> Z thay doi
P =
-
R
P thay doi
•
Chon C.
R

cos(p
=
—•
= 1 = khong doi VR
Vi
d\ 4: Doan mach xoay chieu RLC mac noi tiep, dien tro thuan cua mach
R = 50Q. Khi xay ra cong huong d tan so'fi thi cuong do dong
difn
bang
1
A.
Chi
tang tan so cua mach dien len gap doi thi cuong do hieu dung trong
mach la 0,8 A. Cam khang cua cuon day khi con 6 tan so fi la
A.25Q.
B.50Q.
C. 37,5 Q. D. 75 Q.
Huo^tg
dan -
Khi
f = f, thi Zc, = ZLJ va U = UK = IjR = 50 (V).
48
Ctr
Tiyilll
MTV
D
VVn
Khang Vi^t
j^hi
f = 2 f, thi ZL2 = 2ZL,

^50- +
2,25.Zr,
=•
7 - -
>Z|, =25(Q)
= ^
vaZ,=VR^.(Z,,-Zc,)^=^
Chon A.
«•
-,1
,),v'.<i:i.) i
hay V •
• •
0,8
Vi
du 5: ^^9* doan mach AB gom hai doan mach AM va MB mac noi tiep. Doan
mach AM gom dien tro thuan Ri mac noi tiep voi tu dien c6 dien dung C,
doan mach MB gom dien tro thuan R2 mac no'i tiep voi cuon cam thuan c6 do
tu
cam L. Dat dien ap xoay chieu u =
Uocoscat
(Uo va co khong doi) vao hai
dau
doan mach AB thi cong
sua't
tieu thu cua doan mach AB la 85 W. Khi do
LCCO^
= 1 va do lech pha giira
UAM
va

UMB
la 90". Neu dat dien ap tren vao hai
dau
doan mach MB thi doan mach nay tieu thu cong
sua't
bang: ^n^,
A.85W.
B. 135 W.
c. now.
D.
170 W.
C
A/
Dat dien ap vao AB :
Dat dien ap vao MB:
U'R.
Z,,=Zc=^P =
Huong
dan
R, +R2
U)
, 1 ' , v>J
III
-(Ijf
<
tantpAM
tancp^B =-1
-Zc ZL
= -1^ZL =RiR2
P' =

R2 =
U-R,
R; + zi
R2 +R,R2
= P = 85(W)=^Chon A.
Ri
+ R2 A
Chu y:
Neii
cho
bicii
thuc
u, ui.
hoac
uc ta dnh
dime
do
lech
pha cua u vai
UL
hoac
uc. Mat
khdc
ui.
sani
han i la KI2 va uc tre han i la
TT/I
; tie do suy ra (p.
Vi
du 6: Mot mach dien xoay chieu gom mot tu dien C noi tiep voi mot cuon

day. Dat vao hai dau doan mach mot dien ap u = U V2
coscot
(V) thi dien ap
hai
dau tu dien C la u^ = U
N/2
cos(a)t
- 7t/3) (V). Ty so gii>a dung khang va
cam khang bang - •
A.
1/3.
B.
1/2.
C.
1.
D.2.
x^^^^m
Huang
dan
Vi
I
luon luon
som han la n/2 va theo bai ra U som han UQ la n/3 nen
^ tre pha han I la 71/6, tuc la (p = -— .
6
Do do :tan(p =
Z,
-Z
^=tan—=>R
=

(Z, ZL)>/3>0.
R 6 V e L/
Dua vao bieu thuc u va uc suy ra:
UAB
=
^AB
= ^^Y
R^+(ZL
-Zcf =Zc =>2(Zc-ZL) =
Zc=>Zc=2ZL=>ChonD.
4
49