Thay Dang Viet Hung - 101 Cau Trac Nghiem Dien Xoay Chieu Hay Va Kho-V2

Kha hc Luyn thi H mnVt l Gio vin: ng Vit Hng 101 cu trc nghim in xoay chiu hay v kh

Hocmai.vn Ngi trng chung ca hc tr Vit Tng i t vn: 1900 58-58-12 - Trang | 1 -

Cu 1: Cho on mch RLC ni tip c R = 50 ; L = 159 mH, C = 31,8 F . in p hai u on mch c biu

thc u = 120cos100t(V). Nhit lng ta ra trn in tr R trong 1 pht l:

A. 1000 J. B. 4320 J. C. 432 J. D. 200 J.

Cu 2: Mt n ng hunh quang c t di hiu in th c gi tr cc i 127 V v tn s 50 Hz. Bit n ch

sng khi hiu in th tc thi t vo n u 90V . Tinh thi gian trung bnh n sng trong mi pht?

A. 30 s B. 40 s C. 20 s D. 1 s

Cu 3: Cho mch in RCL mc ni tip theo th t R, C, L, trong cun dy thun cm c t cm L thay i

c; R = 100 . t vo hai u on mch hiu in th xoay chiu tn s f = 50 Hz. Thay i L ngi ta thy

khi L = L1 v khi 1

2

LL L

2 th cng sut tiu th trn on mch nh nhau nhng cng dng in tc thi

vung pha nhau. Gi tr ca L1 l

A. 11

L (H).

B. 12

L (H).

C. 14

L (H).

D. 11

L (H).2

Cu 4: Mch RLC c 2L

RC

v tn s thay i c. Khi f = f1 hoc f = f2 th mch c cng h s cng sut. Bit

f2 = 4f1. Tnh h s cng sut ca mch khi .

A. 13

.4

B. 2

.13

C. 2

.13

D. 6

.3

Cu 5: Cho on mch AB gm hai on mch AM ni tip MB. on mch AM gm in tr R ni tip vi t

in c in dung C, on mch MB c cun cm c t cm L v in tr r. t vo AB mt in p xoay chiu

u U 2 cos t V. Bit AM MBL

R r ; U 2U .C

H s cng sut ca on mch c gi tr l

A. 3

.2

B. 2

.2

C. 3

.5

D. 4

.5

Cu 6: Mt on mch AB gm hai on mch, AM v MB mc ni tip. on mch MB c in tr R mc ni

tip vi t C, t in c dung khng gp 3 ln in tr R. Gi in p hiu dng gia hai u on mch MB khi

cun cm c gi tr L1 v L2 tng ng l U1 v U2. Bit 2 1 1 297

L 5L ;U U .5

H s cng sut ca mch AB khi

L = L1 l

A. 5

.194

B. 5

.97

C. 2

.25

D. 10

.97

Cu 7: Ngi ta dng mt vn kt (c in tr rt ln) v mt in tr bit R = 100 xc nh in dung C

ca mt t, in tr r cng h s t cm L ca mt cun dy. Ln u mc t ni tip vi cun dy vo mt hiu

in th xoay chiu f = 50 Hz, v o c cc hiu in th U = 200 V hai u on mch, Ud = 80 5 V hai u

101 CU TRC NGHIM IN XOAY CHIU HAY V KH

Gio vin: NG VIT HNG

y l ti liu 101 cu trc nghim in xoay chiu hay v kh thuc kha hc Luyn thi i hc

mn Vt l thy ng Vit Hng. c th nm vng ton b kin thc n thi i hc mn Vt l,

Bn nn tham gia kha hc Luyn thi i hc mn Vt l thy ng Vit Hng ti Hocmai.vn



cun dy, UC = 200 V hai u t. Ln hai mc thm in tr R ni tip vi t v cun dy vo mch in ri o

hiu in th hai u t c C200 5

U ' 3

a) Hy tnh r, L, C

A. 200 ; 0,318 H; 12,7 F B. 200 ; 0,626 H; 12,7 F

C. 100 ; 0,626 H; 12,7 F D. 100 ; 0,318 H; 12,7 F

b) Tnh cng sut tiu th trong mi trng hp trn

A. 28 W; 53 W B. 128 W; 53 W C. 280 W; 530 W D. 12 W; 5 W

Cu 8: Cho on mch RLC mc ni tip. R = 50 , 42.10

C F3

, cun dy thun cm. t vo hai u on

mch mt hiu in th u 100 2 cos 100t V , Mc kha K song song vi cun dy. Khi K ng hay m th

cng dng in hiu dng trong mch nh nhau. Tnh L v I ?

A. 0,55 H; 1 A B. 1 H; 0,5 A C. 0,5 H ; 2 A D. 2 H; 0,5 A

Cu 9: Cho ba linh kin gm in tr thun R = 60 , cun cm thun L v t in C. Ln lt t in p xoay

chiu c gi tr hiu dng U vo hai u on mch ni tip RL hoc RC th biu thc cng dng in trong

mch ln lt l 1

i 2cos 100t A12

v 25

i 2cos 100t A12

. Nu t in p trn vo hai u on mch

RLC ni tip th dng in trong mch c biu thc:

A.

i 2cos 100t A3

B.

i 2 2 cos 100t A6

C.

i 2 2 cos 100t A4

D.

i 2cos 100t A6

Cu 10: Cho mch RLC ni tip. in p xoay chiu gia hai u on mch l u 120 2 cos(100t)V . t cm

L ca cun dy thun cm thay i c. iu chnh L th thy khi 0,4

L H

th in p hiu dng gia bn t cc

i bng 80 3 V. in tr R ca mch c gi tr

A. 10 . B. 10 3 . C. 20 3 . D. 15 .

Cu 11: Cng dng in tc thi qua mch in xoay chiu RLC ni tip l i = I0cos(t) khi t vo hai u

on mch mt in p xoay chiu u = U0cos(t + ). Cng sut tc thi ca on mch c xc nh theo

cng thc:

A. 0 0p U I cos cos t B. 0 0p 0,5U I cos

C. 0 0p 0,5U I cos cos 2t D. 0 0p U I cos

Cu 12: Cho on mch RLC ni tip, trong R thay i c. Hiu in th hiu dng hai u on mch l U.

Khi R thay i c hai gi tr R1 v R2 ca R mch c cng cng sut v lch pha ca u v i tng ng l 1 v

2

a) Tm h thc lin h gia R1 v R2

A. 2

2

1 2 1 2 L C

UR R ;R .R Z Z

2P B.

22

1 2 1 2 L C

2UR R ;R .R Z Z

P

C. 2

2

1 2 1 2 L C

UR R ;R .R Z Z

P D.

22

1 2 1 2 L C

UR R ;R .R Z Z

P

b) Tm h thc lin h gia 1 v 2

A. 1 2 B. 2

1 2

4 C. 1 2

3 D. 1 2

2



Cu 13: Cho ABu 220 2cos(100t)V t vo on mch gm 3 phn t R, L = 2/ (H), 410

C F

. Khi R = R1

th cng sut mch t cc i l P1. Khi R = R2 hoc R = R3 th PAB = P2 = P3 < P1. Tm quan h R1, R2, R3

A. 1 2 3R R R B. 2 3

1

2 3

R RR

R R C.

21 2 3R R R D.

21 2 3R 2R R

Cu 14: Cho mch in xoay chiu RLC mc ni tip, in tr R thay i c. Cun dy khng thun cm c in

tr r. Khi R = R1 hoc R = R2 th mch tiu th cng sut bng nhau.

a) Tm R cng sut trong mch t gi tr cc i v gi tr cc i ?

A. 2

1 2 ABmax

UR R r R r r;P

R r B.

2

1 2 ABmax

UR R r R r r;P

2 R r

C. 2

1 2 ABmax

UR 2 R R r r;P

2 R r D.

2

1 2 ABmax

UR R r R r r;P

2 R r

b) Tm R cng sut tiu th trn bin tr R t cc i v gi tr cc i ?

A. 2

L C R max

UR Z Z ;P

R r B.

2

L C R max

UR Z Z r;P

2 R r

C. 2

22L C R max

UR r Z Z ;P

2 R r. D.

2

R max

UR 0;P

2r

Cu 15: Cho on mch RLC ni tip, cun dy thun cm c t cm L thay i c. Khi L = L1 hoc L = L2

th cng sut (hoc dng in hoc lch pha) ca mch c gi tr nh nhau. Hi vi gi tr no ca L th cng

sut ca mch c gi tr cc i:

A. 1 2L L L B. 1 2L LL

2

C. 1 2

1 1 1

L L L D.

1 2

1 1 1 1

L 2 L L

Cu 16: Cho on mch RLC ni tip, t c in dung thay i c. Khi C = C1 hoc C = C2 th cng sut ca

on mch c gi tr bng nhau. cng sut trong mch t gi tr cc i th in dung C bng:

A. 1 2C C C B. 1 2C CC

2

C. 1 2

1 1 1

C C C D.

1 2

1 1 1 1

C 2 C C

Cu 17: Cho on mch RLC mc ni tip vo mch in c tn s f thay i. Ngi ta thy rng c hai gi tr ca

tn s f1 v f2 mch cho cng mt gi tr cng sut P1 = P2. Thay i f n tn s f0 th thy cng sut ca mch t

cc i. Tm f0

A. 0 1 2f f f B. 2 2

0 1 2f f f C. 2 2 20 1 2

1 1 1

f f f D. 0 1 2f f .f

Cu 18: Cho A, M, B l 3 im lin tip trn mt on mch xoay chiu khng phn nhnh, bit biu thc hiu

in th trn cc on AM, MB ln lt l uAM = 40cos(t + /6) V; uMB = 50cos(t + /2) V. Hiu in th cc i

gia hai im A, B c gi tr

A. 60,23 V. B. 78,1 V. C. 72,5 V. D. 90 V.

Cu 19: Cho mch in xoay chiu gm in tr thun R, cun dy thun cm L v t in C = 1/ (mF) mc ni

tip. Biu thc ca hiu in th gia hai bn t in l 3

u 50 2 cos 100t V4

. Cng dng in trong

mch khi t = 0,01 s l

A. 5 2 A. B. 5 2 A C. 5 A D. 5 A



Cu 20: Cho mch in xoay chiu AB gm hai on AN v NB mc ni tip, on AN ch c cun cm thun L =

5

3H, on NB gm R = 100 3 v t in c in dung C thay i c. t vo hai u on mch AB mt

in p xoay chiu n nh u U 2cos(120t)V . in p hiu dng trn on mch NB t cc i th in

dung ca t in bng

A. 10-4/(3,6) F. B. 10-4/(1,8) F. C. 10-4/(36) F D. 10-4/(7,2) F.

Cu 21: Cho mch in xoay chiu khng phn nhnh c in tr hot ng bng 15 , mt cun cm thun c

t cm 2

5H v mt t in c in dung

500C F

. in p gia hai u mch in l u 75 2 cos(100t)V

lun n nh. Ghp thm t C vi C th in p hiu dng gia hai u cun cm c gi tr ln nht ULmax. Gi tr

ca C v ULmax ln lt l

A. 310

F;100V

. B. 310

F;200V

C. 310

F;200V2

D.

310F;100 2V

.

Cu 22: Cho mch in AB khng phn nhnh gm mt in tr hot ng bng 50 ; mt cun cm thun c

t cm 1

L H3

; mt t in c in dung 250

C F3

. in p xoay chiu gia A v B c tn s 60 Hz v c gi

tr hiu dng l 220 V lun khng i. Nu mc thm in tr thun R vi R th cng sut tiu th ca mch AB l

387,2 W. Gi tr ca R l

A. 60 B. 80 C. 30 D. 20

Cu 23: Cho on mch in AB gm mt in tr thun bng 40; mt t in c in dung 500

F3

; mt cun

cm c in tr hot ng 10 v c t cm L thay i c. in p xoay chiu hai u on mch c gi tr

hiu dng v tn s f = 50 Hz lun khng i. in p gia hai u cun cm lch pha 900 so vi in p hai u

mch th L phi c gi tr bng

A. 5

H hay

3

H. B.

2

H hay

1

H. C.

1

2H hay

1

10H. D.

1

2H hay

1

5H.

Cu 24: Cho on mch AB gm in tr thun R; mt t in c in dung C v mt cun cm L (theo th t )

mc ni tip. t vo AB mt in p xoay chiu c gi tr hiu dng U th in p gia hai u on mch AM (

on mch AM cha R v C) v hai u cun cm u c gi tr hiu dng bng 100 V v cng lch pha /4 so vi

dng in. in p hiu dng U bng

A. 100 2 V. B. 100 V. C. 50 2 V. D. 50 V.

Cu 25: Cho on mch RLC v mt ampe k nhit c in tr rt b mc ni tip. Bit cun cm c t cm

1

H, t in c in dung

310C F

15. in p gia hai u mch l u = U0cos(100t) V lun n nh. Khi mc

thm t in c in dung C vi C th s ch ampe k vn khng i. Gi tr ca C l

A. 310

F5

. B. 410

F5

. C. 310

F7,5

. D. 310

F75

.

Cu 26: Cho on mch in AB gm hai on mch AM v MB mc ni tip nhau. on AM gm m in tr

thun R1 mc ni tip vi t in c in dung C, on mch MB gm mt in tr thun R2 mc ni tip vi mt

cun cm thun c t cm L. t in p xoay chiu c tn s 1

f2 LC

v c gi tr hiu dng lun khng

i vo on mch AB. Khi on mch AB tiu th cng sut P1. Nu ni tt hai u cun cm th in p hai



u mch AM v MB c cng gi tr hiu dng nhng lch pha nhau /3, cng sut tiu th ca on mch AB

trong trng hp ny bng 180 W. Gi tr ca P1 l

A. 320 W. B. 360 W. C. 240 W. D. 200 W.

Cu 27: an mch AB gm mt t in C mc ni tip vi mt bin tr c gi tr t 0 n 600 . in p gia

hai u on mch ABu U 2cos(t)V. iu chnh con chy bin tr c gi tr R = 400 th cng sut ta

nhit trn bin tr ln nht v bng 100 W. Khi cng sut ta nhit trn bin tr l 80 W th bin tr c gi tr

A. 200 B. 300 C. 400 D. 500

Cu 28: t in p xoay chiu c gi tr hiu dng U = 30 2 V vo hai u on mch RLC ni tip. Bit cun

dy thun cm, c cm L thay i c. Khi in p hiu dng hai u cun dy t cc i th hiu in th

hiu dng hai u t in l 30 V. Gi tr hiu in th hiu dng cc i hai u cun dy l

A. 60 V B. 120 V C. 30 2 V D. 60 2 V

Cu 29: Cho on mch in RLC mc ni tip. Bit R l mt bin tr, cun cm thun c t cm 0,2875

H, t

in c in dung 310

F

. in p hai u mch l

u 125cos 100t V6

lun n nh. Cho R thay i. Khi R

= R1 hoc R = R2 th cng sut tiu th ca on mch u nh nhau. Bit cng dng in khi R = R1 l

1

i 4cos 100t A

4. Khi R = R2 th cng dng in qua mch l

A. 216

i cos 100t A.3 3

B. 225

i cos 100t A.7 4

C. 225

i cos 100t A.7 12

D. 216

i cos 100t A.3 12

Cu 30: Cho mch in khng phn nhnh gm mt cun cm thun; mt t in c in dung thay i c v

mt in tr hot ng bng 100 . t vo hai u mch mt in p u = 200cos(100t) V lun n nh. iu

chnh in dung ca t in in p gia hai bn t in tr pha /6 so vi u. Khi cng sut tiu th ca mch

in l

A. 75 W. B. 25 W. C. 50 W. D. 100 W.

Cu 31: t in p xoay chiu u = U0cos120t( U0 khng i, t tnh bng s) vo hai u mch in mc ni tip

gm in tr thun R, cun cm thun c t cm L thay i c v t in c in dung 2500

C F9

.iu

chnh L in p hiu dng gia hai u cun cm t gi tr cc i. Gi tr cc i bng 0U 2 . in tr R

bng

A. 40 . B. 30 . C. 10 3 . D. 10 2 .

Cu 32: Cho mt on mch xoay chiu ni tip AMB gm on mch AM (R1 ni tip C1), on mch MB (R2 =

2R1 ni tip C2). Khi ZAB = ZAM + ZMB th

A. C2 = 4C1. B. C2 = C1. C. C2 = 2C1. D. 1

2

CC

2

Cu 33: Cho on mch RLC, cun dy thun cm. t vo hai u on mch hiu in th

u 30 2cos t V. Khi cho C thay i ta thy c mt gi tr ca C lm cho UC cc i v lc thy in p

trn cun dy UL = 32 V. Gi tr cc i ca UC l

A. 30 V B. 40 V C. 50 V D. 60 V

Cu 34: on mch xoay chiu gm on AM ni tip on MB. on AM gm in tr thun R = 30 , mc ni

tip vi cun thun cm L = 0,4/ (H); on MB l mt t in c in dung thay i. t vo hai u on mch

mt in p xoay chiu c hdt hiu dng khng i, tn s 50 Hz. iu chnh in dung ca t in p hiu dng

on AM t cc i l 120V, lc in p hai u t in c gi tr:



A. 96 V B. 144 V C. 200 V D. 150 V

Cu 35: t vo hai u on mch RLC ni tip, mt in p xoay chiu c gi tr hiu dng khng i, c tn s

50 Hz. Gi tr ca cc phn t l R = 30 , L = 0,4/ (H); in dung ca t thay i c. Lc in p hiu dng

hai u t in t gi tr cc i l 150 V th in p hiu dng hai u on mch RL c gi tr bng 90 V. H s

cng sut ca on mch lc ny l:

A. 1 B. 0,8 C. 0,75 D. 0,6

Cu 36: Mch in xoay chiu RLC ghp ni tip. t in p xoay chiu c gi tr hiu dng U 100 3 V vo

hai u on mch. Khi L bin thin c mt gi tr ca L lm cho UL cc i, lc thy UC = 200 V. Hiu in th

trn cun dy thun cm t gi tr cc i bng:

A. 100 V B. 200 V C. 300 V D. 200 3 V

Cu 37: Cho mch in ni tip AB gm hai on mch AM v MB. on AM gm mt cun cm c in tr

thun v mt t in, on MB ch cha in tr thun. t vo hai u on mch AB mt in p xoay chiu c

gi tr hiu dng khng i, c tn s thay i c. Lc tn s ca in p t vo l 30 Hz v 60 Hz th in p

hiu dng hai u on mch AM c cng gi tr U1, lc tn s ca in p bng 40 Hz th in p hiu dng hai

u on AM c gi tr U2. So snh U1 v U2

A. U1 > U2 B. U1 < U2 C. U1 = U2 D. U1 = 0,5U2

Cu 38: Mt t in C c in dung thay i, ni tip vi in tr R = 10 3 v cun dy thun cm c t

cm bng 0,2

(H)

trong mch in xoay chiu tn s 50 Hz. in p hiu dng ca on mch R ni tip C l

URC t cc i th in dung C phi c gi tr sao cho dung khng bng

A. 20 B. 30 C. 40 D. 35

Cu 39: Cho on mch xoay chiu AMNB ni tip, on AM l mt cun dy, on MN l mt t in, on NB

l mt in tr thun R. t vo hai u on mch mt in p xoay chiu n nh th in p tc thi uAM lch

pha 1500 so vi uMN; uAN lch pha 30

0 so vi uMN; ng thi UAM = UNB. Lin h gia dung khng ca t v in tr

thun R?

A. C2R

Z3

B. CZ 2R C. CZ R 3 D. CZ 2R 3

Cu 40:

0,24

1

:

A. 0,577 B. 0,866 C. 0,25 D. 0,5

Cu 41: Mch in gm ng dy c 1

L (H)

mc ni tip vi t in c in dung 1

C (mF).6

Mc vo hai u

mch in p u 120 2 cos(100t)V th in p gia hai u t l CU 90 2V . Cng sut tiu th ca mch

A. 360 W B. 90 W C. 180 W D. 0 W

Cu 42: t vo hai u mt on mch in xoay chiu gm mt cun dy v mt t in mc ni tip vi in p

u 100 6 cos(100t )V.

4 in p gia hai u cun dy v hai bn t c gi tr ln lt l 100 V v 200 V. Biu

thc in p gia hai u cun dy l:

A. d

u 100 2 cos 100t V2

. B. d

u 200cos 100t V4

.

C. d3

u 200 2 cos 100t V4

. D. d3

u 100 2 cos 100t V4

.



Cu 43: Cho mch in RLC mc ni tip, cun dy thun cm v t in c in dung c th thay i c. Bit

biu thc ht gia hai u on mch uAB = 100cos(100t) V, R = 100 v 3

L (H)

. Tm gi tr cc i ca

hiu in th gia hai u t in:

A. 200 V. B. 150 V. C. 100 V. D. 250V .

Cu 44: on mch xoay chiu theo th t gm LRC ni tip, C l t in, R l in tr thun, L l cun dy thun

cm. in p xoay chiu 2 u on mch AB c dng ABu U 2cos(2ft)V . Cc in p hiu dng UC = 100

V, UL = 100 V. Cc in p uLR v uRC lch pha nhau 900. in p hiu dng UR c gi tr l

A. 100 V B. 200 V C. 150 V D. 50 V.

Cu 45: Mch in xoay chiu gm cun dy c 0,4

L H

mc ni tip vi t in C. t vo hai u on mch

in p u U 2 cos(t)V . Khi 4

1

2.10C C F

th UCmax = 100 5 V. Khi C = 2,5 C1 th cng dng in tr pha /4

so vi in p hai u on mch. Gi tr ca U l:

A. 50 V B. 100 V C. 100 2 V D. 50 5 V

Cu 46: Cho mch in RLC. in p t vo hai u on mch c dng 2L

u U 2 cos t V ; R .C

Cho bit

in p hiu dng RL RCU 3U . H s cng sut ca on mch c gi tr l

A. 2

.7

B. 3

.5

C. 3

.7

D. 2

.5

Cu 47: Cho mch in RLC, vi C thay i c. in p t vo hai u on mch c dng

u U 2 cos t V. Khi 4

1

10C C (F)

th cng dng in i tr pha /4 so vi u. Khi

4

2

10C C (F)

2,5th in p hai u t in t gi tr cc i. Tnh tn s gc , bit L = 2/ (H)?

A. 200 rad/s. B. 50 rad/s. C. 10 rad/s. D. 100 rad/s.

Cu 48: Cho mch in RLC, vi C thay i c. in p t vo hai u on mch l u 200 2 cos(t)V.

Khi C = C0 th in p hai u t in t gi tr cc i UCmax = 250 V, khi mch tiu th cng sut P = 120 W.

Tnh gi tr ca R.

A. 120 . B. 100 . C. 150 . D. 50 .

Cu 49: Cho on mch RLC, t C bin i c, cun dy cm thun. in p hai u on mch

u 78 2 cos 100t V. Khi C thay i, ta thy c hai gi tr 2 4

1 2

10 10C C (F) ; C C (F)

28 th in p hiu

dng gia hai u in tr R v hai u cun cm c cng gi tr l 62,4 V. Gi tr ca R v L l

A. 6,4

50 ; (H).

B. 0,64

48 ; (H).

C. 4,6

60 ; (H).

D.

6,430 ; (H).

Cu 50: on mch in gm 1 cun dy c in tr R v t cm L ni tip vi mt t in c in dung thay

i c. in p xoay chiu 2 u on mch l u U 2 cos t V . Khi C = C1 th cng sut ca mch l P =

200 W v cng dng in wa mch l

i I 2 cos t A.3

Khi C = C2 th cng sut cc i, gi tr cc i

l

A. 400 W. B. 200 W. C. 800 W. D. 600 W.



Cu 51: Cho on mch RLC. in p hai u on mch u 150 2 cos 100t V. Khi in dung t in

3

1

10C C (F)

16th mch tiu th cng sut cc i Pmax = 93,75 W. Khi in dung t in

3

2

10C C (F)

thi

in p gia hai u RC v in p gia hai u cun dy vung pha vi nhau. Tnh in p hiu dng gia hai u

RC v hai u cun dy ng vi gi tr C2.

A. URC = 90 V ; Ud = 120 V. B. URC = 100 V ; Ud = 150 V.

C. URC = 150 V ; Ud = 120 V. D. URC = 70 V ; Ud = 90 V.

Cu 52: Mt mch in xoay chiu khng phn nhnh c R = 10 , cun dy thun cm c t cm 1

L H10

v t in 500

C F

. Bit biu thc ca ht gia hai u cun dy c dng L

u 100 2cos 100t V4

. Biu

thc ca hiu in th gia hai u on mch l

A. u = 200cos(100t + /4) V B. u = 100 2 cos(100t 3/4) V

C. u = 200 2 cos(100t 3/4) V D. u = 200cos(100t 3/4) V

Cu 53: t hiu in th xoay chiu c f thay i vo hai u on mch in xoay chiu RLC mc theo th t

c 21 10

R 50 ; L (H);C (F).6 24

hiu in p hiu dng 2 u LC (ULC) t gi tr cc tiu th tn s dng

in phi bng

A. 60 Hz. B. 50 Hz. C. 55 Hz. D. 40 Hz.

Cu 54: Cho mch in xoay chiu ch cha t in. Hiu in th hai u on mch c dng u = U0sin(2ft) V.

Ti thi im t1 gi tr tc thi ca cng dng in qua t v hiu in th hai u on mch l

2 2A;60 6V . Ti thi im t2 gi tr tc thi ca cng dng in qua t v hiu in th hai u on mch

l 2 6A;60 2V . Dung khng ca t in bng

A. 20 2 B. 20 3 C. 30 D. 40

Cu 55: Cho mch in xoay chiu RLC. Cun dy thun cm 40,3 4.10

L H;C F

; R l bin tr. t mch

vo hiu in th u 200 2 cos 100t V

a) Vit biu thc uR khi cng sut ca mch t cc i

A. R

u 200cos 100t V.4

B. R

u 200cos 100t V.4

C. R

u 100cos 100t V.4

D. R

u 100 2 cos 100t V.4

Cu 56: Cho on mch in AB khng phn nhnh gm cun cm thun, t in c in dung thay i c, mt

in tr hot ng 100 . Gia A, B c mt in p xoay chiu n nh

u 110cos 120t V3

. Cho C thay i.

Khi 125

C F3

th in p hiu dng gia hai u cun c gi tr ln nht. Biu thc ca in p gia hai u cun

cm l

A. L

u 220cos 120t V.2

B. L

u 110 2 cos 120t V.2

C. L

u 220cos 120t V.6

D. L

u 110 2 cos 120t V.6



Cu 57: Mch RLC c 2L

RC

v tn s thay i c. Khi f = f1 hoc f = f2 th mch c cng h s cng sut.

Bit f2 = 2f1. H s cng sut ca mch khi l

A. 3

.6

B. 6

.3

C. 2

.6

D. 6

.13

Cu 58: Cho mch in xoay chiu RLC mc ni tip, R l bin tr. t vo hai u on mch mt in p xoay

chiu n nh u U 2 cos(t)V . Khi thay i gi tr ca bin tr ta thy c hai gi tr R = R1 = 45 hoc R=R2 =

80 th tiu th cng cng sut P. H s cng sut ca on mch in ng vi hai tr ca bin tr R1, R2 l

A. cos1 = 0,5; cos2 = 1. B. cos1 = 0,5; cos2 = 0,8.

C. cos1 = 0,8; cos2 = 0,6. D. cos1 = 0,6; cos2 = 0,8.

Cu 59: Cho mch in RLC. in p t vo hai u on mch c dng 2L

u U 2 cos t V ; R .C

Cho bit

in p hiu dng RL RCU 5U . H s cng sut ca on mch c gi tr l

A. 21

.5

B. 5

.21

C. 3

.7

D. 5

.21

Cu 60: Cho on mch in AB khng phn nhnh mc theo th t :mt cun cm ,mt t in c in dung C

thay i c ,mt in tr thun R = 50 .Gia A,B c mt in p xoay chiu lun n nh u 164 2 cos(t) V.

Cho C thay i .Khi dung khng ca t in bng 40 th in p gia hai u cun cm lch pha /2 so vi in

p gia hai u mch MB (on mch MB cha C v R) v cng sut tiu th ca mch AB ln nht Pmax.Gi tr

ca Pmax bng

A. 328,00 W B. 840,50 W C. 672,50 W D. 537,92 W

Cu 61: Cho mch RLC ni tip. in p xoay chiu gia hai u on mch l u 120 2 cos(100t)V . t cm

L ca cun dy thun cm thay i c. iu chnh L th thy khi 0,4

L H

th in p hiu dng gia bn t cc

i bng 80 3 V. in tr R ca mch c gi tr

A. 10 . B. 10 3 . C. 20 3 . D. 15 .

Cu 62: Cho mch in AB khng phn nhnh gm mt in tr hot ng bng 50 ; mt cun cm thun c

t cm 1

L H3

; mt t in c in dung 250

C F3

. in p xoay chiu gia A v B c tn s 60 Hz v c gi

tr hiu dng l 220 V lun khng i. Nu mc thm in tr thun R vi R th cng sut tiu th ca mch AB l

387,2 W. Gi tr ca R l

A. 60 B. 80 C. 30 D. 20

Cu 63: Mch in xoay chiu khng phn nhnh gm in tr thun R, cun cm thun c cm khng ZL v t

in c dung khng C LZ 2Z . Vo mt thi im khi hiu in th trn in tr v trn t in c gi tr tc thi

tng ng l 40 V v 30 V th hiu in th gia hai u mch in l

A. 55 V B. 85 V C. 50 V D. 25 V

Cu 64: Mt my pht in xoay chiu mt pha truyn i mt cng sut in khng i. Khi in p hiu dng hai

u ng dy l U th hiu sut truyn ti l 84%. hiu sut truyn ti tng thm 12% th in p hiu dng hai

u ng dy phi l

A. 4 U. B. 2,5U. C. 2,25U. D. 2U.

Cu 65: Mt trm pht in xoay chiu c cng sut khng i, truyn in i xa vi in p hai u dy ti ni

truyn i l 200 kV th tn hao in nng l 25%. Nu tng in p truyn ti ln 500 kV th tn hao in nng l

A. 12% B. 75% C. 4% D. 4,8%

Cu 66: Mt nh my pht in c cng sut 36 MW, hiu in th hai cc my pht 4 kV. Ngi ta ni hai cc

my pht vi cun s cp ca my tng th, s vng dy ca cun th cp ca my bin th gp 50 ln s vng dy



ca cun s cp. Hiu sut ca my bin th l 90%. Bit h s cng sut cun th cp l 0,9. Xc nh dng in

hiu dng nhn c cun th cp?

A. 180 A B. 160 A C. 140 A D. 120 A

Cu 67: in nng c ti t trm tng p ti trm h p bng ng dy ti in mt pha c in tr R = 50 .

Bit in p hiu dng hai u cun s cp v th cp ca my h p ln lt l 2200 V v 220 V, cng dng

in chy trong cun th cp ca my h p l 100 A. B qua tn hao nng lng cc my bin p. Coi h s

cng sut bng 1. in p hiu dng hai u cun th cp ca my tng p l

A. 2700 V. B. 2420 V. C. 2200 V. D. 4400 V.

Cu 68: Ngi ta truyn ti dng in xoay chiu mt pha t nh my in n ni tiu th. Khi in p nh my

in l 6kV th hiu sut truyn ti l 73%. hiu sut truyn ti l 97% th in p nh my in l

A. 486 kV. B. 18 kV. C. 48,6 kV. D. 54 kV.

Cu 69: Trong qu trnh truyn ti in nng i xa, cui ngun khng dng my h th. Cn phi tng in p ca

ngun ln bao nhiu ln gim cng sut hao ph trn ng dy 100 ln nhng vn m bo cng sut ni tiu

th nhn c l khng i. Bit in p tc thi u cng pha vi dng in tc thi i v ban u gim in p

trn ng dy bng 10% in p ca ti tiu th

A. 9,1 ln. B. 10 ln. C. 10 ln. D. 9,78 ln.

Cu 70: Trong gi hc thc hnh, hc sinh mc ni tip mt qut in xoay chiu vi in tr R ri mc hai u on mch ny vo in p xoay chiu c gi tr hiu dng 380 V. Bit qut in ny c cc gi tr nh mc: 220V 88 W v khi hot ng ng cng sut nh mc th lch pha gia in p hai u qut v cng dng in qua n l , vi cos = 0,8. qut in ny chy ng cng sut nh mc th R bng A. 361 . B. 180 . C. 267 . D. 354 . Cu 71: Mt ng c in c ghi 220V-176W, h s cng sut bng 0,8 c mc vo mch in xoay chiu c

in p hiu dng 380V. ng c hot ng bnh thng, phi mc ng c ni tip vi mt in tr thun c

gi tr:

A. 180 B. 300 C. 220 D. 176

Cu 72: Mt on mch gm in tr thun R = 200 mc ni tip vi t in C. Ni 2 u on mch vi 2 cc

ca mt my pht in xoay chiu mt pha, b qua in tr cc cun dy trong my pht. Khi rto ca my quay

u vi tc 200 vng/pht th cng dng in hiu dng trong on mch l I . Khi rto ca my quay u

vi tc 400 vng/pht th cng dng in hiu dng trong on mch l 2 2 I. Nu rto ca my quay u

vi tc 800 vng/pht th dung khng ca on mch l

A. ZC = 100 2 . B. ZC = 200 2 . C. ZC = 800 2 . D. ZC = 50 2 .

Cu 73: Mt my bin th c hiu sut xp x bng 100%, c s vng dy cun s cp gp 10 ln s vng dy cun

th cp. My bin th ny

A. lm gim tn s dng in cun s cp 10 ln.

B. lm tng tn s dng in cun s cp 10 ln.

C. l my h th.

D. l my tng th.

Cu 74: Mt my bin p l tng c cun s cp gm 2000 vng v cun th cp gm 100 vng. in p v

cng mch s cp l 220 V; 0,8 A. in p v cng dng in cun th cp l

A. 11 V; 0,04 A. B. 1100 V; 0,04 A. C. 11 V; 16 A. D. 22 V; 16 A.

Cu 75: Mt my bin th dng trong my thu v tuyn c cun s cp gm 1000 vng, mc vo mng in 27 V

v ba cun th cp ly ra cc hiu in th 6,35 V; 15 V; 18,5 V. S vng dy ca mi cun th cp ln lt l:

A. 71 vng, 167 vng, 207 vng B. 71 vng, 167 vng, 146 vng

C. 50 vng, 118 vng, 146 vng D.71 vng, 118 vng, 207 vng

Cu 76: Mt my bin p , cun s cp c 500 vng dy, cun th cp c 50 vng dy. in p hiu dng hai u

cun s cp l 100V. Hiu sut ca my bin p l 95%. Mch th cp l mt bng n dy tc tiu th cng sut

25 W. in p hiu dng c hai u cun th cp l



A. 100 V. B. 1000 V. C. 10 V. D. 200 V.

Cu 77: Mt my bin p c cun s cp gm 2000 vng, cun th cp gm 100 vng. in p v cng dng

in mch s cp l 120V v 0,8A. in p v cng sut cun th cp l

A. 6 V; 96 W. B. 240 V; 96 W. C. 6 V; 4,8 W. D. 120 V; 48 W.

Cu 78: Mt my bin th gm cun s cp c 2500 vng dy, cun th cp c 100 vng dy. in p hiu dng

hai u cun s cp l 220 V. in p hiu dng hai u cun th cp l.

A. 5,5 V. B. 8,8 V. C. 16 V. D. 11 V.

Cu 79: Cun s cp ca my bin p mc qua ampe k vo in p xoay chiu c gi tr hiu dng 100V th ampe

k ch 0,0125 A. Bit cun th cp mc vo mch gm mt nam chm in c r = 1 v mt in tr R = 9 . T

s gia vng dy cun s cp v cun th cp bng 20. B qua hao ph. lch pha gia cng dng in v

in p cun th cp l?

A. /4. B. /4. C. /2. D. /3.

Cu 80: Mt my bin p, cun s cp c 500 vng dy, cun th cp c 50 vng dy. in p hiu dng hai u

cun s cp l 100 V. Hiu sut ca my bin p l 95%. Mch th cp l mt bng n dy tc tiu th cng sut

25W. Cng dng in mch s cp bng (coi h s cng sut trong cun s cp bng 1):

A. 2,63A. B. 0,236 A. C. 0,623A. D. 0,263A.

Cu 81: Mt my bin th c s vng cun s cp v th cp ln lt l 2200 vng v 120 vng. Mc cun s cp

vi mng in xoay chiu 220 V 50 Hz, khi hiu in th hiu dng gia hai u cun th cp h l

A. 24 V. B. 17 V. C. 12 V. D. 8,5 V.

Cu 82: Mt my pht in xoay chiu c cng sut 1000 kW. Dng in n pht ra sau khi tng in p ln n

110 kV c truyn i xa bng mt ng dy c in tr 20 . Cng sut hao ph trn ng dy l

A. 6050 W. B. 5500 W. C. 2420 W. D. 1653 W.

Cu 83: Mt dng in xoay chiu mt pha, cng sut 500 kW c truyn bng ng dy dn c in tr tng

cng l 4 . Hiu in th ngun in lc pht ra U = 5000 V. H s cng sut ca ng dy ti l cos = 0,8.

C bao nhiu phn trm cng sut b mt mt trn ng dy ti in do to nhit?

A. 10% B. 20% C. 25% D. 12,5%

Cu 84: Cng sut truyn i ca mt trm pht in l 200 kW. Hiu s ch ca cc cng t in trm pht v

ni thu sau mt ngy m lch nhau thm 480 kWh. Hiu sut ti in l.

A. 70 % B. 80 % C. 90 % D. 95 %

Cu 85: Mt trm in cn truyn ti in nng i xa. Nu hiu in th trm pht l U1 = 5 kV th hiu sut ti

in l 80%. Nu dng mt my bin th tng hiu in th trm pht ln U2 = 5 2 kV th hiu sut ti in khi

l:

A. 85% B. 90% C. 95% D. 92%

Cu 86: Cn truyn i mt cng sut in 1200 kW theo mt ng dy ti in c in tr l 20. Tnh cng sut

hao ph dc ng dy ti in khi ng dy ti in c in p 40 kV.

A. 18 kW. B. 36 kW. C. 12 kW. D. 24 kW.

Cu 87: Mt my pht in ngi ta mun truyn ti ni tiu th mt cng sut in l 196 KW vi hiu sut

truyn ti l 98%. Bit in tr ca ng dy ti l 40 . Cn phi a ln ng dy ti ti ni t my pht in

mt in p bng bao nhiu?

A. 10 kV. B. 20 kV. C. 40 kV. D. 30 kV

Cu 88: truyn cng sut in P = 40 kW i xa t ni c in p U1 = 2000 V, ngi ta dng dy dn bng

ng, bit in p ni cui ng dy l U2 = 1800 V. in tr dy l

A. 50 . B. 40 . C. 10 . D. 1 .

Cu 89: Ta cn truyn mt cng sut in 1 MW di mt in p hiu dng 10 kV i xa bng ng dy mt pha.

Mch c h s cng sut cos = 0,8. Mun cho t l nng lng mt mt trn ng dy khng qu 10% th in

tr ca ng dy phi c gi tr l

A. R 6,4 . B. R 3,2 . C. R 6,4 k. D. R 3,2 k.



Cu 90: Cn truyn ti in nng t A n B cch nhau 10 km, ti A c in p 100 kV v cng sut 5000 W, in

tr ca ng dy ti bng ng l R. Bit gim in th trn ng dy ti khng vt qu 1%. Cho in tr

sut ca ng l 1,7.10-8 .m. in tr R c th t gi tr ti a v tit din nh nht ca dy ng bng

A. 20 , 17 mm2. B. 17 ; 9,8 mm2. C. 20 ; 8,5 mm2. D. 10 ; 7,5 mm2

Cu 91: Mt my pht in xoay chiu mt pha cu to gm nam chm c 5 cp cc quay vi tc 24 vng/giy.

Tn s ca dng in l

A. 120 Hz. B. 60 Hz. C. 50 Hz. D. 2 Hz.

Cu 92: Mt my pht in xoay chiu c hai cp cc, rto quay mi pht 1800 vng. Mt my pht in khc c 6

cp cc, n phi quay vi vn tc bng bao nhiu pht ra dng in cng tn s vi my th nht?

A. 600 vng/pht. B. 300 vng/pht. C. 240 vng/pht. D.120 vng/pht.

Cu 93: Mt my pht in xoay chiu mt pha c phn cm l rto gm 10 cp cc (10 cc nam v 10 cc bc).

Rto quay vi tc 300 vng/pht. Sut in ng do my sinh ra c tn s bng

A. 3000 Hz. B. 50 Hz. C. 5 Hz. D. 30 Hz.

Cu 94: Mt my pht in m phn cm gm hai cp cc t quay vi tc 1500 vng/pht v phn ng gm hai

cun dy mc ni tip, c sut in ng hiu dng 220 V, t thng cc i qua mi vng dy l 5 mWb. Mi cun

dy phn ng gm bao nhiu vng ?

A. 198 vng. B. 99 vng. C. 140 vng. D. 70 vng.

Cu 95: Mt my dao in mt pha c stato gm 8 cun dy ni tip v rto 8 cc quay u vi vn tc 750

vng/pht, to ra sut in ng hiu dng 220V. T thng cc i qua mi vng dy l 4 mWb. S vng ca mi

cun dy l

A. 25 vng. B. 28 vng. C. 31 vng. D. 35 vng

Cu 96: t in p xoay chiu c gi tr hiu dng U = 30 2 V vo hai u on mch RLC ni tip. Bit cun

dy thun cm, c cm L thay i c. Khi in p hiu dng hai u cun dy t cc i th hiu in th

hiu dng hai u t in l 30V. Gi tr hiu in th hiu dng cc i hai u cun dy l:

A. 60V B. 120V C. 30 2 V D. 60 2 V

Cu 97: Cho mch in xoay chiu AB gm R, L, C mc ni tip. Cun cm thun c t cm thay i c. t

vo hai u on mch AB mt in p xoay chiu n nh )V()t100cos(6100u . iu chnh t cm

in p hiu dng hai u cun cm t gi tr cc i l maxLU th UC =200 V. Gi tr maxLU l

A. 100 V. B. 150 V. C. 300 V. D. 250 V.

Cu 98. C hai my bin p l tng (b qua mi hao ph) cun s cp c cng s vng dy nhng cun th cp c

s vng dy khc nhau. Khi t in p xoay chiu c gi tr hiu dng U khng i vo hai u cun th cp ca

my th nht th t s gia in p hiu dng hai u cun th cp h v cun s cp ca my l 1,5. Khi

t in p xoay chiu ni trn vo hai u cun s cp ca my th hai th t s l 1,8. Khi cng thay i s

vng dy ca cun th cp ca mi my 48 vng dy ri lp li th nghim th t s in p ni trn ca hai my l

bng nhau. S vng dy ca cun s cp ca mi my l

A. 300 vng B. 440 vng C. 250 vng D. 320 vng

Cu 99. in p gia 2 cc ca my pht in cn tng ln bao nhiu ln cng sut hao ph gim 90 ln vi iu

kin cng sut truyn n ti tiu thu khng i v khi cha tng thi gim in p trn ng dy bng 5% in

gia hai cc my pht. Coi cng dng in lun cng pha vi in p.

A. 9,02 ln B. 8,82 ln. C. 9,22 ln. D. 9,12 ln.

Cu 100. Cho on mch xoay chiu gm in tr thun, cun dy thun cm v t in mc ni tip vi nhau. T

in c in dung thay i c. t vo hai u on mch mt in p xoay chiu c gi tr hiu dng l 200 V,

tn s 50 Hz. iu chnh in dung ca t in in p hiu dng gia hai bn t t cc i, khi cng

dng in tc thi trong mch c gi tr hiu dng 2 A v lch pha so vi in p hai u on mch l /3 rad. Gi

tr in dung ca t in l



A. 410

(F). 3

B. 42.10

(F). 3

C. 43.10

(F).2

D. 43.10

(F).

Cu 101. on mch xoay chiu gm mt cun dy c cm khng ZL mc ni tip vi in tr thun R. in p

hiu dng hai u cun dy, hai u in tr R, hai u on mch tng ng l U1, UR, U. in p hai u cun

dy lch pha /3 so vi in p hai u in tr R v U1 = UR. Gi cng sut mch l P. Kt lun no sau y sai?

A. 2U

P .2R

B. RU 3U . C. 3

cos .2

D. LZ 3R.

Gio vin: ng Vit Hng

Ngun : Hocmai.vn

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Thay Dang Viet Hung - 101 Cau Trac Nghiem Dien Xoay Chieu Hay Va Kho-V2