Giai Taco: — = l - - = 0.75=^4 = - : ^ k = = - ^ T = - = 2h Vay chgn dap an D Cdu 11: Khi noi ve he so cong suat cosq) ciia doan mach dien xoay chieu, phat bieu nao sau day sai? A Vdi doan mach chi c6 tu dien hoac chi c6 cuon cam thuan t h i cos(p = B Vdfi doan mach chi c6 dien trof thuan t h i coscp = C Vdfi doan mach c6 R, L, C mAc noi tiep dang xay cong hLforng thi cos(p = D Vdfi doan mach gom tu dien va dien t r d thuan mac noi tiep t h i < coscp < Giai Doan mach c6 R, L, C m i c noi tiep dang xay cong hi/dng t h i scp = Vay chgn dap an C Cdu 12: Mot vat nho c6 chuyen dong la tong hgfp cua hai dao dong dieu hoa cijng phtrdng Hai dao dong c6 phiTcfng t r i n h la X , = A , coscot va x , = A , cos cot + — Goi E la cof nkng cua vat Khoi lifcfng cua vat bkng: 'A 2E B CO'/A?+A c D «^(Af+A^)- 2E co^(Af+A^)- Giai Hai dao dong vuong pha nen: A = VAf+A^ 2E E = |mco'(A^ + A ^ ) ^ m = CO (A^A^' Vay chgn dap an D Giai chi tifit 06 thi T S D H , C D MOn V4t l( 135 C&u 13: Tren mot phuang truyen song c6 hai diem M va N each 80 cm Song truyen theo chieu tir M den N vdi hxidc song la 1,6 m Coi bien dp cua song khong ddi qua trinh truyen s6ng Biet phifotng trinh s6ng t a i N la Uj^ = , c o s ^ ( t - ) (m) t h i phifcfng trinh song tai M la: A u^^ =0,08cos^(t + 4) (m) C u^, = , c o s ^ ( t - l ) Tae6: (m) U N = 0,08 cos - t - I B u^, =0,08cos^ D t'+- (m) = , c o s ^ ( t - ) (m) 71 = 0,08cos-t 71 71 U M = 0,08cos— t + - = 0,08eos- t + - 2 V 7t = 0,08cos-(t + 2) = 0,08cos = 0,08cos - t - l v2 71 = , e o s - ( t - 2) (m) Vdy chgn dap an D Cdu 14: Dat dien ap u = Uocoscot (Uo v^ co khong doi) vao hai dau doan mach xoay chieu noi tiep gom dien t r d thuan, cuon cam thuan va tu dien c6 dien dung dieu chinh difc/c Khi dung khang la 100 Q t h i cong suat tieu thu cua doan rn^ch dat ciTc dai la lOOW Khi dung khang la 200 Q t h i dien ap hieu dung giOfa hai d i u tu dipn la 100 V2 V Gia t r i cua dien tror thuan la: A lOOQ B 150Q G 160Q Cong suat tieu thu cua doan mach dat C L T C D 120Q dai: k h i mach cong Tj2 hudng ZL = Zc = 100Q; P^,, = — = lOOW => U R Uc = I.Z' = U 7R^T(Z~^^47' ^ - I O V R IOVR :.200 = 100V2 VR^+(IOO)- « 400R' - 2R' + 2.100' => R = 1OOQ Vdy chgn dap an A Giaichi tietde thi TS DH, CD M6n V9t l( 136 Cdu 15: D a t d i e n ap u = 220 V2 coslOOTtt (V) vao h a i dau doan mach gom m o t bong den day toe l o a i l l O V - SOW m^c n o i t i e p v R = 1OOQ... + - 2 V 7t = 0,08cos-(t + 2) = 0,08cos = 0,08cos - t - l v2 71 = , e o s - ( t - 2) (m) Vdy chgn dap an D Cdu 14: Dat dien ap u = Uocoscot (Uo v^ co khong doi) vao hai dau doan mach xoay chieu... VR^+(IOO)- « 400R' - 2R' + 2. 100' => R = 1OOQ Vdy chgn dap an A Giaichi tietde thi TS DH, CD M6n V9t l( 136 Cdu 15: D a t d i e n ap u = 22 0 V2 coslOOTtt (V) vao h a i dau doan mach gom m o t bong den