Tài liệu Thiết kế bài giảng vật lí 12 nâng cao tập 2

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- ? 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

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