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

R R ^ 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 j ^ Hoat dong 4 Tim hieu mot sd gia trj

TRAN THUY HANG - HA DUYEN TUNG

THIET KE BAI GIANG

NANG CAO

TAP HA!

N H A X U A T B A N H A N O I

TRAN THUY H A N G - H A DUY£N TUNG

THIET KE BAI GIANG

CHWONG V DONG DIEN XOAY CHIEU

•

BAI26

DONG DifiN XOAY CHlfiu

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 Trd giup cua giao vi#n

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

- 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

- 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

HS tiep thu, ghi nhd

GV neu cau hoi kidm tra kien thiic cu

- Hi6n tuong cam utig di6n tix xay ra

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)

- 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

Hoat ddng 3

Tim hieu dien ap va cudng do

dong di^n ciia doan mach chi c6

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 <p = 0 thi u dong pha vdi i '

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 ^

HS thao luan ehung toan idp

Ap dung dinh luat Om cho doan

mach :

i = — = —^ cos cot = If, cos cot

R R ^

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 j ^

Hoat dong 4

Tim hieu mot sd gia trj hieu

dung

HS thao luan ehung toan ldp

Cdng sua't toa nhidt tiic thdi dugc

Nhiet lucmg toa ra tran dien trd

t h u ^ trong khoang thdi gian t la :

2

- Dat mdt dian ap xoay chieu

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

- 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 ?

- Nhan xet gi ve do lach pha giua dian

ap va cudng do ddng dien trong mach ?

GV nau cau hdi dd HS tim hidu ve cac gia tri 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

- Tai thdi diem t, cdng suat toa nhiat tren dien trd duoc xac dinh nhu the nao ?

- Cdng suat toa nhiet trung binh duoc

; 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

c a u l 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

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 ?

c a u 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 = ^

V2 2

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 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

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

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

HS thao luan nhdm, sau dd dai

dian nhdm lan bao cao ket qua

- Dian tich tran ban M d thdi didm

=> i = IQ cos (Ot, vdi IQ = CCOUQ

TrO giup cua giao vi§n

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

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 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 ?

Mat khae, ta ed

u = UQ sin cot => u = Un cos '0 tot —

2

v a y 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'

V S ^ l"^

•-Mpp^

13

HS quan sat va riit ra ka^t luan

- Cudng dp ddng dien qua tu dipn

bia'n thien sdm pha so vdi dian ap

71

gifla hai ban tu dien mpt gde —

HS lam viec ca nhan, sau dd thao

luan ehung toan ldp

- 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

GV yau cau HS quan sat dd thi ciia dien

ap va cudng dp ddng dian trong mach 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

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

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

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

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

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 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

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 ?

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

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 :

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

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^

- 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

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

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 ?

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)

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

HS thao luan ehung toan ldp

T X \

h h I

0 :

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 dung bieu thiic dinh lu$t ;

Om ddi vdi doan mach co cupn :

cam thu^n Tim hieu khai niem i

cam khang

HS thao luan ehung toan ldp \

- Chia bidu thiie eho v 2 , ta dupe \

I u : i

^L 1

ZL gifl vai trd nhu didn trd ddi vdi ;

ddng dien Ichdng ddi :

HS thao luan theo nhdm, sau dd i

dai dian nhdm lan bao cao ket qua ;

- Sii dung thi nghiem vdi dao dpng i

ki dien tir nhu d tran Lan lupt thay •

ddi gia tri L cua cupn cam va tdn sd' ;

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

GV nau eau hdi vd vaii dd cdn nghian cihi

- Dai lupng coL trong cdng thflc

UQ = COLIQ ed y nghia gi ?

GV nau cac cau hdi gpi y

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

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 ?

i GV nau cau hdi thiet ka' phuang an thi

; nghiam : - Hay thia't ke phuong an thi nghiem dd : minh hoa cdng thiic ZL = coL va nau

' each tia'n hanh thi nghiem ?

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

- 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

- 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

Hoat ddng 6

Ciing cd bai hpc va dinh hudng

nhiem vu hpc tap tiep theo

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

- 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 ?

- 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 ?

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 C

nao sau day la diing khi ndi vd sd chi | U"

cua ampe ke trong mach dian ?

A La gia tri eiia cudng dp ddng dian

hieu dung

B La gia tri bian dp eiia cudng dp u ddng dien

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) B i = coCUoCos ' , n 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

A R mdc ndi tia'p vdi C B L mac ndi tia'p vdi C

C chi cd L D chi cd R

~ 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

I I - C H U X N B I

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

Ill - THifiT Kfi HOAT D 6 N G DAY HOC

Hoat ddng cua hoc sinh

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

Hoat ddng 2

Nghien ciiu doan mach R, L, C

mac ndi tiep

HS chu y Idng nghe

Trp giup ciia giao vi^n

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

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 L c

^ L 1—•—'75?R5OTr^—•-A 1 # A M N B

GV nau eau hdi ve vdn dd cdn nghian cflu

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

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 + U L + U c

Bidu didn cae dien ap tran cung

mpt gian dd Fre - nen ta dupe :

^i + ^c

O

u

1 luc

i = IQ COS cot thi bidu thflc cua dian ap d hai ddu doan mach cd dang nhu the nao ?

GV neu cac cau hdi gpi y

- 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 ?

- 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 ?

- Mudn tim dupe dian ap tran hai ddu

A, B ta phai tim vecto nao ?

23

- Tim bidu thflc dinh luat 6m cho doan mach RLC ndi tia'p ?

HS tia'p thu, ghi nhd

GV thdng bao

Dat Z = j R ^ + ( c o L — —

coC

, gpi la tdng trd cua mach RLC ndi tia'p

Bidu thflc cua dinh luat 6m khi dd dupe

HS thao luan ehung toan ldp

- Cudng dp ddng dian phii thupc

vao R, L, C va co

- Tfl bidu thflc dinh luat 6m, ta

thdy khi coL = 0, thi cudng

coC

dp ddng dian trong mach dat gia

tri cue dai I^ax = — Khi dd,

R

cudng d6 ddng dian cue dai chi

phu thude vao dipn trd thudn R

ciia doan mach

ndi tidjp Dien ap dat vao mach

dien dupe la'y d may phat am tdn

Dian ap tran hai ddu doan mach

dua vao cdng CHI ciia dao dpng ki

GV nau cau hdi thia't ka' phuong an thi nghiem

- Hay diiat ka' phucmg an thi nghiam kidm tra ke't luan tran ?

25

- Mac ndi tia'p mpt dien trd vao

mach dien, dua dian ap tran hai

ddu tu dien vao cdng CH2 eua dao

dpng ki dd nghian cflu cudng dp

ddng dian trong mach

- Ldn lupt thay ddi gia tri R cua

dian trd, L eua cupn cam, C cua tu

dien va tdn sd cua dien ap dat vao

hai ddu doan mach Quan sat su

bia'n ddi eua cudng dp ddng dien

trong mach tr6n man hinh dao

dpng ki dian tfl, quan sat dp lech

pha cua cudng dp ddng dian va

dien ap khi cudng dp ddng dian

cue dai, quan sat su phu thupc cua

cudng dp ddng dien cue dai vao R

khi R thay ddi

HS quan sat GV tia'n hanh thi

nghiem va nit ra ket luan

- Khi L thay ddi, cudng dp ddng

dien trong mach thay ddi Khi

cudng dp ddng dian trong mach

dat gia trj cue dai thi nd ddng pha

vdi dien ap tran hai ddu doan mach

GV gidi thiau thiai bi thi- nghiem va tidn

hanh thi nghiem, yeu cdu HS quan sit

va nit ra ka't luan

- Thi nghiem thay ddi L

- Tfl tfl dich ehuydn ldi sdt dd thay ddi dp tu cam L eua cupn day, quan sat su thay ddi cua do thi ddng dien tran man dao dpng ki dien tfl, xae dinh vi tri eua ldi sat dd xay ra cpng

- Thay ddi R, gia tri cue dai cua

dong dien thay ddi ti le nghich

vdiR

- Khi C thay ddi, cudng dp cidng

dian trong mach thay ddi Khi

cudng dp ddng dien trong mach

dat gia tri cue dai thi nd ddng pha

vdi dian ap tran hai ddu doan mach

- Thay ddi R, gia tri cue dai cua

ddng dian thay ddi ti le nghich

vdiR

- Khi f thay ddi, cudng dp ddng

dian trong mach thay ddi Khi

cudng dp ddng dien trong mach

dat gia tri cue dai thi nd ddng pha

vdi dien ap tran hai ddu doan

mach

- Thay ddi R, gia tri cue dai ciia

ddng dian thay ddi ti le nghich

vdiR,

HS tia'p thu, ghi nhd

hudng cua mach, chflng td su cue dai eua ddng dian va su ddng pha eua nd vdi dien ap ?

- Thay ddi R, quan sat su phu thude ciia cudng dp ddng dien cue dai vao R ?

- Thi nghiam thay ddi C

- Thay ddi dian dung C cua tu dien, quan sat su thay ddi cua dd thi ddng dian va dien ap tran man dao dpng ki dien tfl, xac dinh vi tri epng hudng ciia mach, chflng td su cue dai eua ddng dien trong mach va sy ddng pha ciia nd so vdi dian ap ?

- Thay ddi R va quan sat sy phu thupc eua cudng dp ddng dian eye dai

v a o R ?

- Thi nghiam thay ddi f

- Thay ddi tdn sd cua dien ap tfl may phat am tdn dua vao mach, quan sat

sy thay ddi cua dd thi ddng dian va dien ap tren man dao dpng ki dien tu, xac dinh vi tri epng hudng cua mach, chflng td sy eye dai cua ddng dian trong mach va sy ddng pha eua nd so vdi dien ap

- Thay ddi R va quan sat sy phu thupc ciia cudng dp ddng dian eye dai vao R

Hoat ddng 4

Ciing cd' bai hpc va djnh hudng

nhiem vu hpc tSp tie'p theo

^max = ~' gpi la hian tupng epng

R hudng dien

GV yau cdu HS lam cac bai tap trong

phia'u hpc tap de cung c6 bai hpc

- HS lam bai tap vd nha 1, 2, 3, 4 SGK

- HS 6n tap lai edng thflc tinh cong sudt tiau thu ciia mach dian mpt chidu

PHifiu HOC T^P

Cau 1 Quan sat tran gian do Fre - nen, ban

Anh rut ra cac ket luan dudi day Theo

em ka't luan nao dung ?

c a u 2 Dipn ap tran hai ddu doan mach R, L,

C mdc ndi tia'p va cudng dp ddng dien

chay trong mach dupe bieu didn tran

gian dd Fre ~ nen nhu hinh ban Ket

luan nao sau day la dung khi ndi ve

dian ap tran hai ddu cupn cam va dien

ap trdn hai ddu tu dien ?

A U L = U C B U L > U C

C U L < U C D U L = U C = 0

Cau 3 Neu doan mach xoay chidu chi ed L va C mdc ndi tiep thi tdng trd cua

doan mach se bang

A doan mach chi ed cupn cam C

B doan mach cd R va C mdc ndi tia'p

C doan mach cd L va C mdc nd'i tia'p

D doan mach cd R va L mac ndi tia'p

CAu 7, Khi cd hian tupng epng hudng xay ra trong mach R, L, C mdc ndi tiep

thi ka't luan nao trong cac ket luan sau day sai ?

A Cudng dp ddng dien hieu dung trong mach dat gia tri ldn nha't

B Dien ap tfle thdi d hai ddu doan mach cung pha vdi dian ap tfle thdi

d hai ddu dien trd R

C Dien ap hieu dung d hai dau dien trd nhd hon dien ap hieu dung d hai ddu doan mach

D Cam khang va dung khang cua mach bang nhau

Can 8 Didu kien de xay ra hien tupng epng hudng trong mach R, L, C mdc

Cau 9 Trong mpt hop kin cd chfla mpt mach dien gdm hai phan tfl mdc ndi

tia'p Khi dat vao hai ddu doan mach mpt dien ap xoay chidu cd gia trj hieu dung la lOOV thi dien ap hipu dung gifla hai ddu phdn tfl 1 la

100N/2V, giua hai dau phdn tfl 2 la 200V Hai phdn tfl 1 va 2 tucmg flng la

A tu dien va cupn day khdng thudn cam

B tu dien va cupn day thudn cam

C dien trd thudn va tu dien

D dien trd thudn va cupn day

- Nam dupe dac diem cua cdng suat tfle thdi, cong suat trung binh

- Nam dupe khai niam ha sd edng sudt va y nghia eiia nd

- Biet each ap dung cae cong thflc dd lani mpt bai tap trdc nghiem khach quan nhieu lya chpn

- HS on tap lai cdng thflc tinh cdng sudt tiau thu cua mach dien mpt chieu

Ill - T H I £ T K£' HOAT D 6 N G DAY HOC

Hoat ddng cua hoc sinh

Hoat dong 1

Kiem tra, chuan hi dieu kien

xuat phat

HS suy nghl ca nhan tim cau tra ldi

Trp giup cua giao vi§n

GV neu cau hdi kidm tra kie'n thflc cu

- Xae dinh cdng sudt tiau thu cua mpt doan mach ed dian ap hai ddu doan mach la U va cudng dp ddng dian mpt chieu chay qua doan mach la I ?

31

HS nhan thflc dupe vdn dd cua bai

hpc

Hoat ddng 2

Tim hieu cdng suat tiic thdi va

cong suA't trung binh

HS thao luan ehung toan ldp

Ta ed p = ui

= Uoloeoscot.eos(cot + cp)

=> p = UI2.eoscot.cos(cot + cp)

- UI cos cp + UI cos (2cot + cp)

HS tiep thu, ghi nhd

Dat vdn de : Ddi vdi doan inach mpt

chidu, na^u dung ampe kd^ do cudng dp ddng dipn I va vdnk^ do dipn ap U gifla hai ddu mpt doan mach, ta xac dinh dupe cdng sudt tiau thu dian cua doan

mach theo cdng thflc ^ = UI Ddi vdi

cac doan mach xoay chidu ndi ehung, neu chi dung vdnkd va ampe k^ de thuc hian hai phep do U va do I, ta chua thd xae dinh dupe edng sua't tiau thu dien cua doan mach Vi sao lai cd sy khae nhau dd? Bai hpc ngay hdm nay giup ehung ta tra ldi cAu hdi dd

GV nau eau hdi dd HS tim hidu edng sudt tfle thdi

- Cdng sudt tfle thdi la cdng sudt tiau thu dian eua mach dipn d mdi thdi didm

va dupe xac dinh bang p = ui Nd^u mpt doan mach cd ddng didn i = locoso)t

va dien ap hai ddu doan mach

u = UoCOs(a)t + cp) thi cdng sudt tfle thdi dupe xac dinh bang bidu thflc nao?

GV thong bao

- Cdng sudt trung binh cua ddng dian tinh trong khoang thdi gian t la dai lupng xae dinh bang cdng thflc

W

^ = Trong dd W la dian nang da tiau thu tran doan mach trong khoang thdi gian t

- Cdng sudt trung binh cua ddng dien trong mpt chu ki gpi tat la cdng sudt cua ddng dian xoay chieu Cdng suat cua ddng dien xoay chidu trong doan mach

l a S ^ = UIeoscp

Hoat ddng 3

Tim hieu y nghia cua he sd cdng

sua't

HS thao luan ehung toan Idp

- Dya vao gian dd Fre-nen cua

doan mach RLC nd'i tia'p, ta ed:

U R R

coscp = — ^ = —

• U Z

HS tia'p thu, ghi nhd

HS thao luan ehung toan ldp

- He sd cong sudt cd gia tri tfl 0

ddnl

GV nau cau hdi dd HS xay dung bidu

thflc tinh ha sd edng sudt

- Dai lupng coscp trong bidu thflc tinh cong suat cua ddng dien xoay chidu gpi

la ha sd cdng suat Hay xac dinh he sd cdng sudt dd ?

GV th6ng bao

- Ngoai each sfl dung gian dd Fre - nen,

ta cd thd xac dinh he sd cdng sudt bang

lap iuan sau; Doi vdi doan mach RLC

ndi tia'p, dien nang chi tiau thu tran dien trd thudn R Vay cdng suat cua ddng dian xoay chidti bang edng sudt toa nhiet tran R Suy ra:

- He sd cdng suat dat gia tri eye

dai coscp - 1 khi trong doan mach

xay ra hian tupng cpng hudng

dien

Ucoscp

sudt giam thi cudng dp ddng dian

trong mach phai tang dd cdng sudt

tiau thu khdng thay ddi Khi dd

hao phi vi nhiat tran day ddn se

ldn Dd la dieu nan tranh

Hoat ddng 4

Cung cd' bai hpc va dinh hudng

nhiem vu hpc tap tie'p theo

— Nhan xet gi vd su hao phi dian nang tran day ddn khi he sd cdng sudt giam Bie't rang cdng sudt tieu thii tran doan mach va dipn ap hai ddu doan mach khdng thay ddi ?

GV yau cdu HS lam cac bai tap trdc nghiam trong phia'u hpe tap dd eung cd kien thflc

- Lam cac bai tap vd nha 1, 2, 3,4 SGK

— 6 n lai khai nipm tfl thdng va dinh luat cam flng dian tfl d ldp 11 THFT; cac kien thflc ve ddng dien xoay chidu va may phat dian xoay chidu d ldp 9 THCS

PHlfiu HOC T^P

Cau 1 Ket luan nao sau day la dung khi ndi vd cdng sudt tfle thdi cua ddng

dian xoay chidu ?

A Cdng sua't tfle thdi luon la mpt hang sd

B Cdng suat tfle thdi bien thidn didu hoa theo thdi gian

C Cdng sudt tfle thdi bi^n thien tuy^n tinh theo thdi gian

D Cdng su^t tfle thdi bien thian theo quy luat ham sd mu

c a n 2 Ndu trong doan mach xoay chieu cd ddng dian I = I,2cosl007rt(A) thi

cdng sua't tfle thdi bien thian didu hoa vdi tdn sd

A 50Hz B lOOHz

C 150Hz D 200Hz

c a u 3 Ha so cdng sudt dat gia tri ldn nhdt khi

A trong mach xay ra hian tupng epng hudng dien

B tdn sd cua dien ap dat vao hai ddu doan mach dat gia tri ldn nhdt

C tdn sd cua dian ap dat vao hai dau doan mach dat gia tri nhd nhdt

D nhiat lupng toa ra trong mach nhd nhdt

c a u 4 Ha sd cdng sua't cua ddng dian xoay chidu nao trong cac doan mach

dudi day ed gia tri bang 0 ?

A Mach dien chi cd dien trd thudn

B Mach dien ehi ed cupn cam thudn

C Mach dien gdm dian trd thudn va tu dien mac ndi tiep

D Mach dien gdm dian trd thudn va cupn cam thudn mdc ndi tiep

c a u 5 Ka't luan nao sau day dung khi ndi vd sy anh hudng cua he sd cdng

sudt dd'i vdi sy hao phi dian khi truydn tai dian nang di xa ?

A Ha sd cdng sudt cang ldn thi hao phi dian nang cang ldn

B He so cdng suat cang ldn thi hao phi dien nang cang nhd

C Ha sd cdng sudt cang ldn thi hao phi dian nang khdng thay ddi

D Sy tang hoac giam eua hp sd cdng sudt khdng anh hudng den sy hao phi dian nang

c a u 6 Dat mpt dien ap xoay chidu u = 220V2 sin(lOOcot) (V) vao hai ddu

doan mach R, L, C khdng phan nhanh ed dien trd thudn R = lOOfi Khi ha sd cdng sudt cua doan mach ldn nhdt thi cdng sudt tiau thu eua doan mach la

A 284W B 384W

C 484W D 584W

cau 7 Mpt tu dian ed dian dung C = 5,3pF mdc ndi ti^p vdi dian trd R = 3 0 0 0

Doan mach dupe dat vao mang dien xoay chidu 220V - 50Hz Hp sd cdng sudt cua doan mach la

A coscp«0,147 B coscp« 0,247

C coscp « 0,347 D coscp a; 0,447

35

BAI30

I - MUC TifiU

1 \ i kie'n thflc

- Hieu dupe nguyan tde hoat dpng eua may phat dien xoay chidu

- Nam dupe cdu tao cua may phat dian xoay chidu mpt pha va ba pha

- Bia't van dung cac cdng thflc dd tinh tdn sd va sudt dien dpng cua may phat dian xoay chidu

2 Ve ki nang

- Ren luyen ki nang dn luyan kien thflc cu

- Ren luyan ki nang md ta va nau nguyan tde hoat dpng cua cae flng dung ki thuat vat li

- Ren luyen ki nang lam eae bai tap trie nghiam khach quan nhidu lua chpn ve may phat dien

I I - C H U X N B I

Giao vien

- Mo hinh may phat dien xoay chidu 1 pha va eae hinh ve may phat dian xoay

chidu 1 pha va 3 pha

- Ve hinh 30.1; 30.2; 30.4 SGK tran gidy khd AQ

- Phia'u hpc tap

Hoc sinh

- 6n lai khai niem tfl thdng va dinh luat cam flng dian tfl d ldp 11 THPT; cac kidii

thflc ve ddng dien xoay chidu va may phat dien xoay chidu d ldp 9 THCS

m - THifiT K6 H O A T D O N G DAY HOC

Hoat ddng cua hoc sinh Trp giiip cua giao vi^n

Hoat ddng 1

Kidm tra, chuin bi dieu kian

xu^t phat Dat van de

HS suy nghl ca nhan tim cau tra ldi

- Khi cd sy bien ddi tfl thdng qua

mat gidi han bdi mpt mach kin thi

trong mach xudt hien mpt ddng

dian cam flng

- Tfl cdng thflc <I> = BSeosa, suy

ra cac each lam bien ddi tfl thdng

la: lam thay ddi cam ling tfl B, lam

thay ddi dien tich S eua khung day,

lam thay ddi gde a

- Do ldn cua sudt dian dpng cam

flng trong mach kin ti la vdi tde dp

bia'n thian cua tfl thdng qua mach

e, = -N

At

- Khi AT -> 0 thi sudt dien ddng

cam flng dupe xae dinh

e^ = - N

' dt

- May phat dian xoay chidu ed hai

bp phan chinh la nam cham va

cupn day ddn Mpt trong hai bp

phan dd dflng ydn gpi la stato, bp

phan cdn lai la rdto

GV nau cau hdi kidm tra kien thflc cu

- Trinh bay hipn tupng cam flng dien tfl ?

- Trinh bay cac each lam bien ddi tfl thdng qua mat gidi han eua khung day ?

- Phat bidu dinh luat Fa-ra- day vd cam flng dien tfl ?

- Khi AT -> 0 thi sudt dien dpng cam flng dupe xac djnh nhu the nao ?

- Nau cdu tao va hoat dpng cua may phat dien xoay chidu da dupe hpe d ldp 9THCS?

Dat vdn de : May phat dien la eac thia't

bi dung de bien ddi co nang thanh dien nang Trong bai nay, ta xet hai loai may

37

HS nhan thflc dupe vdn de cua bai

hoc

phat dien xoay chidu thudng dung va tim hidu ki hon vd nguyan tde hoat dpng cung nhu cdu tao cua may phat dien ?

Hoat ddng 2

Tim hieu nguyen tac hoat dpng

cua may phat dien xoay chieu

HS thao luan ehung toan ldp

- Nguyan tde hoat dpng cua may

phat dian xoay chidu dya tran hian

tupng cam ling dien tfl Khi tfl

thdng qua mpt vdng day bia'n thian

didu hoa, trong vdng day xudt hian

mpt sudt dian ddng cam flng xoay

chidu

- Suat dien dpng xoay chieu trong

cupn day la:

sudt dian dpng cam flng

- Cd hai each dd lam cho tfl thdng

bidn thian qua cac vdng day trong

may phat dien:

+ De tfl trudng cd dinh, cho eae

vdng day quay trong tfl trudng

+ De tfl trudng quay, cae vdng day

dat CO dinh trong tfl trudng quay dd

GV nau cau hdi dd HS tim hidu nguyan tde hoat dpng cua may phdt dien xoay chidu

- Hay nau nguyan tde boat dpng cua may phat dian xoay chidu? Ndu tfl thdng qua mdi vdng day kin bien thian

<!)] =BScoscotthi sudt dien dpng cam ihig trong khung day N vdng dupe xac dinh nhu tha' nao ?

- Trong cae may phat dien, ngudi ta thudng lam tha' nao dd cd tfl thdng bidn thian qua cac vdng ddy ?