Thiết kế bài giảng vật lí 12 nâng cao (tập 2) phần 1

TRAN THUY HANG - HA DUYEN TUNG

THIET KE BAI GIANG
NANG CAO
TAP HA!

NHAXUATBANHANOI



TRAN

THUY H A N G -

H A DUY£N TUNG

THIET KE BAI GIANG

lAVt
NANG CAO - TAP 2

^

V-

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NHA XUAT BAN HA NOI

CHWONG V. DONG DIEN XOAY CHIEU
•

BAI26

DONG DifiN XOAY CHlfiu
MACH DifiN XOAY CHlfiu CHI CO DifiN TRO T H U A N
I-MUCTlfiU
1. Ve kie'n thiic
- Nam ducfc khai niem dong di6n xoay chi^u va di6n ap xoay chi^u. Biet each xac
dinh ,d6 l6ch pha gii5a dien ap va circfng do dong didn xoay chieu theo bi^u thiic
hoac theo do thi bi^u di6n chiing.
- Nam duoc cac dac didm cua doan mach xoay chieu chi co di£n trd thu^n.
~ Nam duoc cac gia tri hi6u dung va each tinh cong suat toa nhi6t trung binh cua
dong di6n xoay chi^u.
2. Ve ki n i n g
- Ren luyen ki nang quan sat GV tid'n hanh thi nghiem co sit dung dao d6ng ki
dien tif, tit do riit ra cac k6't luan cua bai hoc.

II-CHUXNBI
Gido vien
- Chu^n bi mo hinh may phat dien xoay chi6u va dien k6'.
- Dao d6ng ki dien tir, ngudn dien xoay chi^u hoc sinh, may phat am tan.
Hpc sinh
- On lai cac kiah thiic ve dinh luat Om va hien tucmg cam ling di6n ttr da hoc 6 ldp
11 THPT.


Ill - THI^T K f H O A T D 6 N G DAY H O C
Hoat d6ng cua hoc sinh

Hoat ddng 1
Kiem tra, chu^n b| dieu kien
xuat phat
HS suy nghl ca nhan tim cau tra Icri
- Khi tiir thong qua mat gicfi han
boi mach dien km bien doi theo
thcfi gian.

Trd giup cua giao vi#n
GV neu cau hoi kidm tra kien thiic cu
- Hi6n tuong cam utig di6n tix xay ra
khi nao ?

- Khi do, goc a bi6'n thi6n theo
th6i gian, suy ra ttr th6ng qua mat
gi6i han bcri khung day kin bia'n
thien theo thcfi gian. Vi vay trong
day xua't hi6n m6t suat difen dong
cam ling.

- Khi cho khung day quay deu trong tit
trucmg vdi t6'c do goc co nhu hmh ve
sau day, trong khung co sua't hi6n sua't
di6n dong cam ling khong ? Tai sao ?

- Quan sat tha'y kim cua dien ke
dao dong sang phai roi sang trai
m6t each tu^n hoan. Chiing to su^t
dien d6ng trong khung day bi^n
thi6n tudn hoan.

- Yeu c^u HS quan sat GV tien hanh thi
nghi6m v6i mo hinh may phat dien
xoay chieu co noi v6i dien ke G, sau do
dua ra nhan xet ve gia trj cua suat dien
d6ng cua may phat dien xoay chieu ?
GV thong bao
- Sua't diSn dong xua't hien trong khung
day bie'n doi theo thcfi gian theo dinh
luat dang sin, thucmg goi tat la sua't di6n
d6ng xoay chieu : e = EQ cos(cot + (po).

HS tiep thu, ghi nhd

- Chu ki va tSn s6' cua bien doi cua suat
di6n dong lien he vdfi tan so goc co bdi
. ,

„

271

„

CO

cac cong thuc: 1 = — , i =
CO
2n
- Sua't dien d6ng tao bdi may phat dien

xoay chieu cung co bidu thiic dang nhu
tren.


Hoat dong 2
Tim hieu dien ap xoay chieu va
dong dien xoay chieu
- Khi do, trong mach co dao d6ng
dien cudng biic vdi t^n sd ciia suat
dien d6ng do may phat di6n xoay
chieu tao ra. Giua hai dSu d o ^
mach cd m6t dien ap bi6'n thi6n theo
thdi gian theo dinh luat dang sin.

HS quan sat GV tia'n hanh thi
nghiem vdi dao dong ki dien tu
- Do thi cua didn ap tren hai d^u
mach dien cd dang hinh sin.

GV neu cau hoi dd HS tim hidu dien ap
xoay chieu
- Neu ndi hai cue cua may phdt dien
xoay chidu vdi mot doan mach ti6u thu
di6n thi dien ap giiia hai ddu doan mach
cd bidu thiic nhu tha' nao ?
GV neu cac cau hoi goi y
- Nhan xet gi vd dao dOng dian trong
mach tiau thu ?
- Lam thi nghifm nghiem nhu th6' nao
dd kidm tra ?

GV tien hanh thi nghiem va yfeu eiu HS
quan sat dd nit ra nhan xet

GV thdng bao
- Trong trudng hop t6ng quat, bidu thiic
cLia dien ap gifia hai dau doan mach
xoay chidu AB va cudng dd dong dian
qua nd cd dang :
u = UoCos(cot + (p])
i = lQCos(cot + (p2)
- Dai luong cp = cpj -cpj goi la do lach
pha cua u so vdi i.
Na'u cp > 0 thi u sdni pha so vdi i.
Neu (p < 0 thi u trd pha so vdi i.
Na'u

Hoat ddng 3
Tim hieu dien ap va cudng do
dong di^n ciia doan mach chi c6
dien trd thuan

GV nau cau hoi dd HS tim hieu dien ap
va cudng do ddng dien cua doan mach
chi cd dien trd t h u ^


-

Dat

mdt

dian

ap

xoay

chieu

HS thao luan ehung toan idp

u = UQ cos (cot) vao hai ddu doan mach

Ap dung dinh luat Om cho doan

chi cd dien trd thudn R thi cUdng dd
ddng dien trong mach cd bieu thiic nhu
tha' nao ?
GV nau cac cau hoi goi y

mach :
i = — = —^ cos cot = If, cos cot.
R
R
^

- Xet nhung khoang thdi gian rStt nhd,
dian ap va cudng dd ddng dien coi nhu
khdng ddi, cd thd ap dung dinh luat Om
cho doan mach nay duoc khdng ?

Cudng do ddng dien tren dien trd
thudn bien thian dong pha vdi dian
ap giua hai d^u dien trd va cd bian
dd xac dinh bdi: IA = —- •
0

- Nhan xet gi ve do lach pha giua dian
ap va cudng do ddng dien trong mach ?

j^

Hoat dong 4
GV nau cau hdi dd HS tim hidu ve cac
gia tri hieu dung

Tim hieu mot sd gia trj hieu
dung

- Khi cho ddng dien xoay chieu chay
qua dien trd thudn se lam cho dien trd
toa nhiet. Nhiet lucmg toa ra tran dien
trd trong khoang thdi gian t duoc xac
dinh nhu the nao ? Cudng dd ddng dian
khdng doi chay qua dien trd phai cd gia
tri bang bao nhiau dd nhiat luong toa ra
khdng doi trong ciing khoang thdi gian t ?
GV nau cac cau hdi goi y

HS thao luan ehung toan ldp

Cdng sua't toa nhidt tiic thdi dugc
xac dinh:
p = Ri^= RIQ cos^ « t
-, .
Rio 1^0
=> p = —y. + —y- cos 2cot.
2
2

- Tai thdi diem t, cdng suat toa nhiat
tren dien trd duoc xac dinh nhu the nao ?
- Cdng suat toa nhiet trung binh duoc
Nhiet lucmg toa ra tran dien trd
t h u ^ trong khoang thdi gian t la :

2

; xac dinh : p = p = RIQ COS^ cot = — - •
; Nhiet luong toa ra trong thdi gian t
; duoc xac dinh nhu tha' nao ?
1


- Khi cho ddng I kh6ng d6i chay
qua dian trd thudn thi nhiat lucmg
toa ra tran dian trd :
Q = Klh^l

= ^ .

V2
,-^

HS ti^p thu, ghi nhd

- Ndu cho cudng dd ddng dian khdng
d6i I chay qua dian trd trong cung
khoang thdi gian t sao cho nhiat lucmg
toa ra la khdng ddi thi I phai cd gi^ tri
bang bao nhiau ?
GV thdng bao
- Dai lucmg I dvtac goi 1^ cudng dd
ddng dien hiau dung ciia ddng dian
xoay chidu.
- Cudng dd ddng dian hiau dung ciia
ddng dien xoay chidu bang cudng dd
cua mdt ddng difn khdng ddi, ndu cho
hai ddng dian dd Idn lupt qua ciing mdt
dian trd trong nhttng khoang thdi gian
bang nhau du dai thi nhiat lupng toa ra
bang nhau.
- Tuong tu nhu vay, ngudi ta cung x^c
dinh dupe suSt dian ddng hiau dung cfia
mdt ngudn dian xoay chidu : E = - j ^
va dian ap hiau dung d hai ddu doan
mach xoay chieu : U = ~^'
V2 .
- Dd do dien ap hiau dung va cudng
do ddng dian hieu dung cua ddng
dien xoay chidu, ngudi ta diing vdn

k^ va ampe ke xoay chidu.

Hoat ddng 5
Bieu dian cudng do dong dien
xoay chieu va dien ap xoay chieu
b^ng vecta quay
HS thao luan ehung toan ldp

GV nau cau hdi dd HS bidu diln cudng
dd ddng dian xoay chidu va dian ap
xoay chidu bang vectcf quay
- Hay nau each bieu didn cudng dd
ddng dian i va dian ap u bang cac veclo
quay ? Nhftn x^t gi ve hai veclo I,U
cua doan mach chi cd dian trd thudn ?


- Bidu didn cudng do ddng dien i
va dien ap u bang cac vecto quay
tucfng ling I,U cd dd clai ti la vdi
cac gia tri hiau dung U, I va quay
ngupe chidu kim ddng ho quanh
gd'c O vdi tde do gde bang tan so
goc CO cua ddng dien. d thdi diem
ban ddu t = 0, chiing cd phucmg
hpp vdi true Ox mot gde bang pha
ban ddu cua dai lupng tucmg ling.
- Tran gian dd Fre-nen cho doan
mach chi cd dien trd thudn, cac
vecto quay I, U cd ciing hudng.

Hoat ddng 6
Ciing cd' bai hoc va dinh hudng
nhiem vu hoc tap tiep theo

GV yau cdu HS lam bai tap trac nghiam
trong phia'u hpc tap de cung cd bai hpc
- HS ve nha lam cac bai tap 1, 2, 3, 4
SGK.
- HS dn tap lai cac kidh thiic vd ddng
dian xoay chidu.

PHlfiU HOC TAP
caul. Cho mdt khung day dSn phang cd dien tich S quay deu vdi tde dd gde
CO quanh mdt true vudng goc vdi cac dudng siic cua mdt tii trudng ddu
cd cam ling tii B. Trong khung day se xua't hian
A. hien tupng tu cam.
B. sua't dian ddng cam ling.
C. ddng dien mot chieu.
D. sua't dian dong tu cam.


Cau 2. Cudng dp ddng dien va dien ap ciia mdt ^oan mach xoay chidu cd dang
i = IQ sin(cot + —) ; u = Ugsin(cot — ),k4 luan nao sau day diing khi ndi
3
6
vd dp lech pha ciia didn ap so vdi cudng c^ ddng dian ?
A. Dian ap trd pha hcfn cudng dp ddng difn mdt goc cp = n—
Ad

B. Dian ap sdm pha hon cudng dd ddng ^ien mdt goc cp = — •

C. Dian ap va cudng dp ddng dian ddng[)ha.
71
D. Dien ap trd pha horn cudng dp ddng 6^tn mpt goc cp = —
6
Cau 3. Cho mach dien nhu hinh ban, cap bidi
thiic nao sau day bidu didn cudng c5
ddng dien va dian ap ciia doan mach '
A. i = locos(cot-7c) ;u = UoCOs(cot + 7J).
B. i = IoCos(cjOt);u = UoCos(cot + 7t).
C. i = IoCOs(cot);u = Uosin(cot).
D. i = IQ sin(cot + —); u = UQ cos (cot).
Cau 4. Cho dong dian xoay chidu i = locoscot chay qua dien trd thudn R.
Biau thiic nao biau didn cdng sua't toa nhiat tiic thdi tran dien trd R
sau day sai ?
A. p = Ri-2
Ri;
C. p = —^cos2cot.
2

5. p = Rlocos^cot.
RIn

RI§
„ ,
-cos2a)t.

cau 5. Cho cudng dp ddng dian xoay c;pieu i = Iosino)t chay qua difn trd
thudn trong thdi gian t. Na'u chb cudng dp ddng dien khdng doi I
chay qua dian trd thudn dd trong thdi gian t thi cudng dp ddng dien
khdng ddi nhan gia tri nao trong cac gia tri sau day de nhiet lupng

toa ra tran dian trd thudn d hai trudng hpp la nhu nhau ?

9


A. I = Io.

B. I = V2lo.

C I = i D. 1 = ^ .
2
V2
Cau 6. Cho cudng dp ddng lian xoay chidu chay qua mdt doan mach la
i = 2sinl00t (A). Cudig do ddng dian hiau dung nhan gia tri nao
trong cac gia tri sau day ?
A. I = 2A.
B. I = IA.
C. I = 4A.

10

D. 1= V2A.


BAI27

MACH DifiN XOAY CHI^U CHI CO TU DifiN, CUdN CAM
I-MUCTlfiU
1. Vi ki^'n thiic
- Hidu dupe cac tac dung cua tu dian va cupn cam trong mach dian xoay chidu.

- Tim dupe bieu thiic cudng dp ddng dien qua tu dien bang li thuya't.
- Dd xudt dupe phucmg an thi nghiem vdi dao ddng ki dien tii de nghien ciiu su
bien ddi ciia cudng dp ddng dien qua mach dian cd tu dien va dien ap giiia hai ban
tu dien theo thdi gian.
- Tim dupe bieu thiic dian ap giila hai ddu cupn cam bang li thuyet.
- Di xua't dupe phucmg an thi ngiiiem vdi dao ddng ki dien td de nghian cihi su
bien ddi cua cudng dp ddng dien qua mach dien cd cupn cam va dian ap gifla hai
dau cupn cam theo thdi gian.
" Nam dupe khai niem dung khang, cam khang. Bie't each tinh dung khang, cam
khang va ve gian dd Fre-nen cho doan mach chi cd tu dien va doan mach chi cd
cupn cam.
2. \ i ki nSng
- Ren luyen ki nang dd xua't va thia't ka' thi nghiem de nghian cihi su bia'n ddi cua
cudng dp ddng dian va dian ap theo thdi gian cua doan mach chi cd tu dien va
doan mach chi cd cupn cam.
- Ren luyen ki nang quan sat giao vian tie'n hanh thi nghiem, tir dd nit ra ke't luan.
- Ren luyen ki nang ve gian dd Fre-nen cho doan mach chi cd tu dien va doan
mach chi cd cupn cam.

II-CHUXNBI
Giao vien
- Dao dong ki dian td, bang mach dian chi cd tu dian, bang mach dien chi cd cupn
cam, may phat am tdn, bia'n thd hpc sinh loai 0 - 12V.
Hoc sinh
- 6n tap lai cac kid^n thiic vd ddng dien xoay chieu.
11


Ill - THifiT Kfi HOAT D 6 N G DAY HOC
Hoat ddng cua hoc sinh

TrO giup cua giao vi§n

Hoat ddng 1
Ki^m tra, chudn b| dieu kian
xuat phat
HS suy nghl ca nhan tim cau tra ldi

HS nhan thiic dupe va'n dd cua bai
hpc

GV nau cau hdi kidm tra kien thiic cu
- Ve gian dd Fre-nen cho doan mach
chi cd dian trd thudn ? Nhan xet vd dp
lech pha cua dien ap giiia hai ddu dien
trd thudn vdi cudng dp- ddng dian qua
doan mach chi cd dian trd thudn ?
Dat vdn de : Trong mach dian xoay
chidu, ngoai dien trd thudn, ta con gap
hai loai phdn td khae la tu dien va cupn
cam. Chiing cd tac dung gi ddi vdi mach
dien nay ? Bai hoc ngay hdm nay giiip
chiing ta tra ldi cau hdi dd.

Hoat ddng 2
Nghien ciiu gia tri turc thdi cua
cudng dp ddng dian va dien ap
cua doan mach xoay chieu chi cd
tu dien. Ve gian do Pre - nen.

GV nau cau hdi vd va'n dd edn nghian
cuu
— Dat vao gifla hai ban tu dien M va N
mpt
dien
ap
xoay
chidu
u = Uosincotthi cudng dp ddng diari

HS thao luan nhdm, sau dd dai
dian nhdm lan bao cao ket qua

trong mach cd bieu thiic nhu tha' nao?
Nhan xet gi ve dp lach pha gifla
cudng dp ddng dian so vdi dian ap
gifla hai ban tu ?

- Dian tich tran ban M d thdi didm
tia:

C
1 1

M

N

q = Cu = CUQ sin cot
- Cudng dp ddng dien:

i = —i = CcoUn cos cot
"
dt
=> i = IQ cos (Ot, vdi IQ = CCOUQ .

12

A

B

'V


Mat khae, ta ed
u = UQ sin cot => u = Un
'0 cos tot —
2
vay dien ap gifla hai ban tu dian
trd pha hem so vdi cudng dp ddng
dien trong mach m5t gde —.
HS thao luan ehung toan ldp
- Cdn mpt mach dian chi ed tu
dian. Dian ap dat vao mach dian
dupe la'y d may bie'n ap hpc sinh.
Dian ap tran hai ban tu dipn dua
vao cdng CHI ciia dao dpng ki
dien td.
- Mac ndi tiep mpt dien trd vao
mach dian, dua dian ap tren hai

ddu tu dien vao edng CH2 ciia dao
dpng ki dd nghian cuu cudng dp
ddng dian trong mach.

HS chii y Idng nghe va cjuan sat

GV nau cac cau hdi gpi y
- Xac dinh dian tich tran ban M eiia tu
dian d thdi didm t ?
- Na'u quy udc chidu duong ciia ddng
dien la chieu til A tdi M thi cudng dp
ddng dian trong mach dupe xac dinh
nhu tha' nao ?
GV nau cau hdi thiat kd phucmg an thi
nghiem.
- Hay thie't ka' phuong an thi nghiam
kidm tra ke't qua chiing ta vtra tinh dupe
bang con dudng li thuyet ?
GV*nau eac cau hdi gpi y
- Dao dpng ki dian td chi do true tiep
dian ap, lam tha' nao dd do dupe cudng
dp ddng dien trong mach ?
- Ta da biet cudng dp ddng dien qua
dien trd thudn ddng pha vdi dian ap tran
hai ddu dien trd, lieu rang cd thd mac
mpt dien trd thudn nd'i tie'p vdi tu dien
va dua dien ap cua dien trd vao dao
dpng kf dien tit thay cho viae nghian
ciiu cudng dp ddng dian trong mach
dupe khdng ?

GV tia'n hanh lap rap va gidi thieu thi
nghiem ma HS viia thia't ka'
VS^

l"^

•-Mpp^

13


HS quan sat va riit ra ka^t luan

- Mac mach dian nhu hinh ve tran bang

- Cudng dp ddng dien qua tu dipn

mach : R= 5,lkO. C = 0,01^xF

bia'n thien sdm pha so vdi dian ap

GV yau cau HS quan sat dd thi ciia dien
ap va cudng dp ddng dian trong mach

71

gifla hai ban tu dien mpt gde —

tren man hinh dao dpng ki dian tii, sau
dd riit ra ket luan vd dp lach pha gifla

dien ap va cudng dp ddng dien.

HS lam viec ca nhan, sau dd thao
luan ehung toan ldp

GV yau cau HS ve gian dd Fre-nen cho
doan mach ehi ed tu didn

- Tai thdi didm t = 0, ve vecta
quay I bidu didn cudng dp ddng
dian i = IQ eos cot hpp vdi true Ox
mpt gde bang 0, vecto quay U^ ;
bidu

didn

dien

ap

^
n^
u = Uo cos cot — hpp vdi tnjc
2
TT

Ox mpt gde —
O

U,

Hoat ddng 3
xay dung bieu thiic dinh luat
6 m ddi vdi doan mach cd tu
dien. Tim hieu khai niem dung
khang.
HS thao luan ehung toan ldp.

14

GV nau cau hdi vd vdn dd cdn nghian
ciiu
-

Dai luong

trong cong thiic
coC
IQ = CCOUQ ed y nghia gi ?


- Chia bidu thiie cho N/2, ta dupe :

Zc gifl vai trd nhu dien trd ddi vdi
ddng dian khdng ddi.

GV nau cac cau hdi gpi y
- Dat Zc = —V- va chia hai v^ ciia bidu
foC
thiic cho ^/2 bidu thiie tran dupe via't

nhu the nao ?
- So sanh bieu thiie viia xay dung vdi
bidu thirc dinh luat Cm cho doan mach
chi cd dien trd thudn, tfl dd cho biai y
nghia cua XQ ?

HS thao luan theo nhdm, sau dd
dai dian nhdm lan bao cao ket qua
- Sii dung thi nghiam vdi dao ddng
ki dian tii nhu d tran. Ldn lupt thay
ddi gia tri dien cua tu dian va tdn
sd cua dian ap dat vao hai ddu
doan mach. Quan sat su bien ddi
cua cudng dp ddng dian trong
mach tren man hinh dao dpng ki
dian tii.

GV nau cau hdi thia't ka' phucmg an thi
nghiam
- Hay thia't ka' phucmg an thi nghiam dd

HS quan sdt GV ti^n hanh thi
nghiem, tii dd rut ra nhan xet.
- Khi gia tri dipn dung ciia tu dipn
tang thi gia tri bian dp ciia cudng
dp ddng dien tran man hinh dao
dpng ki dian tii tang. Didu dd
chiing to dung khang ciia mach
giam. Suy ra dung khang ti la
nghich vdi dian dung ciia tu dian.

- Khi gia tri tang tdn sd ciia dien
ap dat vao hai ddu tu dien thi gia
tri bian dp ciia cudng dp ddng dien
tran man hinh dao ddng ki dien tii
tang. Didu dd chiing td dung khang

GV ti^n hanh thi nghiam, yau cdu HS
quan sat va nit ra kdt luan
- Tang gi^ tri dian dung ciia tu dian,
yau cdu HS hay nhan xet su phu thupc
cua dung khang vao dian dung ciia tu
dian?
- Tang gia tri tdn sd ciia dian ap dat vko
hai ddu tu dien bang may phat am tdn,
yau cdu HS hay nhan xet su phu thupc
cua dung khang vao tdn sd goc co ?

minh hoa cdng thiic Zp =

va nau
coC

each tia'n hanh thi nghiam ?

15


ciia mach giam. Suy ra dun'g khang
ti la nghich vdi tdn so cua dien ap
hay ti le nghich vdi tdn sd gde eiia

dian ap dat vao hai ddu tu dien.
Hoat ddng 4
Nghien cihi gia tri turc thdi ciia
cudng dp ddng dien va dien ap
trong doan mach xoay chieu chi
cd cupn cam. Ve gian do Fre nen
HS thao luan theo nhdm, sau dd
dai dien nhdm lan bao cab kdt qua

GV nau cau hdi vd vdn dd cdn nghian
ciiu
- Gia sit tai thdi diem t cudng dp ddng
dien xoay chieu i^locoscot chay qua
doan mach ehi ed cupn cam cd dp tu
cam L theo chidu tii A den B, hay tim
bidu thiic cua dian ap tran hai ddu cupn
cam ?
L

—nmm^—
-^-^
A B

Khi cd ddng dien bidn thian theo
thdi gian chay qua cupn day thi
trong cupn day xua't hien sudt dian
ddng cam ling:
e = - L — ^coLIrtSincot
dt
^

Quy udc chidu ddng didn chay tir
A tdi B la chieu duong. Dien ap
gifla hai diem A va B la:
u = iRAB-e
Vi cupn day thudn cam nan R^g cd
gia tri bang khdng. Nan :
16

GV nau cac cau hdi gpi y
- Hian tupng gi xay ra khi ed ddng dian
bia'n thian chay qua cupn cam?
- Sudt dien dpng tu cam tran cupn cam
dupe xac dinh nhu tha' nao?
- Theo dinh luat Om, dien ap tran hai
ddu cupn cam dupe xac dinh nhu tha'
nao?
- Nhan xet gi vd dp lech pha giiia dien
ap tran hai ddu cupn cam vdi cudng dd
ddng dien chay qua cupn cam ?


u = - e = -coLlQsincot
=:>U = UoCOS eot + —
vdi UQ =COLIO.

Cudng do ddng dian qua cupn cam
thudn cam bien thian dieu hoa vdi
7U

Cling tan sd nhimg tra pha hon —

ddi vdi dian ap gifla hai ddu cupn
cam.
HS thao luan ehung toan ldp
- Cdn mdt mach dien chi cd cupn
cam. Dian ap dat vao mach dien
dupe la'y d may bia'n ap hpc sinh.
Dian ap gifla hai ddu cupn cam
dupe dua vao cdng CHI cua dao
dpng ki dian t^.

GV nau cau hdi thi^t k^ phucmg ap thi
nghiem
- Hay thia't k€ phuong an thi nghiem va
trinh bay each tien hanh tiii nghiem dd
kidm tra k^t luan d tran ?

- Mac ndi tidp mot dien trd vao
mach dian, dua didn ap tran hai
ddu tu dien vao cdng CH2 ciia dao
ddng ki dd nghian ciiu cudng dp
ddng dien trong mach.
GV tia'n hanh lap rap va gidi thieu thi
nghiem ma HS viia thiet ka'
- Thi nghiam cdn cd: R = 5,lkQ,
cupn day L : 3000 vdng (ed loi sdl).
HS quan sat GV tie'n hanh thi
nghiam va nit ra ka't luan
- Quan sat tran man hinh dao dpng
ki dien tii ta thdy ka't luan tim dupe
bang con dudng li thuyet d tran la

hoan toan diing.

TKBGVL#12/2(NC)

GV tia'n hanh thi nghiam, yau cdu HS
quan sat va rut ra kat luan

17


HS thao luan ehung toan ldp

GV yau cdu HS ve gian dd Fre-nen eho
doan mach chi ed cupn cam

T

X

h

h

0

\
:
I

Tran gian dd vecto Fre - nen cho |

doan mach chi cd cupn cam thudn, [
—
n
'
U lap vdi I mpt gde — theo ;
chidu duong.

'•

Hoat ddng 5
Xky
Om
cam
cam

dung bieu thiic dinh lu$t ;
ddi vdi doan mach co cupn :
thu^n. Tim hieu khai niem i
khang

HS thao luan ehung toan ldp

GV nau eau hdi vd vaii dd cdn nghian cihi.
UQ

Dai lupng

coL trong cdng thflc

= COLIQ ed y nghia gi ?

\

- Chia bidu thiie eho v 2 , ta dupe \

GV nau cac cau hdi gpi y

I

- Dat Z L = coL va ehia hai vc ciia bidu

u
^L

:

i
1

ZL gifl vai trd nhu didn trd ddi vdi ;
ddng dien Ichdng ddi.

:

thiic cho v 2 bidu thflc tran dupe viet
nhu tha' nao ?
• - Sc) sanh bieu thiic viita xay dung vdi
; bidu thiie dinh luat 6 m eho doan mach
• chi cd dien trd thudn, tfl dd cho biet y
; nghia cua ?

HS thao luan theo nhdm, sau dd i i GV nau cau hdi thiet ka' phuang an thi
dai dian nhdm lan bao cao ket qua ; ; nghiam
- Sii dung thi nghiem vdi dao dpng i : - Hay thia't ke phuong an thi nghiem dd
ki dien tir nhu d tran. Lan lupt thay • : minh hoa cdng thiic ZL = coL va nau
ddi gia tri L cua cupn cam va tdn sd' ; '. each tia'n hanh thi nghiem ?

18


cua dian ap dat vao hai ddu doan
mach. Quan sat su bia'n ddi ciia
cudng dp ddng dien trong mach
tran man hinh dao dpng ki dian tii.
HS quan sat GV tia'n hanh thi
nghiam, tfl dd nit ra nhan xet.

GV tia'n hanh thi nghidm, yau cdu HS
quan sat va riit ra ket luan

- Khi gia tri L ciia cupn cam tang
thi gia. tri bian dp ciia cudng dp
ddng dien tren man hinh dao dpng
ki dian tir giam. Didu dd ehiing td
cam khang cua mach giam. Suy ra
diing khang ti le thuan vdi dp tu
cam cua cupn cam.

- Tang gia tri L eiia cupn cam bang
each cho tham ldi sat vao cupn cam, yau

cdu HS hay nhan xet su phu thupc cua
cam khang vao dp tu cam L eiia cupn
cam ?

- Khi gia tri tang tdn sd eiia dian
ap dat vao hai ddu cupn cam thi
gia tri bian dp ciia cudng dp ddng
dien tran man hinh dao dpng ki
dian tu giam. Didu dd chiing td
cam khang cua mach giam. Suy ra
dung khang ti le nghich vdi tan sd
cua dien ap hay ti le nghich vdi tdn
sd gde ciia dien ap dat vao hai ddu
cupn cam.

- Tang gia tri tdn sd eua dian ap dat vao
hai ddu cupn cam bang may phat am
tdn, yau cdu HS hay nhan xet su phu
thupc cua cam khang vao tdn sd gde co ?

Hoat ddng 6
Ciing cd bai hpc va dinh hudng
nhiem vu hpc tap tiep theo
GV yau cdu HS lam bai tap trdc nghiem
trong phia'u hpc tap dd cung cd bai hpc
- HS vd nha lam cac bai tap 1, 2, 3, 4, 5,
6 SGK.
- HS dn tap lai eac kia'n thirc vd ddng
dian xoay chieu.

19


PHlfiu HOC T ^ P
C&u 1. Cho mach dian nhu hinh ve, k^t luan
nao sau day la diing khi ndi vd sd chi
cua ampe ke trong mach dian ?

|

C
U"

A. La gia tri eiia cudng dp ddng dian
hieu dung
B. La gia tri bian dp eiia cudng dp
ddng dien

u

C. La gia tri tiic thdi cua cudng dp ddng dien
D. Ampe ka' chi sd 0 vi tu dipn khdng cho ddng didn chay qua
CAu 2. Dat vao hai ban cua tu dipn mdt dien ap xoay chidu u^Upsincot,
cudng dp ddng dien chay qua tu dien la
A. i = CUQCOs(cot).

' , n
B. i = coCUoCos cot+—
V
2

C. i = coCUosin(cot).

D. i^coCUpsin cot + — .

CAu 3. Tang tdn sd gde eua dien ap dat vao tu dien ga'p 2 ldn thi dung khang
cua tu dien se
A. tang ga'p 2 ldn.

B. giam 2 Idn.

C. tang gap 4 ldn.

D. khdng thay ddi.

CAu 4. Ngudi ta dat mpt mach dipn trong mpt hdp kin cd hai ddu day ndi ra
ngoai. Bia't rang mach dien chi sir dung mpt trong 3 linh kian didn trd
thudn R, tu dien C, cupn cam L thudn cam hoac gdm 2 trong 3 linh
kian tren mdc ndi tiep. Bang thuc nghiem tha'y rang cudng dp ddng
dien trong mach ciing pha vdi diari ap dat vao hai ddu mach dian.
Mach dian dMqc cdu tao bdi

20

A. R mdc ndi tia'p vdi C.

B. L mac ndi tia'p vdi C.

C. chi cd L.

D. chi cd R.


BAI28

MACH CO R, L, C M A C N 6 I TifiP. CdNG HUONG DifiN
I-MUCTl£u
1. \ i kid'n thtic
- Biet each ve va dung gian dd Fre - nen dd nghian ciiu doan mach ed R, L, C mdc
ndi tidp.
~ xay dung dupe eae edng thflc tinh tdng trd Z, d6 Itch pha giua dian ap va cudng
dp ddng dian, bidu thflc dinh luat 6m. Ap dung cae cdng thflc dd dd lam mpt sd
bai tap don gian.
- Nam dupe hien tucmg cpng hudng dian va didu kidn dd xay ra hian tupng cdng
hudng dien.
- Dd xua't va thia't ka' dupe phuong an thi nghipm nghian cflu hien tupng cpng
hudng dian.
2. Ve ki ndng
- Ren luyan ki nang dd xudt va thia't k^ thi nghiam dd nghian cflu hidn tupng cpng
hudng dian.
- Ren luypn ki nang quan sat giao vian tien hanh thi nghiem, tfl dd rut ra ket luan.
- Ren luyan ki nang ve gian dd Fre - nen cho doan mach R, L, C mac ndi tidp.
II-CHUXNBI
Giao vien
- Dao dpng ki dian tfl, bang mach dipn ehi ed tu didn, bang mach dian ehi cd cupn
cam, may phat am tdn, bi^n tha' hpc sinh loai 0 - 12 V.
- Chudn bi phia'u hpc tap eho HS.
Hoc sinh
- On tap lai cac kian thuc va doan mach xoay chidu chi ed didn trd, ehi cd tu dian,
chi cd cupn cam thudn.

- Phucmg phap gian dd Fre - nen.
71


Ill - THifiT Kfi HOAT D 6 N G DAY HOC
Hoat ddng cua hoc sinh

Trp giup ciia giao vi^n

Hoat ddng 1
Kiem tra, chuan b| dieu kien
xua't phat. Dat van de
HS suy nghl ca nhan tim cau tra ldi

HS nhan thflc dupe van de cua bai
hpc

GV nau cau hdi kidm tra kia'n thflc cu
- Vie't bieu thflc dian ap ciia doan mach
chi cd dien trd thudn, chi ed cupn cam,
ehi ed tu dien ? Nhan xet gi vd dp lach
pha eua cac dian ap so vdi cudng dp
ddng dian chay trong mach ?
Dat va'n dd : Doan mach xoay chidu ed
ca ba loai phan tfl (dien trd, cupn cam, ;
tu dian) mdc ndi tie'p cd mpt sd dac tinh
khae vdi doan mach dien xoay chieu chi
cd mpt loai phdn tu. Khi ta tang ddn
mpt thdng sd nao dd eua mach, ching
han nhu dien dung cua tu dien, cudng

dp ddng dian cd thd tang rdi giam. Bai
hpc ngay horn nay diing phucmg phap
gian dd Fre - nen de nghian cuu doan
mach R, L, C mac ndi tiep.

Hoat ddng 2
Nghien ciiu doan mach R, L, C
mac ndi tiep
HS chu y Idng nghe

GV gidi thieu doan mach R, L, C mdc
ndi tia'p.
- Doan mach gdm mpt dian trd thudn R,
mpt cupn cam thudn cd dp tu cam L va
•mpt dien dung C mac ndi tia'p. Ta gpi
doan mach dd la mach RLC ndi tia'p.
R

^A

L

L

1—•—'
M 75?R5OTr^—•-A
N 1

c
B#

GV nau eau hdi ve vdn dd cdn nghian
cflu
22


- Dat vao hai ddu A, B cua doan mach
mpt dien ap xoay chidu u ed tdn sd
gde CO. Hien tupng gi xay ra trong doan
mach ? Gia sfl cudng dp ddng didn chay
trong doan mach cd bieu thflc
i = IQ COS cot thi bidu thflc cua dian ap d
hai ddu doan mach cd dang nhu the nao ?

HS thao luan ehung toan ldp

- Trong mach cd dao dpng dien
cudng bfle vdi tdn sd gde bang tdn
sd gde cua dien ap.
- Bidu thflc cua dian ap tfle thdi
tran cac phdn tfl R, L, C eua doan
mach RLC hdi tia'p la
Up = u^^^ =IoRcoscot = UoCOSCot
UL

= COLIQ cos(cot + —)

71,

_ ^0

coC

- Hien tupng gi xay ra trong doan mach ?
- Vidt bidu thflc eua dian ap tran cac
phdn tu cua doan mach RLC ?
- Cac phdn tfl trong mach dupe mdc nhu
tha' nao ? Dian ap tfle thdi hai dau doan
mach cd quan ha nhu thd' nao vdi dian
ap tran mdi phdn tfl cua doan mach ?

= UoLCOs(cot + - )
Ur =

GV neu cac cau hdi gpi y

cos(cot—)
71.

= Uoccos(cot--)
Vi cac phdn tfl trong mach mdc
nd'i tie'p nan dien ap tfle thdi gifla
hai ddu doan AB la
U = U,t+UL+Uc

- Sfl dung phuang phap nao dd tim bidu
thflc tdng quat eua dien ap tran hai ddu
doan mach ? Cd thd su dung phucmg
phap gian dd Fre - nen dupe khdng ?
- Hay bidu didn dien ap tren mdi phdn

tu tren ciing mpt gian dd Fre - nen ?

Bidu didn cae dien ap tran cung
mpt gian dd Fre - nen ta dupe :

u
^i + ^c
O

1

luc

-- S
—••
P

X

- Mudn tim dupe dian ap tran hai ddu
A, B ta phai tim vecto nao ?
23