p = —y. + —y- cos 2cot. 2 2 Nhiet lucmg toa ra tran dien trd thu ^ 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 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 - 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. 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 ? n A. Dian ap trd pha hcfn cudng dp ddng difn mdt goc cp = — 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 ? -2 A. p = Ri 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. CI=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. 10 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 D6N G DAY HOC Hoat ddng cua hoc sinh Hoat ddng 1 TrO giup cua giao vi§n 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 tia : q = Cu = CUQ sin cot - Cudng dp ddng dien: i = —i = CcoUn cos cot dt " => i = IQ cos (Ot, vdi IQ = CCOUQ . 12 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 ? C 1 1 M N A B 'V Mat khae, ta ed u = UQ sin cot => u = Un cos '0 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' 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 u = Uo cos ^ n^ cot — 2 hpp vdi tnjc 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 - Mac mach dian nhu hinh ve tran bang mach : R= 5,lkO. C = 0,01^xF 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 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 nghia cua XQ ? GV nau cau hdi thia't ka' phucmg an thi nghiam - Hay thia't ka' phucmg an thi nghiam dd minh hoa cdng thiic Zp = va nau coC each tia'n hanh thi nghiam ? 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 : 16 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 TKBGVL#12/2(NC) 17 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 v2, 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' ; 18 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 ZL = coL va ehia hai vc ciia bidu thiic cho v2 bidu thflc tran dupe viet nhu tha' nao ? • - Sc) sanh bieu thiic viita xay dung vdi ; bidu thiie dinh luat 6m 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. 20 BAI28 MACH CO R, L, C MA C N6 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 D6N G DAY HOC Hoat ddng cua hoc sinh Hoat ddng 1 Trp giup ciia giao vi^n 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 22 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 UL = COLIQ cos(cot + —) = UoLCOs(cot + - ) Ur = _ ^0 71, coC 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 Bidu didn cae dien ap tran cung mpt gian dd Fre - nen ta dupe : - 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 ? 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 ? ^i + ^c O u 1 luc -- S —•• P X - Mudn tim dupe dian ap tran hai ddu A, B ta phai tim vecto nao ? 23 Tacd: U = UR+OL+U C =>U = ^Ui+(UL-Uc)^ TT ,T coL U L - Up fiir tancp= ^ *- ^^^ U R Khi coL> thi tancp>0, dian coC H^ ' - ap sdm pha hon so vdi cudng dp ddng dian. Khi coL < thi tan cp < 0, dian coC Y , . ap trd pha hon so vdi cudng dp ddng dian. vay bidu thflc cua dien ap tran hai ddu AB cd dang : u = Uv2 cos (cot + cp) Trong dd U = ^U^+(UL-UC) ^ - Xae dinh dp lach pha cua didn ap tran hai ddu A, B so vdi cudng dp ddng dian trong mach ? Tfl dd eho bidt khi mio dian ap gifla hai ddu A, B trd pha va sdm pha so vdi cudng dp ddng dian trong mach ? roL tan

UC . lo. C ULL2. D. Z = + coL] o)L2 CAu 6. Cudng dp ddng dien ludn luOn trd pha hon dien ap d hai ddu doan mach khi 29 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 nd'i tia'p la A. C = 4- - B. co= ^ VL • VLC C. C = ^^ - D. L - ^ 'Leo VcoC 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. 30 BAI29 C6N G SUXT CUA DONG DifiN XOAY CHlfiu Hfi sd C6NG SUXT I-MUCTl£U LVe'ki^n thflc - 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. 2. Vi ki n5ng - Ren luyan ki nang logic toan hpc de xay dung cac bidu thflc cua cae dai lupng vat li. - Ren luyen ki nang lam bai tap trac nghiem khach quan nhidu lya chpn. II-CHUXNBI Giao vien - Chudn bi phia'u hpc tap cho HS. Hoc sinh - HS on tap lai cdng thflc tinh cdng sudt tiau thu cua mach dien mpt chieu. Ill - THI£ T K£' HOAT D6N 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 32 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 laS^ = 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: UR 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: •y R S^ = UIcoscp = R I => coscp = — • GV nau eau hdi dd HS tim hidu y nghia cua ha sd edng sudt - Nhan xet gi ve gia tri eOa he sd cong sudt ? Khi nao he cdng sudt dat gia tri cue dai ? TKBG VLyi2/2(NC) 33 - 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. can 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. 34 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. cau 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. cau 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 = 3000 . 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 M AY PHA T DifiN XOAY CHI^U 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. II-CHUXNBI 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. 36 m - THifiT K6 HOA T DON 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 = 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 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: e = -N do dt = 27ifNo sin cot ( n e = 27rfNA cos cot — " ' 2 e = En cos ' 7t^ cot — 2 Vdi EQ = 27TfNOo la bian dp eua 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. 38 phat dien xoay chidu thudng dung va tim hidu ki hon vd nguyan tde hoat dpng cung nhu cdu tao cua may phat dien ? 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 o. Cau 3. Cach lam nao trong eac each sau day khdng tao ra dupe sudt dien dpng cam flng trong khung day ddn kin ? A. Cho khung day quay trong tfl trudng ddu. 43 B. Dat khung day trong tfl trudng deu, bdp meo khung day dd thay ddi dian tich S cua khung. C. Cho khung day chuydn dpng trong tfl trUdng ddu sao eho mat phang khung day ludn vu6ng gde vdi cac dudng sflc. D. Thay ddi cam flng tfl B eua tfl trudng ma khung day dat trong do. cau 4. Phdn cam ciia may phat dien la A. phdn chuydn dpng roto. B. phdn dflng yan stato. C. phan tao ra tfl trudng. D. nhung cupn day, trong dd xua't hien sudt dien dpng cam flng. cau 5. Cach lam nao trong cac each sau day khdng lam tang suat dian dpng cam flng cua may phat dian xoay chidu mpt pha ? A. Tang sd cupn day mdc ndi tia'p cua phdn flng. B. Tang sd cap eye cua phdn cam. C. Tang tde dp quay cua roto. D. Giam sd cap eye eua phdn cam. cau 6. Mpt may phat dien ed p cap eye. Tde dp quay cua rdto la n vdng/phut. Tdn sd bia'n thian eua sudt dian dpng cua may phat la A. f = pn. B.f = P^. 60 C. f = ^60. D. f = ^- n n cau 7. Ket ludn nao sau day sai khi so sanh may phat dian xoay chidu ba pha va may phat dien xoay chieu mpt pha ? A. Ca hai ddu boat dpng theo nguyan tde hien tupng cam img dien tfl. B. Ca hai ddu cd eau tao gdm phdn cam va phdn flng. C. Ca hai deu cd phdn cam la phdn chuyen dpng, phdn flng la phdn dflng yan. D. Ddng dien tao ra bdi hai may la ddng xoay chidu. Cau 8. Ket luan nao sau day dung khi ndi vd dien ap trong each mac hinh tam giac ? A. Ud=V3Up. B. Ud=Up. CUd=^ - D. V3Ud=Up. 44 BAI31 DONG CO KH6NG D6NG BO BA PHA I-MUCTl£U 1. \ i ki€n thflc - Hidu tha' nao la sy quay ddng bp va khdng ddng bd. - Giai thich dflpe nguyan nhan cua sy quay khdng ddng bd trong thi nghiem giao vian tia'n hanh. - Hidu th^ nao la tfl trudng quay va each tao ra tfl trudng quay nhd ddng dien xoay chidu ba pha. - Nam dupe nguyan tde cdu tao va hoat dpng cua dpng co khdng ddng bd ba pha. 2. V^' ki n3ng - Ren luyen ki nang quan sat GV tien hanh thi nghiam va rut ra ket luan. - Ren luyan ki nang tim hidu, nghian cflu thia't ka' flng dung ki thuat vat li. - Ren luyan kl nang lam cae bai tap trac nghiem khach quan nhidu lya chpn ve dpng CO khdng ddng bp ba pha. II-CHUXNBI Giao vien - Chudn bi cac thi nghiem vd sy quay ddng bp va sy quay khong ddng bp. - Chuan bi phidu hpc tap. Hoc sinh - On lai kian thflc vt ddng dien xoay chidu 3 pha. Ill - THifiT K£' HOA T D6N G DAY HOC Hoat ddng cua hpc sinh Hoat ddng 1 Kiem tra, chuan hi dieu kien xuat phat. Dat v^n de Trp giup cua giao vien GV nau cau hdi kidm tra kien thflc cu - Viet eac bidu thflc cua cac sua't dien dpng tran cac cupn day cua may phat 45 HS suy nghica nhan tim cau tra ldi HS nhan thflc dupe vdn dd cua bai hoc Hoat ddng 2 Tim hieu tiir trudng quay, sir quay ddng bp va SIJT quay khdng ddng bp HS Ihao luan ehung toan ldp - Tfl trudng do nam cham gay ra ed cae dudng sfle tfl quay trong khdng gian. HS tia'p thu, ghi nhd 46 dian xoay chidu ba pha ? Bidu didn sy phu ttiupc cua chflng vao thdi gian tran eung mdt dd thi ? Dat van di' : Dpng eo dipn xoay chidu ed hiau sudt cao hon dpng co dipn mpt chidu. Mpt im didm ldn cua ddng dien xoay chidu la tao ra dupe tfl trudng quay dung trong cae dpng co dipn xoay chidu. Vay tfl trudng quay la gi ? Tai sao loai ddng eo dien xoay chidu xet trong bai hpc nay gpi la dpng co khdng ddng bp ? GV nau eau hdi de HS tim hieu vd tfl trudng quay - Nhan xet gi vd tfl trucftig do nam cham chfl U gay ra khi eho nam cham quay quanh mpt true ? GV thdng bao - Khi mpt nam cham quay quanh mdt true, tfl trudng do nam cham gay ra cd cac dudng sflc tfl quay trong khdng gian. Dd la tfl trudng quay. HS suy nghl ca nhan, tim cau tra ldi - Kim nam cham se quay ciing tde dp gde vdi nam cham chfl U. HS thao luan ehung toan ldp va dua ra dy doan - Khung day se quay eung tde dp vdi nam cham. HS quan sat GV tidn hanh thi nghiam va rut ra ka't luan - Khung day khdng quay cflng tde dp vdi nam cham ma quay vdi tde dp gde nhd hon tde dp goc cua nam cham. GV gidi thieu thi nghiem ve sy quay ddng bp va tra ldi cau hdi - Dat mdt kim nam cham trong Idng eua nam cham chfl U, quay ddu nam cham chfl U. Nhan xet gi vd sy quay eua kim nam cham ? N GV nau cau hdi dd HS tim hieu sy quay khong ddng bp - Ndu thay kim nam cham bang mpt khung day kin ed the quay quanh mpt triic thing dflng thi hidn tupng gi xay ra khi quay deu nam cham ? N GV tia'n hanh thi nghipm, yau cdu HS quan sat va rut ra kdt luan. - GV quay nam cham cho den khi nam cham quay ddu va yau cdu HS quan sat nit ra nhan xet. 47 HS thao luan ehung toan ldp dd giai thich hian tupng. - Khi nam cham quay tao ra tfl trudng quay, tfl trudng quay lam cho tfl thong qua khung day bien thian, trong khung day xudt hien mpt ddng dien cam flng. Cung ehinh tfl trudng quay nay tac dung lan ddng dien trong khung mpt momen lye lam khung day quay. - Theo dinh luat Len-xo, khung day quay theo chidu quay cua tu trudng dd lam giam tde dp bien thian cua tfl thong. - Na'u khung day quay vdi tde dp gde bang tde dp gde cua nam cham thi tfl thdng qua khung day khong bie'n thien, ddng cam flng bang khong, khong edn mdmen lye tfl tac dung. Mdmen cam lam cho khung day quay cham lai. Luc dd lai cd ddng cam flng va mdmen luc tfl tac dung vao khung. - Vay, tde dp gde cua khung day luPn nhd hcfn tde dp goc cua tfl trudng quay. Giao vian yau cdu HS giai thich hien tupng. GV nau cac eau hdi gpi y Hien tupng gi xay ra trong khung day khi nam cham quay ? - Mdmen cua lye tac dung nao lam cho khung day quay ? - Theo dinh luat Len - xo thi khung day phai quay nhu the nao de lam giam tde do bia'n thian cua tfl thdng qua khung day ? - Neu khung day quay vdi tde d6 goc bang tde dp goc eua nam cham thi hian tupng gi xay ra trong khung day ? Tfl dd rut ra ka't luan gi ? GV the cha' hoa kieh thflc - Theo thi nghiem I, kim nam cham quay cung tde dp gde vdi tfl trudng. Ta ndi kim nam cham quay ddng bp vdi tfl trudng. - Ddi vdi thi nghiem 2, nhd cd lac dung cua tfl trudng quay va hien tupng cam ung dien tfl ma khung day quay vdi tde dp gde nhd hem tde dp gde eua tfl trudng. Ta ndi khung day quay khdng ddng bp vdi tfl trudng. Hoat ddng 3 Nghien cflu each tao ra tiir trudng quay bang dong dien ba pha HS thao ludn ehung toan ldp - Cd thd tao tfl trudng quay bing ddng dien ba pha. Mdc ba cupn day gidng vdi mang dien ba pha. Trong ba cupn day ed ba ddng dian cung bian dp, cung tdn sd nhung lach pha nhau Mdi cupn day ddu gay d vung xung quanh O mpt tfl trudng ma cam flng tfl ed phuong ndm dpc theo true cupn day va bidn ddi tudn GV nau cdu hdi vd vdn dd cdn nghian ciiii. - Tlieo cac thi nghiam tran, dd tao tfl trudng quay ta phai tac dung co hpc dd quay ddu nam cham quanh mpt true. Liau cd each nao t^o tfl trudng quay ma khdng phai tde dung co hpc nhu tran khdng? ^ GV nau cac cau hdi gpi y - Cd the sfl dung tfl trucaig cua ddng dian dd tao ra tfl trudng quay hay khdng ? Nd^u cd thi phai sfl dung ddng dian khong ddi hay ddng dien xoay chidu ? - Cd the sfl dung ddng dian ba pha dd tao ra tfl trudng quay dupe khdng ? - Neu sfl dung hp thdng ddng dien xoay chidu ba pha dd tao tfl trudng quay ta phai lam thd nao ? TKBGVLyi2/2(NC) 49 hoan vdi cung tdn sd co nhung lach pha nhau 3 B] = Bocoscot 8 2 = BQCOS cot r 2n1 B3 -BQCO S COtH Hoat ddng 4 Nghien ciiu cau tao va hoat dpng cua dpng co khdng dong bp ba pha HS thao luan ehung toan ldp - Dpng eo gdm hai bp phan chinh: Stato ed ba cupn day gidng nhau qudn tran ba loi sdt bd tri lech nhau 1/3 vdng trdn. Rdto la mpt khung day. 50 - He thdng ddng dipn xoay chidu ba pha dupe dua vao cac cupn day bd tri nhu hinh ve, hay via't bidu thflc cua tfl trudng tao bdi cac cupn day tai tam vdng trdn va bidu didn cac vecto tfl trudng gay ra bdi cac ddng dien tai thdi diem bdt ki ? - Hay chiing minh tfl trudng tdng hpp gay ra bdi he thdng ddng dian xoay chidu ba pha tai O cd dp ldn khdng ddi va quay trong mat phang song song vdi ba true cua ba cupn day vdi tde dp gde CO ? (Viec chdng minh nay diing cho HS khd, gidi) GV the che hoa kieh thflc - Vay, ed thd tao ra tfl trudng quay bang ddng dian xoay chieu ba pha. Vecto cam ling tfl tdng hpp B eua tfl trudng tdng hpp cd dp ldn khdng ddi va quay trong mat phdng song song vdi ba true cupn day vdi tde dp gde co. GV ndu cau hdi dd HS thiet ka' flng dung kl thuat dpng CO khdng ddng bp ba pha - 6 tren ehung ta da bia't nhd ed hian tupng cam flng dien tfl va tac dung cua tfl trudng quay ma khung day quay va sinh cdng. Hay thiet k^ mpt dpng co boat dpng theo nguyan tde dd.? GV nau cac eau hdi gpi y - Dpng CO gdm eac bp phan nao? Bp phan nao dflng yan ? Bd phan nao chuyen dpng ? GV thdng bao - Dpng CO hoat ddng theo nguyan tde tran la dpng eo khdng ddng bp ba pha. - Trong thuc ta', Rdto ta mpt hinh tru tao bdi nhidu la thep mdng ghep lai. Trong cac ranh xe d mat ngoai rdto cd dat eae thanh kim loai. Hai ddu mdi thanh dupe ndi vao cac vanh kim loai tao thanh mpt chia'e Idng. Ldng nay each dien vdi ldi thep va cd tac dung nhu nhidu khung day ddng true dat lach nhau. Rdto ndi tren gpi la rdto long sdc. - Khi mdg- cae cupn day d stato vdi nguda 4ian ba pha, tfl trudng quay tao thanh ed tde dd goc bang tdn sd gde cua ddng dian. Tfl trudng quay tac dung lan ddng dian cam flng trong cae khung day d rdto cac momen lye lam rdto quay vdi tde dpc nhd hem tde dp quay cua tfl trudng. Chuyen dpng quay cua rdto dupe sfl dung dd lam quay eae may khae. - Cdng sudt tiau thu eua dpng co dien ba pha bang cdng sudt tiau thu cua ba cupn day d stato cpng lai. - Hiau sudt tiau thu cua dpng eo dian ba pha bang cong sudt tiau thu cua ba cupn day d stato cpng lai. Hiau suat cua dpng CO dupe xac dinh bang ti sd gifla cdng sudt CO hpe ^ ma dpng ca sinh ra va cdng sudt tiau thu ^ eua dpng co: H = 4 51 Hoat ddng 5 Cung cd bai hpc va dinh hudng nhiem vu hpc tap tia'p theo GV yau cdu HS lam cac bai tap trdc nghieni trong phia'u hpc tap dd cung cd kiah thflc - Lam cae bai tap vd nha 1,2, 3,4 SGK. - 6n lai kia'n thflc vd sudt dian dpng cam flng, vat liau tfl. PHlfiU HOC TAP cau 1. Thi nghiam dupe bd tri nhu hinh ve. Quay nam cham chfl U quanh true quay vdi van tde gde COQ . Ket luan nao sau day dung khi ndi vd sy chuyen dpng dpng eua kim nam cham khi nam cham chfl U da quay dn dinh ? A. kim nam cham quay vdi van tde gde co > COQ. B. kim nam cham quay vdi van tde goc co = COQ. C. kim nam cham quay vdi van tde gde co co^. can 4. Phdn cam cua mpt may phat dien xoay chidu mpt pha cd 2 cap eye vd quay dupe 1200 vdng trong mot phflt. Mdt may phat didn khae ed 5 cap eye cdn phai quay dupe bao nhiau vdng trong mpt giay dd sudt dian dpng nd gay ra bang may phat didn cd hai cap eye ? A. 2 vdng. B. 4 vdng. C. 6 vdng. D. 8 vdng. Cau 5. Mpt may phat dian ba pha mdc hinh sao cd didn ap pha 127V. Ngudi ta dua ddng ba pha vao ba dian trd gidng nhau mdc hinh tam giac, mdi tai cd dien trd 100 Q. Cdng sudt tidu thu cua cac tai la A. 1452W. B. 1584W. C. 1684W. D. 1784W. 53 BAI32 MAY BrfN AP. TRUYDN TAI DifiN I-MUCTlfiU 1. Vi kid'n thflc - Phat bidu dupe tac dung cua may bia'n ap va trinh bay dupe nguyan tde hoat dpng va ca'u tao cua may bi^n ap. - Nau dupe edng dung va Ipi ich eua may bien ap, sy bien ddi dian ap va cudng dp ddng dien qua may bia'n ap. - Md ta dupe cau tao cua may bia'n dp. - Tham gia giai thieh nguyan tde hoat dpng eua may bidn ap. - Tham gia xay dung cac bidu thflc —^ = —^ ; —^ = —- • U2 N2 I2 u, 2. Vi kl ndng - Van dung kien thflc hien tupng cam flng dipn tfl, giai thich nguyen tde hoat dpng cua may bia'n ap. - Ap dung cae bidu thflc vd suat dien dpng, dinh luat 6m, cdng sudt dd thiet lap cac bidu thflc lien he gifla dien ap va cudng dp ddng dian d cac cupn so cap va thfl cap eua may bie'n ap. n-CHuiNB I Giao vien - May bia'n ap hpc sinh. - Ddng hd da nang hian sd. - Ngudn xoay chidu. - Mdu dien trd cdng sudt. - Khoa dien. - Bang lap rap. - Bp day nd'i mach. - Bang so dd truydn tai dian nang. 54 Hpc sinh - 6n lai kia'n thflc vd sudt dien dpng cam ihig, vat liau tfl. Ill - THifiT Kg HOAT D6N G DAY HOC Hoat ddng ciia hoc sinh Hoat ddng 1 Kiem tra, chu^n bi dieu kian xudt phat. Dat van de HS suy nghl ca nhan tim cau tra ldi \' HS nhan thflc dupe vdn dd cua bai hpc Hoat ddng 2 Nghien cflu ca'u tao va nguyen tac hoat dpng ciia may bie'n ap HS thao luan ehung toan ldp Trp gitip cua giao vi^n GV nau cau hdi kiem tra kiaii thflc cu - Trinh bay cdu tao va nguyan tde hoat dpng eua dpng eo khong ddng bp ba pha? Dat vdn de : May bien ap la gi ? Vi sao trong ha thdng truydn tai ddng dien xoay chidu di xa khdng thd thia'u may bien ap ? Bai hpc ngay hdm nay giup chflng ta giai dap nhflng cau hdi dd. GV nau cau hdi vd vdn dd edn nghien cflu - Cho mpt thi nghiam dupe bd tri nhu hinh ve dudi day, hai cupn day cd sd vdng day Ni,N2 dupe dat vao ldi sdt chfl U va khep kin blifg loi sdt chfl I. Na'u dat vao hai ddu cupn day N] mpt dien ap xoay chidu thi sd chi cua vdn ka V2 nhu tha' nao? So sanh sd chi eua V2 vaVi? (~>® N, N, * 55 - Ddng dian xoay chidu trong cupn day N| tao ra tfl trudng bi ^ ddi trong ldi sat, do dd tfl thdng qua ldi sat eung bien ddi theo. Tfl thdng biah ddi trong ldi sdt xuyan qua cupn day Nj se sinh ra trong cupn nay mpt sudt dian dpng cam flng va tao ra dian ap d hai ddu cupn nay. Vi vay vdnke Vj cd sd ehi khae khdng. - Sudt dian dpng ty cam tran cupn Nl: C] = -Nl — = -COCPQN] cos cot. dt Sudt dian dpng cam flng tran cupn Nj: 62 = -N2 — = -COCP0N2 cos cot dt Dodo E, _N | €2 N2 E2 N2 Mat khae, hai vdnk^ do sudt dipn dpng trdn hai cupn day nan sd chi cua chflng phu thude vdo ti sd N HS thao luan ehung toan ldp - Cdn ed hai cupn day ed sd vdng Nt,N2 dupe lap theo so dd tran. Dian dp xoay chidu mdc vdo cupn day N| Idy tfl bidn thd hpc sinh loai 12 V. 56 GV ndu cac eau hdi gpi y - Hian tupng gi xay ra ddi vdi loi sdt khi dat mpt dian ap xoay chidu vao cupn day N| ? - Tfl thdng bian thian trong ldi sdt dupe truydn qua Nj thi trong cupn ddy Nj xudt hian hian tupng gi ? - Sd chi cua hai vdnke ed quan ha nhu thd nao ddi vdi sudt dian ddng ty cam tran cupn Ni va sudt dian dpng cam irng tran cupn Nj ? - Sua't dien dpng ty cam tran cupn N; va sudt dian dpng cam iing tran cupn Nj cd quan he nhu thef nao dd'i vdi sd vdng day N„N2? GV ndu cau hdi thia't ka' phuong an thi nghiem - Hay thidt ka' phuong an thi nghiam dd kidm tra ? HS quan sat GV tiah hanh thi nghiam va rut ra kai luan - Vdn kd V2 ed sd chi khae khdng. E,. U, N, HS tidp thu, ghi nhd GV tia'n hanh thi nghiam, yau cdu HS quan sat va rut ra kdt luan. - Thi nghiam sfl dung hai cupn day cd sd vdng tucmg flng la 1200 vdng, 250 vdng. GV thdng bao - Thia't bi ehung ta vfla ldp rap dd lam thi nghiem d tren gpi la may bia'n ap. - May bia'n dp la thiet bi hoat dpng dya tran hien tupng cam flng dipn tfl, dung dd bidn ddi dian ap xoay chidu ma khdng lam thay ddi tdn sd cua nd. - May biah ap gdm hai cudn ddy cd sd vdng qudn tran mpt loi sdt kin. Ldi sdt thudng 1dm bang eac la sdt hoac thep pha silic ghep each dian vdi nhau de giam hao phi dian nang do ddng phu- cd. Cac cupn day thudng lam bang ddng va dat each dian vdi nhau vd each dipn vdi ldi sat. 57 - Mpt trong hai cupn day cua may bien ap dupe ndi vdi ngudn dian xoay chidu, dupe gpi la cupn so cdp. Cupn thfl hai dupe ndi vdi tai tiau thu dupe gpi la cupn thfl cdp. Hoat ddng 3 Nghien cflu six bie'n ddi dian ap va cudng dp ddng dien qua may bien ap GV nau cau hdi vd va'n dd cdn nghian cflu - Khi mach hd nhu thi nghiam d tran thi sd chi cua cdc vdnka' chinh la dien dp d hai ddu cua mdi cupn day va cung chinh la sudt dian dpng hiau dung d hai ddu mdi cupn day. Ndu ndi mach dien thanh mach kin thi bidu thflc —^ E2 U^^N ^ U2 N2 HS thao luan ehung toan ldp - Na'u bd qua dian trd cua day quan thi cd thd coi dien ap hiau dung d hai ddu mdi cupn day bang sudt dien dpng hiau dung tuong flng trong mdi cupn day. Do dd : U^^N ^ U2 N2 - Neu N2 > N, thi U2 > Uj: May cd tac dung tang dien ap (may tang ap). - Ndu N2 < Nl thi U2 < Ul : May cd tac dung giam dipn ap (may ha ap). 58 edn dung nfla khdng ? Khi nao thi may bien ap bia'n ddi dien ap tang? Khi nao may bien ap bien ddi dian ap giam ? GV nau eae cdu hdi gpi f - Dian dp hai ddu cupn thfl cdp va so cdp lian he vdi sudt dian dpng va cudng dp ddng dian trong mach nhu thd nao ? - Didu kian nao de ca khi mach kin thi dien ap hai ddu ngudn dien bang sudt dien dpng cua ngudn dian ? GV neu cau hdi vd va'n di cdn nghian cflu tidp HS thao luan ehung toan ldp - Ne'u coi dien nang hao phi trong niay bien ap la khong dang ke thi cdng suat d hai mach so cdp va thfl cdp la nhu nhau : ^ , = ^2hayU,I, =U2l2 L U, - Nhu vay khi may bidn dp lam dien ap tang lan bao nhiau ldn thi cudng dp ddng dian giam di bay nhiau ldn va ngupe lai. HS thao luan ehung toan ldp - Sfl dung thi nghiem d tran nhung mach thfl cap cdn phai ndi kin bang mpt tai tiau thu. Do U va I tuong flng d mach thfl cdp vd so cdp bang vdnka' va ampe kd. HS quan sat GV tidn hanh thi nghiam, Idy sd liau va xfl li sd lieu HS rut ra ket luan Na'u coi dien nang hao phi trong may bia'n dp la khdng dang kd thi cdng sudt d hai mach so cdp va thfl cdp la nhu nhau : - Khi may bien ap bidn ddi dian ap tang hoac giam thi cudng dp ddng dien se bia'n ddi nhu tha' nao ? Tim bidu thflc toan hpe bieu didn sy bia'n ddi dd ? GV nau eac eau hdi gpi y. - Na'u coi dien nang hao phi trong may bia'n dp la khdng dang kd thi cdng sudt trong hai mach so cdp va thfl cdp se the nao ? GV nau cau hdi thidt ke phuong an thi nghiem - Hay thia't ke phuong an thi nghiem kidm tra ? GV tien hanh thi nghiem, yau cdu HS quan sat, lay sd liau va xfl li sd lipu 59 ^ i = ^2hayU,I , =U2l2 => Ii_U 2 I2 Uj Hoat ddng 4 Tim hieu tac dung cua may bie'n ap ddi vdi viec truyen tai dian nang HS thao luan theo nhdm, sau dd dai dian nhdm lan bao cao ka't qua Cong sudt hao phi tran day Id : A^^RI ^ =:>AS^ = R J (U coscp) Cdch 1 : Giam dian trd R cua dudng day. Day la each lam tdn kem vi phai tang tia't dipn eua day, ' do dd tdn nhieu kim loai lam day va phai tang sfle chiu dyng cua cae cpt dian. Cdch 2 : Tang dian ap U d noi phat dian va giam dian ap d noi tidu thu dian tdi gia tri cdn thidt. Cach nay cd thd thyc hien dcm gian bang may bien ap, do dd dupe ap dung rpng rai. Hoat ddng 5 Cung cd bai hpc va djnh hudng nhiem vu hpc tap tiep theo 60 GV nau eau hdi vd vdn dd cdn nghian cihi - Tai sao khi truydn tai dian nang di xa thi dien nang thudng bi tiau hao dang kd ? Hay tim each khdc phue hian tupng tran ? GV nau cae cau hdi gpi y - Khi dian nang chay tran day ddn thi dien nang tiau hao do hian tupng gi ? - Cdng sudt hao phi do toa nhiat tran dudng day dupe xae dinh nhu tha' nao ? - Na'u gpi ^ la cdng sudt truydn di, coscp la ha sd cdng sudt cua mach difn thi cdng sudt hao phi dupe xac dinh theo 9^ va coscp nhu tha' nao ? - Dya vao edng thflc xae dinh A ^ , hay tim each khdc phuc hao phi dipn nang ? - Trong cdc each khdc phuc, each nao da thyc hian va cd tinh kinh ta' cao ? GV yau cdu HS lam cac bai tap trdc nghiam trong phidu hpc tap dd cung cd kia'n thflc - Lam cac bai tap ve nha 1, 2, 3, 4 SGK. - 6n lai cac kia'n thflc vd ddng dian xoay chidu. PHlfiu HOC TAP cau 1. May bia'n ap biah ddi dian ap xoay chidu ma khong lam thay ddi A. bian dp cua dian ap. B. gia tri hipu dung cua dian dp. C. bian dp va tdn sd cua dien ap. D. tdn sd cua dian ap. Cau 2. N^u tang sd vdng day cua cupn thfl cdp ldn hon sd vdng day eua cupn so cdp thi A. dian ap tran cudn thfl cdp tang va ldn hon dian ap trdn cupn so cdp. B. dian ap tran cupn thfl cdp giam va nhd hon dian ap tran cupn so cdp. C dian ap tran cupn thfl cap tang nhung ludn nhd hon dien ap tren cupn so cdp. D. dien dp tran cupn thfl cdp khdng thay ddi. Cau 3. Cho mpt dien dp xoay chidu vao ddu vao cua mpt may bia'n ap thi dien ap d ddu ra cd gia tri hieu dung tang gdp hai lan gia tri hieu dung cua dien ap ddu vao. Cudng dp ddng dien d ddu ra se A. tang gap hai ldn. B. giam hai ldn. C. tang bdn ldn. D. khdng thay ddi. c a u 4. Khi cha' tao may tang ap, nan dung day cua cupn thfl cdp la loai day CO dudng kinh A. to hon dudng kinh day eua cupn so cdp. B. nhd hem dudng kinh day cua cupn so cdp. C. bang dudng kinh day cua cupn so cap. D. bat kl. Cau 5. Cach lam nao trong cac each lam sau day lam giam edng sudt hao phi cua he thdng truydn tai dien ? A. tang dien ap d noi phat dien. B. giam dien ap d noi phat dien. C. tang cong sudt truydn di. D. giam cdng sua't truyen di. 61 cau 6. Ka't luan nao trong cac ket luan sau day sai khi ndi ve cdng sudt hao phi tran dudng day tai dien ? Cdng sudt hao phi A. ti la vdi chidu dai dudng day tai dien. B. ti la nghich vdi tie't dian day tai dien. C. ti la nghich vdi binh phucfng dian ap gifla hai ddu day d tram phat dian. D. ti la nghich vdi binh phucmg cdng sua't truydn di. cau 7. Dat mpt dien ap xoay chidu cd gia tri hieu dung 380V vao cupn so cdp cua mdt may tang ap. Tai cupn thfl ca'p, dien ap hiau dung la 12V va cd sd vdng day la 30vdng. Sd vdng day eua cupn so cdp Id A. 950vdng. B. 850vdng. C.750vdng. D. 700vdng. cau 8. Mpt tram phat dian truydn di mpt cdng sudt lOOkW tran day ddn eo dian trd R = 8 Q. Dien ap tfl tram phat dien la U = lOOOV Cdng sudt hao phi tran day ddn la A. 80kW. B. SOW. C. 70kW. D. 70W. 62 BAI33 BAI TAP V^ DONG DifiN XOAY CHlfiu I-MUCTlfiU 1. Ve kieh thflc - van dung eac cong thflc dd giai cac bai toan ve doan mach xoay chidu mac ndi tiep. - Bia't each ve va sfl dung gian dd Fre-nen dd giai eac bai toan vd doan mach xoay chidu mdc ndi tidp. - Lam quen vdi dang bai tap hpp den. - Bia't each lam mpt sd bai toan vd truydn tai dian nang di xa va bai toan xac dinh tfl thdng qua khung day. 2. Vi ki nSng - Ren luyan kT nang van dung cdng thflc de giai cac bai toan vd doan mach xoay chieu mdc nd'i tiep. - Ren luyen kl nang ve va van dung gian dd Fre - nen. - Ren luyan ki nang lap luan logic dd lam bai toan vd hop den. II-CHUXNBI Giao vien - Phia'u hpe tap. Hpc sinh - On lai cac kia'n thflc va ddng dien xoay chidu. Ill - THifiT Kfi' HOAT D6N G DAY HOC Hoat ddng cua hoc sinh Hoat ddng 1 Kiem tra, chuan b| dieu kien xuat phat Trp giiip cua giao vien GV neu cau hdi kiem tra kien thflc cu - Viet bidu thflc tinh tdng trd eua doan mach R, L, C mdc ndi tie'p ? Ne'u trong doan mach chi cd hai trong ba phdn tfl 63 HS suy nghl ca nhan tim cau tra ldi Hoat ddng 2 Lam bai tap 1 de ren luyen ki nang van dung cac cdng thflc cua doan mach xoay chieu va lam quen vdi bai toan tim eye tri HS lam bai tap theo nhdm, sau dd dai dian nhdm lan bao cao ka't qua 1. a) Dung khang cua tu dian la : ^ coC Tdng trd cua doan mach la : Z^^R?+ z^ «6oa. b) Bieu thflc cua cudng dp ddng dian tfle thdi trong doan mach la: i = lQCos(l007it + cp) Trong dd: Io=^«2A . Dp leeh pha eua dien ap so vdi cudng dp ddng dien dupe xac dinh: —Z n tancp = —^«-I,73=:>cpw R 3 Suy ra, cudng dp ddng dien sdm pha hon dian dp mpt gde — 64 tran thi tdng trd cua doan mach dupe xac dinh nhu tha' nao ? - Nau cac da,c didm cua sy bieii ddi dien ap va cudng dp ddng dian qua mdy bien ap ? - Khi nao doan mach dupe ndi la ed tinh cam khang ? tinh dung khang ? GV yau cdu HS lam bai tap 1 trong phia'u hpc tap theo nhdm, sau dd dai dien nhdm lan bao cao kdt qua. GV nau eac cau hdi gpi y - Bidu thflc tdng quat cua cudng dp ddng dien trong mach cd dang nhu thd nao ? - Trong bidu thflc tdng quat, dai lupng nao cdn xac dinh ? - Mudn xac dinh gia tri bien dp eiia cudng dp ddng dien ta dp dung dinh luat nao ? - Xae dinh dp leeh pha bang edng thflc nao ? Y nghia eua dp lech pha trong cdng thflc dd ? Suy ra dp lech pha cua cudng dp ddng dien so vdi dien dp ? Biau thflc cua cudng dp ddng dien la : i = 2 cos n 100m+ -1(A). 2. Cdng sua't tiau thu tran bidn trd R duoc xac dinh: o U U' R dp dung ba't dang thflc Cd-si: ( 7} 1 R + ^ R >2Zc Ddu bang xay rd khi R = ZQ « 52Q. Khi dd cdng suat dat gia tri eye dai 2Zr 69W. Hoat ddng 3 Lam bai tap 2 de k-en luyen kl ve gian dd vecto Fre - nen cho doan mach xoay chieu HS lam bai tap theo nhdm, sau dd dai dien nhdm lan bao cao kdt qua a) Cudng dp ddng dien trong mach dupe xac dinh : I=UR=i l = 0,5A. R 100 a m khang: X^=-^ = u, 100 Q. - Viet cong thflc tinh cong sudt tiau thu tran bia'n trd ? - Cong suat tiau thu tren bia'n trd cd the tinh theo dien ap va gia tri dien trd nhu the' nao ? - Dya vao bieu thflc tinh cdng sudt, hay cho bidt cdng suat dat gia tri eye dai khi nao ? - Cd the ap dung ba't ding thflc Cd si de tim gia tri eye dai eua edng sudt dupe khdng ? GV yau eau HS lam bai tap 2 trong phia'u hpc tap theo nhdm, sau dd dai dian nhdm lan bao cao ka't qua. GV nau eac cau hdi gpi y - Mudn tinh dp ty cam ciia cupn cam va dien dung cua tu dian ta phai tinh dupe dai lupng nao ? Cd the sfl dung dinh luat Om da tinh eac dai lupng dd dupe khdng ? TKBGVLyi2/2(NC) 65 =>L = -^«0,318H. CO Dung khang: Zc = — = 175 Q. =='C- 1 Si 1,82 ^F COZL b) Tdng trd cua doan mach la ; V I caC = 125 Q. Z = JR^+|COL-- ^ UAB=I Z = 62,5 V. c) Gian dd Fre - nen nhu hinh ve UAN=UR+U L UMB=UL+U C Tfl gian dd Fre - nen ta thdy UAN sdm pha hon so vdi UMB mpt gde SOQ. Vdi: SOQ = ^ + (p,. 66 - Mudn sfl dung dinh luat 6m dd tinh cam khang va dung khang cdn phai xac dinh dupe cudng dp ddng dian hiau dung qua hai phdn tfl nay ? - Hay ve gian dd Fre - nen cho doan mach ? Chu y cdn phai ve cdc dien ap theo dflng ti la ? - Dian ap U^]sj vaUj^g Id dian ap gifla cac phdn tfl nao? Cdn phai tdng hpp cac vecto dian ap nao dd cd UAN vdUMB ? - Quan sat tran gian dd Fre - nen, tfl dd cho nhan xet vd sy nhanh pha, cham pha gifla dien dp U^^ vaU^B*? Xet tam giac vudng SOP cd 0P= UOR; SP = UoL,tacd: tancpi=--^ = l=>cp, = - vay UAN sdm pha hon so vdi UMB mpt gde s5Q = ^ + ep,=^ . 2 * 4 Cung tfl gian dd Fre - nen : UAB=V(OP)'+(OQf = ^u2+(Uc-UL f = 62,5 (V). Hoat ddng 4 Lam quen vdi dang bai toan hpp den HS lam bai tap theo nhdm, sau dd dai dian nhdm ldn bao cao ket qua Tacd: i = 0,5sin| l007rt + ~ i=0,5cos 'lOOnt+^-^' 6 2 71 = 0,5cos lOOnt— |{A) GV yau cdu HS lam bai tap 3 trong phia'u hpc tap theo nhdm, sau dd dai dian nhdm lan bao cao kdt qua. GV nau cac cau hdi gpi y - Lieu rang doan mach cd the chfla hai phdn tfl la cudn cam va tu dien dupe khdng ? - Na'u doan mach cupn cam va tu dian thi dp lach pha cua cudng dp ddng dien so vdi dien ap hai ddu doan mach bang bao nhiau ? - Hay xac dinh dp lech pha gifla dien ap va cudng dp ddng dian. Tfl dd hay cho bie't doan mach cd tinh cam khang hay dung khang ? 67 Tfl bidu thflc eua u va i ta thay dian ap sdm pha hon cudng dp ddng dien mpt gde — • Doan mach cd tmh cam khang nan gdm cupn cam thudn va dien trd mdc ndi tia'p. Mat khae, ta cd Z = ^R^ + Z[ = —= 120Q R tan (0 = —^ = V3 R Giai he phuong trinh: R = 60Q, ZL=60A^=«104 Q b) Cdng sudt tiau thu cua doan mach la : 9^ = UIcoscp = 7,5W. Hoat ddng 5 Lam bai tap 4 de ren luyen each tinh tfl thdng qua mot dien tich HS lam bai tap theo nhdm, sau dd dai dian nhdm lan bao cao ka't qua Ap dung cdng thflc : 0^ = BSeosa - Tai thdi diem ban ddu t = O phap tuya'n eua khung day ed hudng vdi vecto cam img tfl nan a = O. - Tai thdi didm t, a = 27cft nan tfl thong qua mdt vdng day tai thdi diem t dupe xae dinh : cpj = BSeos27ift ^ O i =2.10'^cos207it (Wb). 68 - Tdng trd eua doan mach dupe xac dinh nhu tha' nao ? - Dp lech pha cua dien ap so vdi cudng dp ddng dian duoc xac dinh nhu the nao ? GV yau cdu HS lam bai tap 4 trong phia'u hpc tap theo nhdm, sau dd dai dian nhdm lan bao cao ka't qua. - Bidu thflc tfl thong qua mdi vdng day cd dang nhu the nao ? - Xac dinh gde a tai thdi didm t ? Sudt dien dpng cam flng tfle thdi trong khung day : dO, e = -N ^- = NBS2;rsin27ift dt z^e = 6,28sin20Kt (V). Sudt dien dpng hieu dung la : E = ^.4,4V . Vi dian trd trong cua khung day khdng dang kd nan sudt dien dpng bang dien ap dat vao hai ddu dien trd. Suy ra: Cudng dp ddng dien hieu dung E chay qua dien trd: I = — « 0,11 A. Hoat ddng 6 Lam quen vdi bai toan truyen tai dien ndng di xa HS lam bai tap theo nhdm, sau dd dai dian nhdm lan bao cao ke't qua Tacd: A9^ = Rl^ Trong dd dien trd va cudng dp ddng dien dupe xac dinh : R = p'=2,5.10- ^ ^•^•^^' -3Q. S 0,5.10-' I = = lOOA. U cos cp Cdng sua't hao phi tran day : A ^ = RI^=30W. - Dian ap dat vao hai ddu R dupe xac dinh nhu the nao ? - Neu coi dien trd cua khung day la khdng dang kd, khi ndi vdi dian trd R tao thanh mach kin thi suat dian dpng ty cam va dien dp dat vao R cd dac diem gi ? GV yau cdu HS lam bai tap 5 trong phia'u hoc tap theo nhdm, sau dd dai dien nhdm lan bao cao ket qua. - Cdng sudt hao phi tran dudng day dupe xac dinh nhu the nao ? - Mudn xac dinh dixgc cong sua't hao phi can phai xac dinh dupe nhflng dai lupng nao ? - Dien trd tran dudng day dupe xac dinh bang cdng thflc nao ? - Khi truydn tai dian cdn cd bao nhiau day din ? Mdi day ddn cd chidu dai bang bao nhiau ? - Hieu sudt truydn tai dian dupe xae dinh bang cdng thflc nao ? 69 Hiau sudt truydn tai dien la : x\ = W «94,4%. PHlfiu HOC TA P cau 1. Doan mach AB nhu hinh ve R B gdm mpt bien trd va mpt tu dian cd didn dung C = 6l,3|iF mdc ndi tidp. Dat vao hai ddu A, B mpt dien dp xoay chidu u = 120eosl007tt(V). 1. Didu chinh eho dien trd cua bien trd R, = 30Q. a) Tinh tdng trd cua toan mach. b) Via't bieu thflc eua cudng dp ddng dien tfle thdi trong doan mach. 2. Cdn didu ehinh cho dien trd cua bia'n trd den gia tri nao dd cdng sudt tran bidn trd dat eye dai ? Tinh gia tri eye dai dd. cau 2. Mdt doan mach dian AB nhu hinh ve R -nmm^ A M B N gdm mpt dien trd thudn R = 100 Q, mpt cupn cam thudn va mpt tu dien mac nd'i tiep. Bie't dian ap hieu dung gifla hai ddu dian trd, cupn cam, tu dien ldn lupt la UR = 50V ;UL = 50V ;Uc = 87,5V ; tdn sd ddng dian la 50Hz. . a) Tinh dd ty cam cua cupn cam va dien dung cua tu dian. b) Tinh tdng trd eua doan mach AB va dipn ap hiau dung U^B c) Ve gian dd Fre - nen. Can cfl vao gian dd dd: tim dp lach pha ciia dien dp gifla hai diem A va N so vdi dipn ap giua hai diem M va B; tim lai U^B 70 cau 3. Mpt doan mach chfla hai trong ba phdn tfl: tu dian, dian trd thudn, cupn cam thudn mdc ndi tidp. Bia't dien ap gifla gifla hai ddu doan mach va cudng dp ddng dipn qua nd ldn lupt cd bieu thflc: u = 60cosl00m(V)va i = 0,5sin I007lt+- (A). 6. a) Hdi trong doan mach cd cac phdn tfl nao ? Tinh dung khdng, cam khang hoac dian trd tuong flng vdi mdi phdn tfl dd. b) Tinh cdng sudt tiau thu cua doan mach. cau 4. Mpt khung ddy ddn phang gdm 50 vdng day, mdi vdng cd dipn tich 400 cm^ dat trong tfl trudng deu ed cam flng tfl bang 0,05T. Luc t = 0 phap tuyen eua khung day cd hudng vdi vecto cam flng tfl. Cho khung day quay vdi tde dp khdng ddi 600 vdng/phut. True quay cua khung vudng gde vdi cac dudng sflc tfl. a) Vidt bidu thflc cua tfl thdng qua mdi vong day theo thdi gian. b) Lap bidu thflc eua sudt dien dpng cam flng tfle thdi trong kh"ung day. Ldy 7t = 3,14. e) Ndi hai ddu khung day vdi dian trd thudn R =40Q. Dien trd khung day khdng dang ke. Tinh cudng dp ddng dian hieu dung cua ddng dien qua dien trd. cau 5. Mpt dudng day tai dien xoay chidu mpt pha den noi tiau thii ^ xa 3 km. Gia thia't day ddn lam bang nhdm cd dien trd suat p = 2,5.10 Q.mva cd tiet dien bang 0,5cm^ Dien ap va edng sudt truyen di d tram phat dien ldn lupt la U = 6 kV, ^ = 540kW. Hp sd cdng sudt cua mach dien cos cp = 0,9. Tinh edng sudt hao phi tran dudng day va hifu sudt truyen tai dien. 71 BAI34 Thuc hanh : KHAO SAT DOAN MACH XOAY CHlfiu CO R, L, C MAC N6 I TifiP I-MUCTl£ U 1, Vi kien thiic - Biet each khao sat mach dian xoay chidu RLC mdc nd'i tia'p bang thyc nghiem de hidu y nghia thyc ta' cua nhflng dai lupng co ban la trd khang, sy lech pha, hian tupng cpng hudng dien. - Dung dupe dao dpng ki dien tfl, may phat am tdn va cac dung cu do thdng thudng de lam thyc nghiem, lian he gifla cac phep do cu the vdi viec ve gian dd vecto. - Bang thyc nghiam cung cd kidn thflc vd dao dpng dian tfl, cung ed kia'n thflc vd cpng hudng trong dao dpng dien vdi dao dpng co. 2. Ve ki nang - Ren luyen ki nang phan tich lya chpn phuong an thi nghiam. - Ren luyan ki nang mdc so dd mach dian, sfl dung cac dung cu do nhu vdnkd, ampe ke... - Ren luyan ki nang sfl dung dao dpng ki dian tfl trong thyc nghiam. - Ren luyen ki nang xfl li thdng tin thu dupe khi tien haiih thi nghiem. - Ren luyan ki nang phdi hpp hanh dpng trong nhdm. II-CHUXNBI Giao vien - Chudn bi mpt bien trd, mpt tu dien cd 20|^F, mpt cupn day cd dp ty cam 0,5H, mpt may phat am tdn, mpt dao dpng ki dien tfl hai chum tia, mpt bien thd HS. - Chudn bi 4 bd thi nghiem gdm: tu dipn ed lO^iF, cupn cam 0,5H cd didn trd thudn cd 20 Q, ampe ka' xoay chidu, vdnke xoay chidu, bia'n tha' HS, ngdt dien. - Ve hinh 34.3 va 34.4 SGK tren giay khd AQ. - Ve niach dian khao sat dao dpng dien RLC ndi tia'p tran gidy khd AQ. 72 Hpc sinh - 6n lai eae kien thflc vd ddng dipn xoay chidu. - Chudn bi gidy ve dd thi. m - THifiT K£' HOAT DONG DAY HOC Hoat ddng cua hpc sinh Hoat ddng 1 Trp giup cua giao vien Kiem tra, chuan bi dieu kien xuat phat HS suy nghl ca nhan tim cau tra ldi Hoat ddng 2. Thiet ka' cac phuong an thi nghiem khao sat mach dien xoay chieu bang dao dpng ki dien tfl HS thao luan theo nhdm, sau dd dai dien nhdm lan bao cao ket qua - HS ve mach dian chi ed tu dian, chi ed cupn cam va doan mach RLC ndi tia'p trong dd cd sfl dung dao dpng ki dipn tfl va may phat am tdn. Giai thieh nguyan tde boat dpng cua mach khi tien hanh thi nghiem. GV nau cdu hdi kiem tra kia'n thflc cu ~ Viet edng thflc xae dinh : cam khang, dung khang, tdng trd eua doan mach xoay chidu RLC ndi tiep, dp lech pha gifla dien ap va cudng dp ddng dien trong mach RLC ? - Nau ddu kien dd xay ra hien tupng cpng hudng dian trong mach RLC ndi tiep ? - Nhan xet gi vd sy lach pha gifla cucmg dp ddng dian va dien ap cua doan mach chi cd tu dian, chi ed cupn cam thudn ? GV nau cau hdi thia't ke phuong an thi nghiem - Hay thia't ka' phuong an thi nghiem kiem tra dp lech pha gifla dien ap so vdi cudng dp ddng dian eua doan mach chi ed tu dien, ehi cd cupn cam va doan mach RLC ndi tiep ? GV nau cau hdi gpi y - Chung ta da sfl dung dao dpng ki dien tfl dd tia'n hanh thi nghiem d cac bai trudc. Lieu rdng cd thd tidp tuc sfl dung dao dpng ki dien tfl dd tie'n hanh thi nghiam d bai nay dupe khong ? 73 - Na'u HS khdng ve dupe, GV yau cdu va gpi y de HS giai thich nguyen tde hoat dpng cua mach dien hinh 34.3 va 34.4 SGK. - Giai thich nguyan tac hoat dpng cua mach dien RLC ndi tiep khi tia'n hanh thi nghiem {mach dien ndy duac GV vetren gidy kho AQ) HS lam viae ca nhan Hoat ddng 3 . Thie't ke cac phuong an thi nghiem khao sat mach dian xoay chieu RLC ndi tiep bang vdnke' va ampe ke' 74 - Hay ve so dd mach dian ed sfl dung dao dpng ki dian tfl di nghian cflu dp lach pha gifla dian dp va cudng dp ddng dian ddi vdi cac doan mach ndi tran ? - Vi dao dpng ki didn tfl khdng do true tia'p ddng dien nan thay vi nghian cflu ddng dian ngudi ta nghian cflu dai lupng nao ? Dai lupng dd dupe ldy is ddu tran mach dien ? - Hay giai thieh nguyan tde boat dpng cua cac so do mach dipn hinh 34.3 va 34.4? GV tia'n hanh thi nghiem theo cac budc trong bai thyc hanh, yau cdu HS quan sat va ve dd thi vao gia'y. Tfl do, suy ra gia tri bian dp va cac dp lech pha trong eac doan mach da quan sat. Lm y : Ddi vdi budc 5 cua phuang dn thi nghiem I, de quan sdt dong thdi do thi cua hai dao dpng lech pha do R, L, C thi nen ddi hai vi tri idy tin hieu tren R cho nhau. Khi do vi tri ndi dat cOa cd hai cdng Yj va Y2 d ddu mach, tin hieu d cong Yj (tin hieu lay tren R) nhU la tin hieu ddng dien, tin hieu d cong Y2 Id dien dp cua cd mach RLC. GV neu cau hdi dd HS thidt ke phuong an thi nghiem dung vdnke va ampe k^ - Khi dung dao dpng ki dien tu de nghi&J cflu doan mach RLC ndi tiep ta mdi dflng HS thao luan theo nhdm, sau dd dai dien nhdm lan bao cao ket qua - Ta sfl dung ampe ke mdc ndi tia'p vdi mach RLC de do cudng dp ddng dien hieu dung qua mach. Dung vdnke do dien ap hieu dung tran mdi phdn tfl. Can cfl vao bang sd liau ta ed thd tinh dupe : L J ' C J ' J Hoat ddng 4. Phan nhdm, tien hanh thi nghiem Cac nhdm trudng lan nhan thidt bi thi nghiem vd cho nhdm va nhan mdu bao cao thi nghiem. - Sau khi cae nhdm da tidn hanh xong ea hai phuong an thi nghiem thi lau chui, xep lai gpn gang cae dung cu thi nghiam va ban giao lai cac thia't bi thi nghiem cho GV. Hoat dong 5. Xijr li sd lieu va via't bao cao thi nghiam HS thao luan nhdm, sau dd ca nhan xfl li sd lieu va viet bao cao. lai d viec nghian cflu dinh tinh, chua cho phep ta xac dinh gia tri cua Z L. Z^va Z toan mach. Hay thidt kd mpt phuong an thi nghiem khae cho phep ta xac dinh mpt cac dinh lupng cac gia tri tran ? GV nau cac cau hdi gpi y - Mudn xac dinh cac gia tri tran ta phai xac dinh nhiing dai lupng nao? - Cd thd su dung dinh luat 6m de xac dinh ZL, Z(-va Z toan mach dupe khdng ? Na'u dupe, ta phai do nhiing gia tri nao ? Sfl dung dung cu do nao ? GV chia ldp thanh cac nhdm thi nghiam. - Trong qua trinh HS lam thi nghiam, GV di tdi tflng ban thi nghiem dd dinh hudng giup dd HS khi HS gap khd khan. Yau cdu HS xfl li sd lieu va via't bao cao thi nghiem theo mdu cd sin trong SGK. GV thu bao cao thi nghiem cua HS sau khi HS da xfl li sd lieu va via't xong bao cao thi nghiem. 75 CHWONG VL SONG ANH SANG BAI35 TAN SAC ANH SANG I-MUCTl£U 1. Ve kie'n thflc - Nam dupe hien tupng tan sdc anh sang va giai thich dupe hien tupng. - Dua ra dupe gia thuya't I dd giai thich hian tupng tan sdc anh sang va suy luan ra dupe he qua cua cac gia thuya't dd kidm tra dupe bang thyc nghiem. - Dd xudt dupe cae phuong an thi nghiam kidm tra ha qua. - Nam viing khai niam anh sang trdng, anh sang dcfn sdc. 2. Ve ki nang - Ren luyen ki nang dua ra dy doan, suy luan he qua logic eua dy doan. - Ren luyen ki nang thidt kd phucftig an thi nghiem kidm tra. - Ren luyen ki nang quan sat, rut ra ke't luan. - Ren luyen ki nang giai thich cae hien tupng vat li. II-CHUXNBI Giao vien - Chudn bi bp thi nghiem chflng minh hien tupng tan sac anh sang. Hpc sinh - On lai cac kian thflc va lang kinh. - 6n lai cac kien thflc vd anh sang trang, anh sang mau, sy phan tich anh sang trdng, sy trdn cac anh sang mau da hpc d ldp 9 THCS. 76 m - THlfiT Kg HOAT D6N G DAY HOC Hoat ddng cua hpc sinh Trd giiip cua giao vien Hoat ddng 1 Kiem tra, chu^n bi dieu kien xua't phat. Dat va'n de HS suy nghl ca nhan tim cau tra ldi HS nhan thflc dupe vdn dd eua bai hoc Hoat ddng 2 Nghien cihi hien tupng tan sac anh sang HS thao luan ehung toan ldp - Chidu anh sang mat trdi hoac anh sang cua mpt den spi dot qua mot lang kinh. - Mat HS lan bd tri thi nghiem vdi cac thiet bi cd sdn HS quan sat GV tien hanh thi nghiam va rut ra ke't luan - Ka't qua thu dupe va't sang Id quan sat tren bang khdng nhirng bi lech vd phia day cua ldng kinh so vdi tia tdi ma cdn bi taeh thanh nhidu mau. Tren man hflng thu dupe mpt dai sang nhidu mau sdc. GV neu cau hdi kiem tra kia'n thflc cii - Nau cac ngudn phat ra anh sang trdng ma cac em da hpc d ldp 9 THCS. - Nau dac didm eua tia sang di qua lang kinh. Dat vdn de : Trong nhung ngay he, khi con mua vfla tanh, tran bdu trdi ddi khi xudt hian eac vdng nhieu mau sdc vdt ngang vdm trdi. Ngudi ta thudng gpi la cdu vdng. Tai sao cd hien tupng nhu vdy? Bai hpc ngay hdm nay giup chflng ta tra ldi cau hdi dd. GV nau cau hdi vd vdn de cdn nghian cflu - Lam the nao de tao dai sang mau nhu d eau vdng trong phdng thi nghiem ? GV yeu eau HS bd tri thi nghiem - Chiing ta cd cae thiet bi thi nghiam nhu tran ban, em nao cd thd lan bd tri thi nghiem ? GV tia'n hanh thi nghiem, yau cdu HS quan sat va rut ra ket luan 77 HS tia'p thu, ghi nhd HS thao luan ehung toan ldp ~ Suy nghl, trao ddi, dya vao kinh nghiem ciia cudc sdng... dua ra dy doan: anh sang trdng gdm nhidu anh sang cd mau sdc khae nhau, eac mau nay Ipch khae nhau khi di qua lang kinh... HS thao luan nhdm - Ha qua ciia gia thuya't 1 : Ne'u lang kinh nhudm mau cho anh sang thi anh sang cd mau ba't ki khi di qua lang kinh thi cung bi tach thanh nhidu mau. 78 GV thdng bao - Hien tupng thu dupe trong thi nghiam nay gpi la hian tupng tan sac anh sang. - Dai mau sdc thu dupe gpi la quang phd anh sang do den phat ra. GV nau cau hdi vd vdn dd cdn nghian cflu tia'p - Tai sao anh sang trdng khi di qua lang kinh thi bi tach thanh nhidu mau ? GV kd chuyan lieh sfl de dua tham dy doan : Khi mdi nghian cflu hien tucfng tan sdc anh sang thi Niuton cd ldi giai thieh rang lang kinh da nhupm eac mau eho anh sang. vay, ehung ta cd hai gia thuydt: Gid thuyet I : iSng kinh da "nhupm" cac mau cho anh sang. Gid thuyet 2 : anh sang trdng gdm nhidu anh sang cd mau sdc khae nhau, cac mau nay lech khae nhau khi di qua lang kinh. GV yau cdu HS thao luan dd suy ra ha qua eua gia thuydt I cd thd kidm tra dupctrdng thi nghiam GV nau cau hdi gpi y - Na'u gia thuydt 1 la dung thi anh sang cd mpt mau di qua lang kinh se tha'nao ?