Phần 2 công suất hệ số công suất

IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn PHN 2: CễNG SUT, H S CễNG SUT I Lí THUYT Cụng Sut Mch in Xoay Chiu 1.1) Biu thc ca cụng sut Cho mch in xoay chiu cú biu thc in ỏp v dũng in u Uo cos t u V U 2cos t u V i Io cos t i A I 2cos t i A Cụng sut ca mch c cho bi P = U.I.cos, vi = u i l lch pha ca u v i 1.2) in nng tiờu th ca mch in in nng tiờu th ca mch in l W = P.t, vi t l thi gian dũng in chy mch, H S Cụng Sut 2.1) Khỏi nim h s cụng sut i lng cos cụng thc tớnh cụng sut P = UIcos c gi l h s cụng sut ca mch in xoay chiu 2.2) Cụng thc tớnh h s cụng sut UL P a) Theo khỏi nim h s cụng sut ta cú cos UI ULC U U R b) Theo gin ta cú cos= R U Z I 2.3) Biu thc tớnh cụng sut mch cú R O UR U2 U cos2 U P RI R UI cos R R R Z UC 2.4) Lu ý: Nhiu tớnh cos qua biu thc sau s thun tin hn: tan Z ZC U0L U0C U L UC , tan L cos R U0R UR 2.5) H s cụng sut, cụng sut ca mch RLC xy cng hng in: Khi cng hng in xy thỡ u v i cựng pha, vỡ vy cos ; Mt khỏc: U = UR P UI U2 R II BI TP DNG Bi Tp C Bn V Cụng Sut, H S Cụng Sut Cõu 1: Vi l lch pha ca u v i i lng no sau õy c gi l h s cụng sut ca mch in xoay chiu? A sin B cos C tan D cot Cõu 2: Cụng sut ca mt on mch xoay chiu c tớnh bng cụng thc no di õy ? A P = U.I B P = Z.I2 C P = Z.I2.cos D P = R.I.cos Cõu 3(C - 2012): t in ỏp u = U0cos(t + ) vo hai u on mch gm in tr thun R v cun cm thun cú t cm L mc ni tip H s cụng sut ca on mch l R L L R A B C D R L R2 (L)2 R2 (L)2 Cõu 4: Trong on mch in khụng phõn nhỏnh gm in tr thun R v t in C, mc vo in ỏp xoay chiu u = Uocos(t) V H s cụng sut ca on mch l [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn A R R C B R C R C R D R 2 C Cõu 5: Trong on mch in xoay chiu khụng phõn nhỏnh RLC, t vo hai u on mch in ỏp xoay chiu cú biu thc u = Uocos(t) V H s cụng sut ca mch l R R A B 2 R2 L2 2 R L C C C R R C L R C 2 D L C R )V vo hai u on mch mc ni tip gm in tr 12 cun cm v t in thỡ cng dũng in qua mch l i I0 cos(100t )A H s cụng sut ca on 12 mch bng: A 0,50 B 0,87 C 1,00 D 0,71 Cõu 7: on mch ni tip gm cun cm thun v in tr t vo hai u on mch mt hiu in th xoay chiu u U0 cos(t ) (V) thỡ hiu in th hai u cun cm l uL U0L cos(t ) (V) H s 6 cụng sut ca mch bng Cõu (H - 2013): t in ỏp u U0 cos(100t B 0,5 C 0,25 D 2 Cõu (C-2013): Khi cú mt dũng in xoay chiu chy qua cun dõy cú in tr thun 50 thỡ h s cụng sut ca cun dõy bng 0,8 Cm khỏng ca cun dõy ú bng A 45,5 B 91,0 C 37,5 D 75,0 A Cõu (C-2011): t in ỏp u = 150 cos100t (V) vo hai u on mch gm in tr thun, cun cm thun v t in mc ni tip thỡ in ỏp hiu dng gia hai u in tr thun l 150 V H s cụng sut ca on mch l 3 B C D 2 Cõu 10 (C-2013) : Mt on mch in xoay chiu gm in tr thun mc ni tip vi t in Bit in ỏphiu dng gia hai u t in bng mt na in ỏp hiu dng hai u on mch H s cụng sut ca on mch bng A 0,87 B 0,92 C 0,50 D 0,71 A Cõu 11 (C - 2011 ): t in ỏp u 150 2cos100t (V) vo hai u on mch gm in tr thun, cun cm thun v t in mc ni tip thỡ in ỏp hiu dng gia hai u in tr thun l 150 V H s cụng sut ca mch l 3 B C D 2 Cõu 12: Mt on mch gm mt in tr thun mc ni tip vi mt t in Bit h s cụng sut ca on mch l 0,5 T s gia dung khỏng v in tr R l 1 A B C D Cõu 13: Trong mch in xoay chiu RLC mc ni tip, cun dõy thun cm cú hiu in th hiu dng UR = 120V; UL = 50V; UC = 100V thỡ h s cụng sut ca mch l A [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn B 0,85 C D 0,92 2 Cõu 14: Mt mch in xoay chiu RLC t vo hai u on mch in ỏp xoay chiu cú tn s v in ỏp hiu dng U khụng i Bit in ỏp hiu dng gia cỏc phn t cú mi liờn h U = UC = 2UL H s cụng sut ca mch in l A B C D 0,5 2 Cõu 15: t vo hai u on mch RLC khụng phõn nhỏnh mt in ỏp xoay chiu u = U0cos(t) V Kớ hiu UR, UL, UC tng ng l in ỏp hiu dng hai u in tr thun R, cun dõy thun cm (cm thun) L v t in C Nu UR = 0,5UL = UC thỡ h s cụng sut ca mch l A A B C D D Cõu 16: t vo hai u on mch RLC khụng phõn nhỏnh mt in ỏp xoay chiu u = Uocos(t) V Kớ hiu UR, UL, UC tng ng l in ỏp hiu dng hai u in tr thun R, cun dõy thun cm (cm thun) L v t in C Khi A U R 2U L U C thỡ h s cụng sut ca mch l B C Cõu 17: Cho mch in RLC in ỏp t vo hai u on mch cú dng u U cos t V ; R2 L Cho C bit in ỏp hiu dng U RL U RC H s cụng sut ca on mch cú giỏ tr l A 13 B 13 C 13 D 13 Cõu 18: Cho mch in RLC in ỏp t vo hai u on mch cú dng u U cos t V ; R2 L Cho C bit in ỏp hiu dng URL 3U RC H s cụng sut ca on mch cú giỏ tr l A B C D Cõu 19: t in ỏp xoay chiu u = U cost (V) vo hai u on mch LRC mc ni tip (cun dõy thun cm) Ta thy i chm pha hn u, ULR = mch bng U v uLR sm pha hn u l /6 H s cụng sut ca on A / B / C / D / Cõu 20: Cho an mch cú in tr R, cun dõy thun cm L v t in C mc ni tip Bit in ỏp hiu dng gia hai u cỏc phn t trờn ln lt l 40 V, 80 V, 50 V H s cụng sut ca on mch A 0,8 B 0,6 C 0,25 D 0,71 Cõu 21: t in ỏp u 200cos100t (V) vo hai u mt on mch gm in tr thun R, cun cm thun L v t in C mc ni tip Dũng in mch cú cng l i 4cos(100t ) (A) Giỏ tr ca R bng A 50 B 50 C 25 D 25 Cõu 22: Mch in xoay chiu RLC mc ni tip ang cú tớnh cm khỏng, tng tn s ca dũng in xoay chiu thỡ h s cụng sut ca mch A khụng thay i B tng C gim D bng Cõu 23 Mch in xoay chiu RLC mc ni tip ang cú tớnh dung khỏng, tng tn s ca dũng in xoay chiu thỡ h s cụng sut ca mch A khụng thay i B tng C gim D bng [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn Cõu 24(C- 2012): t in ỏp u = U0cos(t + ) (U0 khụng i, tn s gúc thay i c) vo hai u on mch gm in tr thun, cun cm thun v t in mc ni tip iu chnh = thỡ on mch cú tớnh cm khỏng, cng dũng in hiu dng v h s cụng sut ca on mch ln lt l I1 v k1 Sau ú, tng tn s gúc n giỏ tr = thỡ cng dũng in hiu dng v h s cụng sut ca on mch ln lt l I2 v k2 Khi ú ta cú A I2 > I1 v k2 > k1 B I2 > I1 v k2 < k1 C I2 < I1 v k2 < k1 D I2 < I1 v k2 > k1 Cõu 25: t vo hai u on mch xoay chiu RLC ni tip hiu in th xoay chiu u 120 cos100t(V) thỡ cng dũng in mch i cos(100t )(A) in tr R ca mch bng A 20 B 20 C 40 D 20 Cõu 26 (C- 2008): Dũng in cú dng i = sin100t (A) chy qua cun dõy cú in tr thun 10 v h s t cm L Cụng sut tiờu th trờn cun dõy l A 10 W B W C W D W Cõu 27: t vo hai u mt on mch in xoay chiu mt in ỏp u = 100cos(100t) V thỡ cng dũng in qua on mch l i = 2cos(100t + /3) A Cụng sut tiờu th on mch ny l A P 100 W B P = 50 W C P 50 W D P = 100 W Cõu 28 (H2008): t vo hai u on mch in RLC khụng phõn nhỏnh mt hiu in th u 220 cos t (V) thỡ cng dũng in qua on mch cú biu thc l i 2 cos t (A) Cụng sut tiờu th ca on mch ny l A 440W B 220 W C 440 W D.220W Cõu 29 (C-2009): t in ỏp u 100cos(t ) (V) vo hai u on mch cú in tr thun, cun cm thun v t in mc ni tip thỡ dũng in qua mch l i 2cos(t ) (A) Cụng sut tiờu th ca on mch l A 100 W B 50 W C 50 W D 100 W Cõu 30: t in ỏp u = 120sin(100t + /3) (V) vo hai u mt on mch thỡ dũng in mch cú biu thc i = 4cos(100t +/6) (A) Cụng sut tiờu th ca on mch l A 240 W B 120W C 240W D 120 W Cõu 31: Mch in xoay chiu gm in tr R = 100 , cun dõy thun cm cú cm khỏng bng 100 , t 104 (F) mc ni tip t vo hai u mch iờn mt in ỏp xoay chiu u = 200cos(100t) V Cụng sut tiờu th bi on mch ny cú giỏ tr A P = 200 W B P = 400 W C P = 100 W D P = 50 W Cõu 32: t in ỏp xoay chiu cú giỏ tr hiu dng 50 V vo hai u on mch mc ni tip gm in tr thun 10 v cun cm thun Bit in ỏp hiu dng hai u cun cm thun l 30 V Cụng sut tiờu th on mch bng A 120 W B 320 W C 240 W D 160 W in cú in dung C Cõu 33: on mch AB gm in tr R 80 , t in C L 2.104 F v cun dõy thun cm cú t cm 1,1 H mc ni tip t vo hai u on mch AB in ỏp xoay chiu u 200cos 100t V Cụng sut tiờu th trờn on mch AB l A 200 W B 120 W C 100 W [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] D 160 W Trang Thy Ngc H Vin Vt Lớ - hocmai.vn IN XOAY CHIU Cõu 34 (C-2009): t in ỏp u 100 cos t (V), cú thay i c vo hai u on mch gm in 25 104 H v t in cú in dung F mc ni tip Cụng sut 36 tiờu th ca on mch l 50 W Giỏ tr ca l A 150 rad/s B 50 rad/s C 100 rad/s D 120 rad/s tr thun 200 , cun cm thun cú t cm Cõu 35(C - 2012): t in ỏp u U o cos t (V) vo hai u on mch gm in tr thun, cun cm thun v t in mc ni tip Bit cng dũng in mch cú biu thc i cos(t ) (A) v cụng sut tiờu th ca on mch bng 150 W Giỏ tr U0 bng A 100 V B 100 V C 120 V D 100 V Cõu 36: Cho on mch RC cú R = 15 Khi cho dũng in xoay chiu i = Iocos(100t) A qua mch thỡ in ỏp hiu dng hai u mch AB l U AB 50V, U C U R Cụng sut ca mch in l A 60 W B 80 W C 100 W D 120 W Cõu 37: t in ỏp xoay chiu u 120 2cos 100t V vo hai u on mch gm cun dõy thun 103 F mc ni tip.Bit in ỏp hiu dng trờn cun dõy L v trờn t in C bng v bng mt na trờn R Cụng sut tiờu th trờn on mch ú bng A 720 W B 360 W C 240 W D 360 W cm L,mt in tr R v mt t in cú C 0,6 104 (H),C (F), f 50(Hz) in ỏp hiu dng hai u on mch U = 80 V Nu cụng sut tiờu th ca mch l 80 W thỡ giỏ tr in tr R cú giỏ tr l A R = 40 B R = 80 C R = 20 D R = 30 Cõu 38: Mch in R, L, C mc ni tip cú L Cõu 39 (H 2007): t hiu in th u = 100 sin 100t(V) vo hai u on mch RLC khụng phõn nhỏnh vi C, R cú ln khụng i v L = 1/ H Khi ú hiu in th hiu dng hai u mi phn t R, L v C cú ln nh Cụng sut tiờu th ca on mch l A 100 W B 200 W C 250 W D 350 W Cõu 40 (C-2011): t in ỏp u= 220 cos100t(V) vo hai u on mch gm mt búng ốn dõy túc loi 110V 50W mc ni tip vi mt t in cú in dung C thay i c iu chnh C ốn sỏng bỡnh thng lch pha gia cng dũng in v in ỏp hai u on mch lỳc ny l A B C D Cõu 41 (C - 2012): t in ỏp u = U cos2ft (trong ú U khụng i, f thay i c) vo hai u in tr thun Khi f = f1 thỡ cụng sut tiờu th trờn in tr bng P Khi f = f2 vi f2 = 2f1 thỡ cụng sut tiờu th trờn in tr bng P A P B C P D 2P Cõu 42 (C-2011): t in ỏp u = U0cost (U0 v khụng i) vo hai u on mch xoay chiu ni tip gm in tr thun, cun cm thun v t in cú in dung iu chnh c Khi dung khỏng l 100 thỡ cụng sut tiờu th ca on mch t cc i l 100 W Khi dung khỏng l 200 thỡ in ỏp hiu dng gia hai u t in l 100 V Giỏ tr ca in tr thun l A 150 B 120 C 100 D 160 Cõu 43 (H - 2012): t in ỏp u = 150 cos100t (V) vo hai u on mch mc ni tip gm in tr thun 60 , cun dõy (cú in tr thun) v t in Cụng sut tiờu th in ca on mch bng 250 W Ni [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn hai bn t in bng mt dõy dn cú in tr khụng ỏng k Khi ú, in ỏp hiu dng gia hai u in tr bng in ỏp hiu dng gia hai u cun dõy v bng 50 V Dung khỏng ca t in cú giỏ tr bng A 60 B 30 C 15 D 45 Cõu 44: t in ỏp xoay chiu u=120 sin(100t + ) (V) vo hai u on mch gm mt cun dõy 103 F mc ni tip Bit hiu in th hiu dng trờn cun dõy L v trờn t in C bng v bng mt na trờn in tr R Cụng sut tiờu th trờn on mch ú bng A 240W B Khụng tớnh c C 720W D 360W Cõu 45 (C - 2008 ): Mt on mch gm t in cú in dung C, in tr thun R, cun dõy cú in tr thun cm L, mt in tr R v mt t in C= r v h s t cm L mc ni tip Khi t vo hai u on mch hiu in th u U sin t thỡ dũng in mch cú giỏ tr hiu dng l I Bit cm khỏng v dung khỏng mch l khỏc Cụng sut tiờu th on mch ny l A U2 Rr B (r + R ) I2 C I2R D UI 103 Cõu 46: Cho mch in xoay RLC cú R thay i c Cun dõy thun cm cú L (H), C (F) , in ỏp hiu dng hai u mch l u 75 2cos 100t V Cụng sut tiờu th mch P = 45 W in tr R cú th cú nhng giỏ tr no sau: A R= 45 hoc R = 60 B R = 80 hoc R = 160 C R = 45 hoc R = 80 D R = 60 hoc R = 160 Cõu 47: Cho mch in xoay chiu gm cun dõy cú R0 = 50 , L 0,4(H) v t in cú in dung C 104 F v in tr thun R = 30 mc ni tip nhau, ri t vo hai u on mch cú in ỏp xoay chiu u 100 2cos 100t V Cụng sut tiờu th trờn on mch v trờn in tr R ln lt l: A P = 28,8 W; PR = 10,8 W B P = 80 W; PR = 30 W C P = 160 W; PR = 30 W D P = 57,6 W; PR = 31,6 W Cõu 48: on mch in gm cun dõy mc ni tip vi t in lch pha gia in ỏp gia hai u cun dõy, Ud v dũng in l /3 Gi in ỏp gia hai u t in l UC, ta cú UC 3Ud H s cụng sut ca mch in l B 0,5 C D 2 Cõu 49: Mt on mch ni tip gm mt cun dõy v mt t in in ỏp hiu dng hai u on mch, hai u cun dõy, hai u t in u bng Tỡm h s cụng sut cos ca mch ? A C D 2 Cõu 50: Cho on mch AB gm hai on mch AM ni tip MB on mch AM gm in tr R ni tip vi t in cú in dung C, on mch MB cú cun cm cú t cm L v in tr r t vo AB mt in ỏp xoay A 0,5 B chiu u U cos t V Bit R r L ; U AM 2U MB H s cụng sut ca on mch cú giỏ tr l C B C D 2 5 Cõu 51: Mt on mch in xoay chiu gm in tr thun R = 40 , mt cun dõy thun cm cú t cm L= H v t in C mc ni tip t vo hai u on mch ú in ỏp xoay chiu u=200cos(100t+ ) (V) thỡ cụng sut tiờu th ca on mch bng 500 W Biu thc in ỏp gia hai bn t in l A [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn ) (V) B uC = 125 cos(100t - ) (V) C uC = 125 cos(100t - ) (V) D uC = 250cos(100t - ) (V) Cõu 52: Cho on mch ni tip theo th t gm in tr R, t in cú in dung C v cun dõy cú t cm A uC = 250cos(100t - L, in tr r Bit L CR2 Cr t vo on mch in ỏp xoay chiu u U 2cost V thỡ in ỏp hiu dng ca on mch RC gp ln in ỏp hiu dng hai u cun dõy H s cụng sut ca on mch l A 0,866 B 0,657 C 0,785 D 0,5 Cõu 53: Mt on mch in xoay chiu gm mt cun dõy cú in tr thun r = v t cm 0,35 L (H) mc ni tip vi in tr thun R = 30 in ỏp hai u mch l u 70 cos 100t V Cụng sut tiờu th ca on mch l A P 35 W B P = 70 W C P = 35 W D P 30 W Cõu 54: on mch AB gm in tr R = 40 , mt cun dõy thun cm cú t cm L (H) v t in C mc ni tip t vo hai u on mch ú mt in ỏp xoay chiu u 160cos 100t thỡ cụng sut tiờu th trờn on mch ú bng 320 W Biu thc in ỏp trờn hai u t in l A uC 80 2cos 100 t B khụng iu kin xỏc nh C uC 120cos 100t D uC 240cos 100 t 3 Cõu 55: on mch xoay chiu gm in tr R0 mc ni tip vi mt hp kớn X Khi t vo hai u mch mt in ỏp xoay chiu cú giỏ tr hiu dung U thỡ in ỏp hiu dng hai u R0 v hp X ln lt l 0,8U v 0,5U H s cụng sut ca mch chớnh bng A 0,87 B 0,67 C 0,50 D 0,71 L Cõu 56: Cho on mch RLC vi R t vo hai u on mch trờn in ỏp xoay chiu vi in ỏp hiu C dng khụng i, thay i c) Khi v 91 thỡ mch cú cựng h s cụng sut, giỏ tr h s cụng sut ú l 2 A B C D 73 13 21 67 Cõu 57: on mch AB gm hai hp en X, Y mc ni tip, mi hp ch cha mt linh kin thuc loi in tr thun, cun dõy hoc t in t vo u on mch AB mt in ỏp u=100 cos2ft (V) vi f thay i c Khi iu chnh tn s n giỏ tr f0 thỡ in ỏp hiu dng gia hai u hp X v Y ln lt l UX = 200V v UY = 100 V Sau ú bt u tng f thỡ cụng sut ca mch tng H s cụng sut ca on mch AB lỳc cú tn s cú giỏ tr f0 l A 13 B 0,5 C B C D Cõu 58: Cho mch in xoay chiu RLC mc ni tip, cun dõy thun cm Bit L = CR2 t vo hai u on mch in ỏp xoay chiu n nh, mch cú cựng h s cụng sut vi hai giỏ tr ca tn s gúc 50 (rad / s) v 200 (rad / s) H s cụng sut ca on mch bng A [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] D 12 Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn Cõu 59: Cho mch in xoay chiu RLC mc ni tip, cun dõy thun cm Bit L 4CR2 t vo hai u on mch in ỏp xoay chiu n nh, mch cú cựng h s cụng sut vi hai giỏ tr ca tn s gúc 50 rad / s v 200 rad / s H s cụng sut ca on mch bng A B C 2 D 13 10 13 10 Cõu 60: t in ỏp xoay chiu cú tn s f thay i c vo hai u on mch gm t in cú in dung C v in tr thun R mc ni tip Khi tn s l f1 thỡ h s cụng sut ca on mch l cos1 Khi tn s l f2 = 3f1 thỡ h s cụng sut ca on mch l cos2 = cos1 Giỏ tr ca cỏc h s cụng sut l A cos1 = 2 ; cos2 = 5 B cos1 = ; cos2 = C cos1 = ; cos2 = 5 D cos1 = ; cos2 = 14 Cõu 61: t in ỏp u U cos2ft (trong ú U khụng i, f thay i c) vo hai u on mch gm R v C mc ni tip Khi tn s l f1 hoc f2 3f1 thỡ h s cụng sut tng ng ca on mch l cos1 v cos2 vi cos cos Khi tn s l f3 f1 h s cụng sut ca on mch cos3 bng 7 5 B C D 5 Cõu 62: Mc vo on mch RLC khụng phõn nhỏnh gm mt ngun in xoay chiu cú tn s thay i c tn s f1 60Hz , h s cụng sut t cc i cos tn s f2 120Hz , h s cụng sut nhn giỏ A tr cos 0,707 tn s f3 90Hz , h s cụng sut ca mch bng: A 0,872 B 0,486 C 0,625 D 0,781 Cõu 63: t vo on mch RLC ni tip mt in ỏp xoay chiu u=U0cos2ft (V), ú tn s f cú th thay i c Khi tn s l f1 v 4f1 thỡ cụng sut mch nh v bng 80% cụng sut cc i m mch cú th t c Khi f = 5f1 thỡ h s cụng sut ca mch in l A 0,75 B 0,82 C 0,53 D 0,46 Cõu 64: t in ỏp xoay chiu u U0 cos2ft V (trong ú U0 khụng i, f thay i c) vo hai u on mch mc ni tip gm in tr R v t in C mc ni tip Khi tn s bng 20Hz thỡ cụng sut tiờu th ca on mch l 10 W; tn s bng 40Hz thỡ cụng sut tiờu th ca on mch l 20 W Khi tn s bng 60Hz thỡ cụng sut tiờu th ca on mch l A 30 W B 40 W C 24,5 W D 28,9 W Cõu 65: Cho on mch xoay chiu RLC mc ni tip Bit R 60 , cun cm thun, t in cú in dung C thay i c in ỏp xoay chiu gia hai u on mch luụn n nh Cho C thay i, 103 103 F thỡ cụng sut tiờu th ca mch u nh Bit cng dũng F hoc C C 14 in qua mch C C1 l i1 3 cos( 100t ) A Khi C C thỡ h s cụng sut ca on mch cú giỏ tr ln nht Lp biu thc cng dũng in qua mch C C C C1 H Mc ampe k cú in tr khụng ỏng k vo hai u cun dõy thỡ thy cụng sut ca mch khụng thay i in dung ca t l Cõu 66: Mch R, L, C khụng phõn nhỏnh in ỏp hai u on mch l u=Uosin(100t) (V), vi L A F 104 B 104 F C 102 F [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] D 2.104 F Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn Cõu 67: Điện áp hai đầu on mch RLC ni tip l u 200cos(100t) (V) Cho C thay đổi, có hai giá trị 103 104 F F cng dũng in hiu dng mch 5A Cụng sut ca on mch hai trng hp l A 500 W B 1000 W C 2000 W D 800 W C: Cõu 68: Cho on mch RLC, t vo on mch in ỏp xoay chiu u U cos100t (V) Khi giỏ tr hiu dng U = 100 V, thỡ cng dũng in mch tr pha hn in ỏp l v cụng sut ta nhit ca on mch l 50 W Khi in ỏp hiu dng U 100 V , cng dũng in hiu dng khụng i thỡ cn ghộp ni tip vi on mch trờn in tr R cú giỏ tr: A 73,2 B 50 C 100 D 200 Cõu 69: t mt hiu in th xoay chiu u 120 cos100t (V) vo hai u mt mch in xoay chiu ni ng thi I 1,5 A Sau ú, ni tip thờm vo mch trờn in tr R v t C thỡ cụng sut ta nhit trờn R l 90 W Giỏ tr ca R v C phi l tip gm R1 v cun dõy thun cm L thỡ u lch pha so vi i l A 40 v 104 (F) B 50 v 104 (F) 2,5.104 2,5.104 D 50 v (F) (F) Cõu 70: Mch in xoay chiu gm in tr thun R = 20 () mc ni tip vi cun dõy t vo hai u C 40 v mch mt in ỏp xoay chiu cú in ỏp hiu dng U v tn s f in ỏp hiu dng hai u cun dõy l Ud = 90 V Dũng in mch lch pha so vi u v lch pha so vi ud Cụng sut tiờu th in ca on mch bng A 900 W B 405 W C 607,5 W D 346,5W Cõu 71: Mch in RLC nh hỡnh v t di in ỏp xoay chiu n nh Khi R C K ngt, in ỏp hai u mch tr pha 450 so vi cng dũng in qua mch T s cụng sut ta nhit trờn mch trc v sau úng khúa K bng Cm A K khỏng ZL cú giỏ tr bng my ln in tr thun R? L B A B 0,5 C D Cõu 72: t in ỏp xoay chiu cú biu thc u U0 cos(100t) vo hai u on mch RLC ni tip Ti thi im cng dũng in mch cú ln cc i thỡ in ỏp hai u on mch cú ln 3U Khong thi gian ngn nht gia hai thi im m cụng sut tc thi bng khụng l: 1 1 A B C D s s s s 100 150 300 600 Cõu 73: t in ỏp xoay chiu u = U0.cos(100t + /6) (V) vo hai u on mch xoay chiu RLC mc ni tip Bit ti thi im cng dũng in qua mch cú ln cc i thỡ in ỏp hai u mch ang cú ln bng U0/2 Khong thi gian ngn nht gia hai thi im m cụng sut tc thi bng l A 1/600 s B 1/150 s C 1/300 s D 1/100 s Cõu 74: Cho on mch khụng phõn nhỏnh gm hai on mch AM v MB, ú AM l cun dõy khụng thun cm t in ỏp xoay chiu u 100 cos100t V vo hai u AM thỡ dũng in cú cng hiu dng I1 = A v lch pha vi in ỏp hai u on mch gúc 300 Khi t in ỏp vo hai u on mch AB thỡ dũng in cú cng hiu dng I2 = A v cỏc in ỏp tc thi hai u on mch AM v MB lch pha Cụng sut tiờu th ca on mch AB bng: [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn A 75 W B 50 W C 50 W D 25 W Cõu 75: t mt in ỏp xoay chiu vo hai u on mch AB ni gm RLC Gia AN cha R v cun dõy thun cm L, gia MB cha R v C Bit UAN = 100V, UMB = 75V, I = Ni dung no sau õy l sai ? A v uAN vuụng pha vi uMB A Cụng sut tiờu th ca mch l 30 W B in ỏp uAB sm pha hn i C Giỏ tr ca ZL l 40 D Cụng sut tiờu th ca mch l 60 W DNG 2: CễNG SUT KHI Cể CNG HNG IN Cõu 1: Khi xy hin tng cng hng mch in xoay chiu gm R, L, C mc ni tip thỡ biu thc no sau õy sai? A cos = B ZL = ZC C UL = UR D U = UR Cõu (H 2008): on mch in xoay chiu khụng phõn nhỏnh gm cun dõy cú t cm L, in tr thun R v t in cú in dung C Khi dũng in cú tn s gúc chy qua on mch thỡ h s cụng sut LC ca on mch ny A ph thuc in tr thun ca on mch B bng C ph thuc tng tr ca on mch D bng Cõu 3(C - 2011 ): Khi núi v h s cụng sut cos ca on mch xoay chiu, phỏt biu no sau õy sai? A Vi on mch ch cú t in hoc ch cú cun cm thun thỡ cos=0 B Vi on mch cú in tr thun thỡ cos C Vi on mch cú R, L, C mc ni tip ang xy cng hng thỡ cos=0 D Vi on mch gm t in v in tr thun mc ni tip thỡ cos Cõu (H - 2011): t in ỏp u U cos2ft (U khụng i, tn s f thay i c) vo hai u on mch mc ni tip gm in tr thun R, cun cm thun cú t cm L v t in cú in dung C Khi tn s l f1 thỡ cm khỏng v dung khỏng ca on mch cú giỏ tr ln lt l v Khi tn s l f2 thỡ h s cụng sut ca on mch bng H thc liờn h gia f1 v f2 l A f2 f1 B f2 f1 C f2 f1 4 D f2 f1 3 Cõu 5: Trong on mch xoay chiu gm in tr R, t in cú in dung C biờn i c v cun dõy ch cú t cm L mc ni tip vi in ỏp tc thi mch l u = U 0cos100t (V) Ban u lch pha gia u v i l 600 thỡ cụng sut tiờu th ca mch l 50 W Thay i t C uAB cựng pha vi i thỡ mch tiờu th cụng sut: A 200 W B 50 W C 100 W D 120 W Cõu 6: t in ỏp u 100 cos100t (V) vo hai u on mch RLC khụng phõn nhỏnh vi C, R cú H Khi ú in ỏp hiu dng hai u mi phn t R, L, C cú ln nh Cụng sut tiờu th ca on mch l A 50 W B 100 W C 200 W D 350 W ln khụng i v L Cõu 7: Ln lt t in ỏp xoay chiu u = 100 cos(2ft) V, vi f khụng i, vo hai u mi phn t: in tr thun cm v t in thỡ dũng in qua mi phn t trờn u cú cựng mt giỏ tr hiu dng l A Khi t in ỏp ny vo hai u on mch gm cỏc phn t trờn mc ni tip thỡ cụng sut tiờu th ca on mch l: A 150 W B 100 W C 100 W D 200 W Cõu 8: t mt in ỏp xoay chiu u = Uocos(100t) vo hai u on mch gm in tr thun R, cun cm H v t in C mc ni tip Trong mch cú cng hng in v cụng sut tiờu th ca on mch l 400W Nu cun cm b ni tt thỡ cụng sut tiờu th ca on mch l 100W Giỏ tr R bng thun L [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang 10 Thy Ngc H Vin Vt Lớ - hocmai.vn IN XOAY CHIU A 100 B 100 C 200 D 200 Cõu 9: Cú ba dng c gm in tr thun R 30, cun cm thun L v t in C t in ỏp xoay chiu u U0 cos(t ) (V) ln lt vo hai u on mch ni tip gm RL v RC ú cng dũng in 10 mch i1 6cos(t ) (A) v i 6cos(t ) (A) t in ỏp trờn vo hai u on mch RLC 21 mc ni tip thỡ cụng sut mch in lỳc ú bng A 960 W B 720 W C 480 W D 240 W Cõu 10: Cho on mch xoay chiu RLC mc ni tip Khi t vo hai u mch mt hiu in th xoay chiu n nh cú tn s f tho 42f2L.C = Nu thay i giỏ tr in tr R thỡ A lch pha gia u v i thay i B cụng sut tiờu th in trung bỡnh trờn mch khụng i C h s cụng sut ca mch thay i D in ỏp hiu dng gia hai u bin tr khụng i DNG 3: XC NH H S CễNG SUT QUA LCH PHA CC PHNG TRèNH IN P, DếNG IN CHO TRC Cõu 1: on mch AB gm hai on mch AM v MB mc ni tip on AM gm in tr thun R = 100 mc ni tip vi cun cm thun L H on MB l t in cú in dung C Biu thc in ỏp trờn on mch AM v MB ln lt l uAM 100 2cos 100t V v uMB 200cos 100t V H s cụng sut ca on mch AB l: B C 0,5 D 0,75 2 Cõu 2: on mch AB ni tip gm ch cỏc phn t nh in tr thun , cun cm v t in on mch AB gm hai on mch AM v MB mc ni tip on AM gm in tr thun R = 50 mc ni tip vi t in A cú in dung khỏng 50 Biu thc in ỏp trờn on mch AM v MB ln lt l: uAM 80cos 100t V v uMB 100cos 100t V H s cụng sut ca on mch AB l: A 0,99 B 0,84 C 0,86 D 0,95 Cõu (H - 2011): on mch AB gm hai on mch AM v MB mc ni tip on mch AM gm in 103 F , on mch MB gm in tr thun R2 mc ni tip vi cun cm thun t vo A, B in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i thỡ in ỏp tc thi hai u on mch AM v MB ln lt l : uAM 50 cos(100t )(V) v 12 uMB 150cos100t (V) H s cụng sut ca on mch AB l tr thun R1 = 40 mc ni tip vi t in cú din dng C A 0,86 B 0,84 C 0,95 D 0,71 Cõu 4: on mch AB gm hai on mch AM v MB mc ni tip on AM gm in tr thun R1 = 50 mc ni tip vi t in cú in dung C 2.104 F , on mch MB gm in tr thun R2 mc vi cun thun cm t vo A, B in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i thỡ in ỏp tc thi hai u on mch AM v MB ln lt l uAM 50 2cos 100t V v uMB 100 cos 100t V H s 3 cụng sut ca on mch AB l A 0,84 B 0,96 C 0,81 D 0,91 [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang 11 Thy Ngc H Vin Vt Lớ - hocmai.vn IN XOAY CHIU Cõu 5: on mch AB gm hai on mch AM v MB mc ni tip on AM gm in tr thun R1 = 70 2.104 F , on mch MB gm in tr thun R2 mc vi cun thun cm t vo A, B in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i thỡ in ỏp tc thi hai u mc ni tip vi t in cú in dung C on mch AM v MB ln lt l uAM 80cos 100t V v uMB 90cos 100t V H s cụng sut ca on mch AB l A 0,97 B 0,96 C 0,86 D 0,99 Cõu 6: Mt on mch xoay chiu gm phn t mc ni tip l in tr thun R, cun dõy cú t cm L v in tr thun r, t in cú in dung C t vo hai u on mch mt in ỏp xoay chiu, ú in ỏp tc thi hai u cun dõy v hai u t in ln lt cú biu thc ud 80 cos t / V , uC 40 2cos t / V , in ỏp hiu dng hai u in tr l UR = 60 V H s cụng sut ca on mch trờn l A 0,862 B 0,908 C 0,753 D 0,664 Cõu 7: Mt on mch xoay chiu gm phn t mc ni tip l in tr thun R, cun dõy cú t cm L v in tr thun r, t in cú in dung C t vo hai u on mch mt in ỏp xoay chiu, ú in ỏp tc thi hai u cun dõy v hai u t in ln lt cú biu thc ud 100 2cos t V , uc 100 6cos t V , in ỏp hiu dng hai u in tr l UR = 100 V H s cụng sut ca on mch trờn l 0,862 B C D 0,82 2 Cõu 8: on mch xoay chiu AB cú in tr R1 mc ni tip vi on mch R2C, in ỏp hiu dng hai u R1 v hai u on mch R2C cú cựng giỏ tr, nhng lch pha /3 Nu mc ni tip thờm cun dõy thun cm thỡ cos = v cụng sut tiờu th l 200 W Nu khụng cú cun dõy thỡ cụng sut tiờu th ca mch l bao nhiờu? A 160 W B 173,2 W C 150 W D 141,42 W A Cõu 9: Cun dõy cú in tr thun R v t cm L mc vo in ỏp xoay chiu u 250 2cos 100t V thỡ cng dũng in hiu dng qua cun dõy l 5A v dũng in ny lch pha 600 so vi in ỏp u Mc ni tip cun dõy vi on mch X to thnh on mch AB ri li t vo hai u on mch AB in ỏp u núi trờn thỡ cng dũng in hiu dng qua mch l 3A v in ỏp hai u cun dõy vuụng pha vi in ỏp hai u X Cụng sut tiờu th trờn on mch X l A 200 W B 300 W C 200 W D 300 W Cõu 10: Cho on mch in AB gm hai on mch AM v MB mc ni tip on AM gm m in tr thun R1 mc ni tip vi t in cú in dung C, on mch MB gm mt in tr thun R2 mc ni tip vi mt cun cm thun cú t cm L t in ỏp xoay chiu cú tn s f v cú giỏ tr hiu dng LC luụn khụng i vo on mch AB Khi ú on mch AB tiờu th cụng sut P1 Nu ni tt hai u cun cm thỡ in ỏp hai u mch AM v MB cú cựng giỏ tr hiu dng nhng lch pha /3, cụng sut tiờu th ca on mch AB trng hp ny bng 180 W Giỏ tr ca P1 l A 320 W B 360 W C 240 W D 200 W Cõu 11: t in ỏp xoay chiu u = U cost (V) vo hai u on mch RLC mc ni tip, cun dõy thun cm Khi ni tt t C thỡ in ỏp hiu dng gia hai u in tr R tng ln v dũng in hai trng hp vuụng pha H s cụng sut ca on mch lỳc sau bng [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang 12 IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn A 2 B C D Cõu 12: t in ỏp xoay chiu u = U cost (V) vo hai u on mch RLC mc ni tip, cun dõy thun cm Khi ni tt t C thỡ in ỏp hiu dng gia hai u in tr R tng ln v dũng in hai trng hp vuụng pha H s cụng sut ca on mch lỳc trc l 2 1 A B C D 5 Cõu 13: t in ỏp xoay chiu vo hai u on mch RLC ni tip, cun dõy thun cm Khi ni tt t C thỡ in ỏp hiu dng gia hai u in tr R tng ln v dũng in hai trung hp vuụng pha vi H s cụng sut on mch lỳc sau bng: A B C D 5 10 10 Cõu 14: t in ỏp xoay chiu n nh vo hai u on mch gm cun dõy khụng thun cm ni tip vi t in, vụn k nhit mc vo hai u cun dõy Nu ni tt t in thỡ s ch vụn k tng ln v cng dũng in tc thi hai trng hp vuụng pha vi H s cụng sut ca mch in lỳc u l A 3/ 10 B 1/ 10 C 1/ D 1/3 Cõu 15: t in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i vo hai u on mch gm bin tr R mc ni tip vi t in cú in dung C Gi in ỏp hiu dng gia hai u t in, gia hai u bin tr v h s cụng sut ca on mch bin tr cú giỏ tr R1 ln lt l UC1, UR1 v cos1; bin tr cú giỏ tr R2 thỡ cỏc giỏ tr tng ng núi trờn l UC2, UR2 v cos2 Bit UC1 = 2UC2, UR2 = 3UR1 Giỏ tr ca cos1 v cos2 l A cos1 C cos1 35 , cos2 , cos2 35 B cos1 32 32 , cos2 35 35 D cos1 3 , cos2 35 35 35 35 Cõu 16: t in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i vo hai u on mch gm bin tr R mc ni tip vi cun thun cm Gi in ỏp hiu dng gia hai u cun cm, gia hai u bin tr v h s cụng sut ca on mch bin tr cú giỏ tr R1 ln lt l UL1; UR1 v cos1 , bin tr cú giỏ tr R2 thỡ cỏc giỏ tr tng ng núi trờn l UL2; UR2 v cos2 Bit 3UR2 = 4UR1 T s cos1 / cos2 bng A 0,75 B 0,31 C 0,49 D 0,64 Cõu 17: t in ỏp xoay chiu cú giỏ tr hiu dng v tn s khụng i vo hai u on mch gm bin tr R mc ni tip vi t in cú in dung C Gi in ỏp hiu dng gia hai u t in, gia hai u bin tr v h s cụng sut ca on mch bin tr cú giỏ tr R1 ln lt l UC1, UR1 v cos1; bin tr cú giỏ tr R2 thỡ cỏc giỏ tr tng ng núi trờn l UC2, UR2 v cos2 Bit UC1 = 3UC2, UR2 = UR1 Giỏ tr ca cos1 v cos2 l A cos1 , cos2 13 13 B cos1 C cos1 3 , cos2 13 13 D cos1 13 13 , cos2 , cos2 13 13 DNG 4: XC NH LCH PHA u V i QUA GI TR TC THI TI THI IM, T ể XC NH CễNG SUT, H S CễNG SUT Cõu 1: Mt mch in xoay chiu gm AM ni tip MB Bit AM gm in tr thun R1, t in C1, cun dõy thun cm L1 mc ni tip on MB cú hp X, bit hp X cng cú cỏc phn t l in tr thun, cun cm, t in mc ni tip t in ỏp xoay chiu vo hai u mch AB cú tn s 50 Hz v giỏ tr hiu dng l 200 V thỡ thy dũng in mch cú giỏ tr hiu dng [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] A Bit R1 = 50 v nu thi Trang 13 IN XOAY CHIU Thy Ngc H Vin Vt Lớ - hocmai.vn im t (s), uAB = 200 V v ang tng thỡ thi im t s dũng in i = A v ang gim Cụng sut 300 ca on mch MB l A 300 W B 120 W C 200 W D 150 W Cõu 2: Mt mch in xoay chiu gm AM ni tip MB Bit AM gm in tr thun R1, t in C1, cun dõy thun cm L1 mc ni tip on MB cú hp X, bit hp X cng cú cỏc phn t l in tr thun, cun cm, t in mc ni tip t in ỏp xoay chiu vo hai u mch AB cú tn s 50 Hz v giỏ tr hiu dng l 200 V thỡ thy dũng in mch cú giỏ tr hiu dng A Bit R1 = 20 v nu thi im t (s), uAB = 200 V thỡ thi im t s dũng in i = v ang gim Cụng sut ca on mch MB 600 l A 266,4 W B 120 W C 320 W D 400 W Cõu 3: t in ỏp u = 200cos(100t) V vo hai u on mch AB gm in tr thun 60 mc ni tip vi on mch X Cng dũng in hiu dng qua mch l A Bit ti thi im t in ỏp tc thi gia hai u mch l 200 V, thi im t s cng dũng in qua mch bng v ang gim Tớnh cụng 400 sut tiờu th ca on mch X? A 60 W B 120 W C 100 W D 40 W Cõu 4: t in ỏp u = 100 cos(100t) V vo hai u on mch AB gm in tr thun 30 mc ni tip vi on mch X Cng dũng in hiu dng qua mch l A Bit ti thi im t in ỏp tc thi gia hai u mch l 200 V, thi im t s cng dũng in qua mch bng v ang gim Cụng 300 sut tiờu th ca on mch X v ton mch AB l ? A 60 W v 150 W B 60 v 120 W C 80 W v 150 W D 40 W v 80 W Cõu (H 2012): t in ỏp u = 400cos(100t) V vo hai u on mch AB gm in tr thun 50 mc ni tip vi on mch X Cng dũng in hiu dng qua mch l A Bit ti thi im t in ỏp tc thi gia hai u mch l 400 V, thi im t s cng dũng in qua mch bng v ang gim 400 Tớnh cụng sut tiờu th ca on mch X? A 100 W B 120 W C 200 W D 400 W Dng 5: Cụng Sut Mch Mt Chiu V Xoay Chiu Cõu 1: on mch gm cun dõy thun cm v in tr R ni tip Nu t vo hai u on mch in ỏp chiu 24 V thỡ cng dũng in l 0,48 A Nu t in ỏp xoay chiu thỡ cng dũng in hiu dng l A Cụng sut tiờu th ca on mch lỳc mc vo in ỏp xoay chiu l A 100 W B 200 W C 50 W D 11,52 W 0,4 Cõu 2: t vo hai u mt cun dõy cú t cm L (H) mt in ỏp mt chiu U1 = 12 V thỡ cng dũng in qua cun dõy l I1 = 0,4 A Nu t vo hai u cun dõy ny mt in ỏp xoay chiu cú giỏ tr hiu dng U2 = 12 V, tn s f = 50 Hz thỡ cụng sut tiờu th cun dõy bng A 1,2 W B 1,6 W C 4,8 W D 1,728 W Dng 6: Cụng Sut Mch Cha ng C in Cõu (H-2014): Mt ng c in tiờu th cụng sut in 110 W, sinh cụng sut c hc bng 88 W T s ca cụng sut c hc vi cụng sut hao phớ ng c bng A B C D [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang 14 Thy Ngc H Vin Vt Lớ - hocmai.vn IN XOAY CHIU Cõu (H - 2012): Mt ng c in xoay chiu hot ng bỡnh thng vi in ỏp hiu dng 220V, cng dũng in hiu dng 0,5 A v h s cụng sut ca ng c l 0,8 Bit rng cụng sut hao phớ ca ng c l 11 W Hiu sut ca ng c (t s gia cụng sut hu ớch v cụng sut tiờu th ton phn) l A 80% B 90% C 92,5% D 87,5 % Cõu 3: Mt ng c in xoay chiu hot ng bỡnh thng vi in ỏp hiu dng 220V v dũng in hiu dng bng 0,5A Nu cụng sut ta nhit trờn dõy cun l 8,8W ( b qua cỏc hao phớ khỏc), h s cụng sut ca ng c bng 0,8 thỡ hiu sut ca ng c l A 95% B 98% C 90% D 86% Cõu 4: Khi mc mt ng c in xoay chiu cú h s cụng sut cos 0,9 vo mch in xoay chiu cú in ỏp hiu dng U 200V thỡ sinh mt cụng sut c hc P 324W Hiu sut ca ng c H 90% in tr thun ca ng c l: A 10 B C 100 D Cõu 5: Trờn mt ng c in xoay chiu mt pha cú ghi in ỏp hiu dng nh mc U 220V, h s cụng sut ca ng c l cos 0,95 Khi ng c hot ng bỡnh thng, dũng in chy qua ng c l 5A v hiu sut ca ng c l 89% in tr thun ca ng c bng A 4,6 B 8,25 C 44 D 41,8 Cõu 6: Mt ng c in xoay chiu hot ng bỡnh thng vi in ỏp hiu dng 200 V thỡ sinh cụng sut c l 320 W Bit in tr thun ca dõy qun ng c l 20 v h s cụng sut ca ng c l 0,89 Cng d dũng in hiu dng chy ng c l A (A) B 2,5 (A) C 4,4 (A) D 1,8 (A) [Facebook: https://www.facebook.com/ha.dongoc][ST: 0168.5315.249] Trang 15