1.I CNG V DNG IN XOAY CHIU Cu 1: Gi tr hiu dng ca dng in xoay chiu c biu thc i = 2 3 cos200 t(A) l A. 2A. D. 3 2 A. Cu 2: Gi tr hiu dng ca in p xoay chiu c biu thc u = 220 5 cos100 t(V) l A. 220 5 V. B. 220V. C. 110 10 V. D. 110 5 V. Cu 3(C-2009): in p gia hai u mt on mch l u = 150cos100 t (V). C mi giy c bao nhiu ln in p ny bng khng? A. 100 ln. B. 50 ln. C. 200 ln. D. 2 ln. t) n v Ampe, giy. Hi trong mt giy k t lc t = 0 Cu 4: Mt dng in xoay chiu c biu thc i = 2 2 cos(100 dng in tc thi t gi tr 2A bao nhiu ln. A. 200 ln. B. 100 ln C. 50 ln D. 10 ln. t Cu 5: Dng in xoay chiu chy qua mt on mch c biu thc i =2 2 cos( 100 )( A) , t tnh bng giy 1 (s).Vo thi im t = (s) th dng in chy trong on mch c cng tc thi bng 300 A. 1,0 A v ang tng . B. 2 A v ang gim. C. 1,0 A v ang gim . D. 2 A v ang tng Cu 6: dng in chy qua mt am pe k c Biu thc ca cng dng in xoay chiu trong mt on mch l i = 5cos(100 t + /3)(A). thi im t = 1s s ch ca am pe k l A. 5A. B. 2,5 2 A. C. 2,5V . D. 0. Cu 7 : in p gia hai bn t in c biu thc u = U 0 cos(100t / 3) (V). Xc nh thi im m cng dng in qua t bng 0 ln th nht l A. 1/600s. B. 1/300s. C. 1/150s. D. 5/600s. Cu 8(H 2007): Dng in chy qua mt on mch c biu thc i = I0cos100t. Trong khong thi gian t 0 n 0,01s cng dng in tc thi c gi tr bng 0,5I0 vo nhng thi im A. 1/300s v 2/300. s B.1/400 s v 2/400. s C. 1/500 s v 3/500. S D. 1/600 s v 5/600. s Cu 9 : Mt dng in xoay chiu c tn s 60Hz v cng hiu dng 2A. Vo thi im t = 0, cng dng in bng 2A v sau tng dn. Biu thc ca dng in tc thi l: A. i = 2 2 cos(120 t + ). B. i = 2 2 cos(120 t). C. i = 2 2 cos(120 t Cu 10(H - 2010): Ti thi im t, in p u = 200 2 cos(100 t tr 100 2V v ang gim. Sau thi im A. 100V. B. 100 3V . B. 2 3 A. C.

6 A.

) (trong u tnh bng V, t tnh bng s) c gi 2

). D. i = 2 2 cos(120 t + ). 4 4

1 s , in p ny c gi tr l 300 C. 100 2V .

D. 200 V.

Cu 11: th biu din s ph thuc cng dng in theo thi gian ca on mch xoay chiu ch c t in vi ZC=25 cho hnh v. Biu thc in p hai u on mch l: A. u=50 2cos(100t+ ) v. B. u=50cos(100t+ ) v. 6 6 C. u=50cos(100t- ) v. D. u=50 2cos(100t- ) 3 3 Cu 12: Dng in xoay chiu c th nh hnh v Vit phng trnh dng in tc thi. A. i = 0,004cos(1000 t C. i = 4cos( t +

I(A) 2 1

) 2

) 4

B. i = 0,004cos(106 t D. i = 0,004cos( t +

) 6

) 3

Cu 13: Mc mt n non vo ngun in xoay chiu c in p l u = 220 2 sin(100 t)V. n ch pht sng khi in p t vo n tho mn h thc U 220 A. t =

3 2

V. Khong thi gian n sng trong 1 chu k l

2 1 1 1 s B. t = s C. t = s D. t = s 300 300 150 200 Cu 14: Mt bng n Neon ch sng khi t vo hai u bng n mt in p u 155V. t vo hai u bng n in p xoay chiu c gi tr hiu dng U = 220V. Thy rng trong mt chu k ca dng in thi gian n sng l 1/75(s). Tn s ca dng in xoay chiu l: A. 60Hz. B. 50Hz. C. 100Hz. D. 75Hz. Cu 15: Mt n in c ghi 110 V- 100 W mc ni tip vi mt in tr R vo mt mch in xoay chiu c U = 220 cos(100 t) (V). n sng bnh thng, in tr R phi c gi tr A. 121 . B. 1210 . C. 110 . D.

100 11

Cu16: Mt n c ghi 100V 100W mc ni tip vi in tr t vo mt mch in xoay chiu c u = 200 2 cos(100 t ) (V). n sng bnh thng , dung khng phi c gi tr bng A. 1210 . B. 10/11 . C. 121 . D. kt qu khc Cu 17 : Mt dng in xoay chiu i qua mt in tr R = 50 () nhng trong mt nhit lng k cha 1 lt nc. Sau 7 pht, nhit ca nhit lng k tng 100C, nhit dung ring ca nc C = 4200 J/kg. Xc nh cng cc i ca dng in? A. 2 A B.2 2 A C.2 A D.1 A Cu 18: Nhit lng Q do dng in c biu thc i = 2cos120 t(A) to ra khi i qua in tr R = 10 trong thi gian t = 0,5 pht l A. 1000J. B. 600J. C. 400J. D. 200J. Cu 19 : Mt dng in xoay chiu i qua in tr R = 25 trong thi gian 2 pht th nhit lng to ra l Q = 6000J. Cng hiu dng ca dng in xoay chiu l A. 3A. B. 2A. C. 3 A. D. 2 A. Cu 20 : Dng in xoay chiu hnh sin chy qua mt on mch c biu thc cng dng in l i = Iocos t. in lng chuyn qua tit din thng ca dy dn trong 1/4 chu k l: A.

Cu 21: Mt dng in xoay chiu c cng hiu dng l I c tn s l f th in lng qua tit din ca dy trong thi gian mt na chu k k t khi dng in bng khng l : A.

I oT 2

B.

I oT 2I f

C.

2 I oT 3

D.

I oT 4

I 2 f

B.

C.

f I 2

D.

f 2I

Cu 22: Khi quay u mt khung dy xung quanh mt trc t trong mt t trng u c vect cm ng t B vung gc vi trc quay ca khung, t thng xuyn qua khung dy c biu thc = 2.10-2cos(720t + sut in ng cm ng trong khung l A. e = 14,4sin(720t 14,4sin(720t +

)Wb. Biu thc ca 66

3

)V

B. e = -14,4sin(720t +

3

)V C. e = 144sin(720t -

)V D. e =

)V 6 Cu 23(H 2008): Mt khung dy dn hnh ch nht c 100 vng, din tch mi vng 600 cm 2, quay u quanh trc i xng ca khung vi vn tc gc 120 vng/pht trong mt t trng u c cm ng t bng 0,2T. Trc quay vung gc vi cc ng cm ng t. Chn gc thi gian lc vect php tuyn ca mt phng khung dy ngc hng vi vect cm ng t. Biu thc sut in ng cm ng trong khung l A. e = 48 sin(40t ) (V).

2

B. e = 4,8 sin(4t + ) (V).

C. e = 48 sin(4t + ) (V).

D. e = 4,8 sin(40t ) (V).

2

Cu 24: Chn cu tr li ng. Mt khung dy dn c din tch S = 50cm2 gm 250 vng dy quay u vi vn tc 3000 vng/min trong mt t trng u B trc quay v c ln B = 0,02T. T thng cc i gi qua khung l A. 0,025Wb. B. 0,15Wb. C. 1,5Wb. D. 15Wb. Cu 25(CAO NG 2010): Mt khung dy dn phng dt hnh ch nht c 500 vng dy, din tch mi vng l 220 cm2. Khung quay u vi tc 50 vng/giy quanh mt trc i xng nm trong mt phng ca khung dy, trong mt t trng u c vc t cm ng t B vung gc vi trc quay v c ln bng A. 110 2 V. B. 220 2 V. C. 110 V.

u r

2 T. Sut in ng cc i trong khung dy 5D. 220 V.

Cu 26: Mt khung dy quay u trong t trng u quanh mt trc vung gc vi ng cm ng t. Sut in ng hiu dng trong khung l 60V. Nu gim tc quay i 2 ln nhng tng cm ng t ln 3 ln th sut in ng hiu dng trong khung c gi tr l: A. 60V. B. 90V. C. 120V. D. 150V. 2.ON MCH CHI C R , hoc CH C L, hoc CH C C Cu 1: t in p xoay chiu u = U0cos t vo hai u on mch ch c t in. Bit t in c in dung C. Biu thc cng dng in trong mch l ). D. i = CU0cos t. 2 2 Cu 2(H - 2010): t in ap u = U0cos t vao hai u cun cam thun co t cam L thi cng dong in qua cun cam la A. i = A. i = CU0cos( t -

). B. i = CU0cos( t + ). C. i = CU0cos( t +

U0 cos(t + ) L 2

B. i =

U0 U cos(t + ) C. i = 0 cos(t ) 2 L 2 L 2

D. i =

U0 cos(t ) 2 L 2

Cu 3(CAO NG 2010): t in p xoay chiu u=U0cos t vo hai u on mch ch c in tr thun. Gi U l in p hiu dng gia hai u on mch; i, I 0 v I ln lt l gi tr tc thi, gi tr cc i v gi tr hiu dng ca cng dng in trong on mch. H thc no sau y sai?

U I u2 i2 u i + = 2. =0. C. D. 2 + 2 = 1 . U 0 I0 U 0 I0 U I Cu 4 : Mt t in c in dung C = 31,8 F. in p hiu dng hai u bn t khi c dng in xoay chiu c tn sA. B. 50Hz v cng dng in cc i 2 2 A chy qua n l A. 200 2 V. B. 200V. C. 20V. D. 20 2 V. Cu 5: Mt cun dy dn in tr khng ng k c cun di v ni vo mng in xoay chiu 127V 50Hz. Dng in cc i qua n bng 10A. t cm ca cun dy l A. 0,04H. B. 0,08H. C. 0,057H. D. 0,114H. Cu 6: Mt cun dy c t cm L v in tr thun khng ng k, mc vo mng in xoay chiu tn s 60Hz th cng dng in qua cun dy l 12A. Nu mc cun dy trn vo mng in xoay chiu c tn s 1000Hz th cng dng in qua cun dy l A. 0,72A. B. 200A. C. 1,4A. D. 0,005A. Cu 7: t mt in p xoay chiu c gi tr hiu dng U khng i v tn s 50 Hz vo hai bn ca mt t in th cng dng in hiu dng qua t l 2 A . cng dng in hiu dng qua t bng 1 A th tn s dng in l A. 200 Hz . B. 100 Hz . C. 50 Hz . D. 25 Hz . Cu 8: on mch in xoay chiu AB ch cha mt trong cc phn t: in tr thun, cun dy hoc t in. Khi t in p u = U0cos( t - /6) ln hai u A v B th dng in trong mch c biu thc i = I 0cos( t + /3). on mch AB cha A. in tr thun B. cun dy c in tr thun C. cun dy thun cm D. t in

U I =0. U 0 I0

Cu 9 : t vo hai u t in C c in dung khng i mt in p u=U0cos100 t (V). Khi u= -50 V u=50 V th i= - A. in p U0 c gi tr l: A. 50 V. B. 100 V. C. 50 V. D. 100 V Cu 10(H 2009): t in p u = U 0 cos 100 t

th i= A, khi

im in p gia hai u t in l 150 V th cng dng in trong mch l 4A. Biu thc ca cng dng in trong mch l A. i = 4 2 cos 100 t +

2.104 (V) vo hai u mt t in c in dung (F). thi 3

(A) 6 C. i = 5cos 100 t (A) D. i = 4 2 cos 100 t (A) 6 6 Cu 11(H 2009): t in p xoay chiu u = U 0 cos 100 t + (V ) vo hai u mt cun cm thun c t cm 3 1 L= (H). thi im in p gia hai u cun cm l 100 2 V th cng dng in qua cun cm l 2A. Biu 2 B. i = 5cos 100 t + thc ca cng dng in qua cun cm l

(A). 6

( A) 6 C. i = 2 2 cos 100 t + ( A) 6 A. i = 2 3 cos 100 t

( A) 6 D. i = 2 2 cos 100 t ( A) 6 B. i = 2 3 cos 100 t +

Quan h v pha- Biu thc u v iCu 1(H 2009): Khi t in p khng i 30 V vo hai u on mch gm in tr thun mc ni tip vi cun cm thun c t cm (H) th dng in trong on mch l dng in mt chiu c cng 1 A. Nu t vo hai u cos120t (V) th biu thc ca cng dng in trong on mch l B. i=5 cos(120t ) (A)

on mch ny in p u=150 A. i=5 cos(120t + ) (A).

C. i=5cos(120t +

) (A).

D. i=5cos(120t-

) (A).

Cu 2 : Mt mch in khng phn nhnh gm 3 phn t: R = 80 , C = 10-4/2 (F) v cun dy L = 1/ (H), in tr r = 20 . Dng in xoay chiu trong mch l : i = 2cos(100 t - /6)(A). in p tc thi gia hai u on mch l A. u = 200cos(100 t - /4)(V). B. u = 200 2 cos(100 t - /4)(V). C. u = 200 2 cos(100 t -5 /12)(V).D. u = 200cos(100 t -5 /12)(V). Cu 3 : Mt on mch gm t in C c dung khng ZC = 100 v mt cun dy c cm khng ZL = 200 mc ni tip nhau. in p ti hai u cun cm c biu thc u L = 100cos(100 t + /6)(V). Biu thc in p hai u t in c dng nh th no? A. uC = 50cos(100 t - /3)(V). B. uC = 50cos(100 t - 5 /6)(V). t - /2)(V). C. uC = 100cos(100 D.. uC = 100cos(100 t + /6)(V). Cu 4: Nu t vo hai u mt mch in cha mt in tr thun v mt t in mc ni tip mt in p xoay chiu c biu thc u =U0cos( t gia hai bn t s l A. uC = I0 .R cos( t -

) (V), khi dng in trong mch c biu thc i=I0cos( t - ) (A). Biu thc in p 2 4

U 3 )(V). B. uC = 0 cos( t + )(V). 4 R 4

C. uC = I0.ZC cos( t +

)(V). 4

D. uC = I0 .R cos( t -

)(V). 2

Cu 5: t in p xoay chiu c gi tr hiu dng 60V vo hai u on mch R, L, C mc ni tip th cng dng in qua on mch l i1 = I 0 cos 100 .t + (A). Nu ngt b t in C th cng dng in qua on mch l 2 i2 = I 0 cos 100 .t (A). in p hai u on mch l 6 A. u = 60 2 cos (100 .t / 3) (V). B. u = 60 2 cos (100 .t / 6 ) (V) C. u = 60 2 cos (100 .t + / 3) (V). D. u = 60 2 cos (100 .t + / 6 ) (V). Cu 6: Khi t in p khng i 30V vo hai u on mch gm in tr thun mc ni tip vi cun cm thun c

1 (H) th dng in trong on mch l dng in mt chiu c cng 1 A. Nu t vo hai u on mch 4 ny in p u = 150 2 cos120t (V) th biu thc ca cng dng in trong on mch l A. i = 5 2 cos(120t ) (A). B. i = 5cos(120t + ) (A). 4 4 C. i = 5 2 cos(120t + ) (A). D. i = 5cos(120t ) (A). 4 4t cm Cu 7(H 2009): t in p xoay chiu vo hai u on mch c R, L, C mc ni tip. Bit R = 10 , cun cm thun c L=1/(10) (H), t in c C = (F) v in p gia hai u cun cm thun l u L= 20 B. u = 40 cos(100t /4) (V). cos(100t + /2)

(V). Biu thc in p gia hai u on mch l A. u = 40cos(100t + /4) (V). C. u = 40 cos(100t + /4) (V).

D. u = 40cos(100t /4) (V).

BI TON NGC :1 2.10 4 (H), t in c in dung C = (F). Chu k ca dng in xoay chiu trong mch l 0,02s. Cng dng in trong mch lch pha so vi in p 6Cu 1: Mt mch in gm R,L,C mc ni tip. Cun cm c t cm L = hai u mch th in tr R c gi tr l 1 00 50 A. B. 100 3 C. 50 3 D. 3 3 Cu 2: Cho mch gm in tr thun R, t in C v cun dy thun cm L mc ni tip. Khi ch ni R,C vo ngun in xoay chiu th thy dng in i sm pha /4 so vi in p t vo mch. Khi mc c R, L, C vo mch th thy dng in i chm pha /4 so vi in p hai u on mch. Mi lin h no sau y l ng: A. ZC = 2ZL; B. R = ZL = ZC; C. ZL= 2ZC; D. ZL = ZC. Cu 3: Cho mch gm in tr R v cun dy thun cm L mc ni tip, L thay i c. in p hiu dng hai u mch l U, tn s gc = 200(rad/s). Khi L = L1 = /4(H) th u lch pha so vi i gc 1 v khi L = L2 = 1/ (H) th u lch pha so vi i gc 2 . Bit 1 + 2 = 900. Gi tr ca in tr R l A. 50 . B. 65 . C. 80 . D. 100 . Cu 4 : Mt cun dy mc vo ngun xoay chiu u = 200cos(100 t- /2) (V), th cng dng in qua cun dy 5 l: i = 2 cos (100 t ). H s t cm ca cun dy l: 6 1 2 2 6 A. L = H B. L = H C. L = H D. L = H 2 C N B

A

L M

R

Cu 5: Cho mch in xoay chiu nh hnh v. Bit ZL = 20 ; ZC = 125 . t vo hai u mch in mt in p xoay chiu u = 200 2 cos 100t (V). iu chnh R uAN v uMB vung pha, khi in tr c gi tr bng: A. 100 . B. 200 . C. 50 . D. 130 . Cu 6: mch in R=100 ; C = 10-4/(2 )(F). Khi t vo AB mt in p xoay chiu c tn s f = 50Hz th uAB v uAM vung pha vi nhau. Gi tr L l: A. L = 2/ (H) B. L = 3/ (H) C. L = 3 / (H) D. L = 1/ (H) Cu 7: Cho bit: R = 40 , C =2,5

10 4 F v:

u AM = 80 cos100 t (V ) ; uMB = 200 2 cos(100t +r v L c gi tr l: A. r = 100 , L =3 10 3 H B. r =10 L = , H

7 ) (V ) 12

R A

C M

L, r B

1 C. r = 50 , L = H 2

D.

r = 50 , L =

2

H

1,5 103 H ; f = 50 Hz khi C= F v 5 103 C= F th dng in qua mch lch pha nhau . in tr R bng: 2,5 3 Cu 8: mch in xoay chiu L = A. 50 B. 100 3 C. 100 D. p n khc. Cu 9: Chn cu ng. Mt on mch gm cun dy c cm khng 20 v t in c in dung C = ni tip. Cng dng in qua mch c biu thc i = 2cos 100t + th ta mc thm in tr R c gi tr l: A. 25 B. 20 5

(

4

) (A)

4.10-4 F mc

. tng tr ca mch l Z = ZL+ZC D. 20

C. 0

Cu 10 : Cho on mch nh hnh v . R = 100 , cun dy c L = 318mH v C R L A in tr thun khng ng k, t in c in dung C = 15,9 F . in p hai u B M N on mch AB l u = U 2 cos100 t(V). lch pha gia uAN v uAB l A. 300. B. 600. C. 900. D. 1200. Cu 11 . Khi t in p khng i 12 V vo hai u mt cun dy c in tr thun R v t cm L th dng in qua cun dy l dng in mt chiu c cng 0,15 A. Nu t vo hai u cun dy ny mt in p xoay chiu c gi tr hiu dng 100 V th cng dng in hiu dng qua n l 1 A. Cm khng ca cun dy l A. 50 . B. 30 . C. 40 . D. 60 . 10 4 Cu 12: Mch in xoay chiu gm mt t in c in dung C = ( F ) mc ni tip vi cun dy c in tr1 ( H ) . t vo hai u on mch mt in p xoay chiu u = 5 2 co 2 0 s ft thun R = 25 v t cm L = 4 (V) th dng in trong mch c cng hiu dng I = 2 (A). Tn s ca dng in trong mch l A. 50Hz B. 50 2 Hz C. 100 Hz D. 200Hz Cu 13: Mt on mch xoay chiu nh hnh v. u = 100 2 cos 100t(V). Khi thay i in dung C, ngi ta thy c hai gi tr ca C l 5F v 7F th Ampe k u ch 0,8A. H s t cm L ca cun dy v in tr R l: A. R = 75,85; L =1,24H B. R = 80,5; L = 1,5H A R L , r C C. R = 95,75; L = 2,74H D. Mt cp gi tr khc A Cu 14: Mt on mch RLC ni tip, L=1/(H), in p hai u on mch l u = 100 2cos100 t(V) . Mch tiu th cng sut 100W. Nu mc vo hai u L mt ampe k nhit c in tr khng ng k th cng sut tiu th ca mch khng i. Gi tr ca R v C l:

B

A. 100,

2.10 4 (F)

B. 50,

2.10 4 (F)

C. 100,

10 4 (F)

D. 50,

10 4 (F)

TM PHN T X TRONG MCH RLCCu 1: Cho mt on mch xoay chiu gm hai trong ba phn t R, L, C mc ni tip. in p gia hai u on mch v cng dng in trong mch c biu thc: u = 200 2 cos(100 t )(V ); i = 5sin(100 t / 3)( A) . p n no sau y l ng? A. on mch c hai phn t R-C, c tng tr 40 2 ; B. on mch c hai phn t L-C, c tng tr 40 ; C. on mch c hai phn t R-L, c tng tr 40 2 ; D. on mch c hai phn t R-C, c tng tr 40 . Cu 2: t vo hi u on mch AB mt in p u = 100 2 cos(100 t)(V), t in c in dung C = 10-4/ (F). Hp X ch cha mt phn t(in tr hoc cun dy thun cm) i sm pha hn u AB mt gc /3. Hp X cha in tr hay cun dy? Gi tr in tr hoc t cm tng ng l bao nhiu? A. Hp X cha in tr: R = 100 3 . B. Hp X cha in tr: R = 100/ 3 . C. Hp X cha cun dy: L =

3 / (H).

D. Hp X cha cun dy: L =

3 /2 (H). A

C

X

B

Cu 3: Cho nhiu hp kn ging nhau, trong mi hp cha mt trong ba phn t R0, L0 hoc C0. Ly mt hp bt k mc ni tip vi mt in tr thun R = 20 . t vo hai u on mch in p xoay chiu c biu thc dng u = 200 2 cos 100t (V) th dng in trong mch c biu thc i = 2 2 sin(100t + / 2)(A) . Phn t trong hp kn l F A. L0 = 318mH . B. R0 = 80 . C. C0 = 100 / . D. R0 = 100 . Cu 4: Cho hp kn gm 2 trong 3 phn t R0, L0 hoc C0 mc ni tip. Mc hp kn ni tip vi t in c in dung C

103 F . t vo hai u on mch in p xoay chiu c biu thc u = 120 2 cos(100t + / 4)(V) th dng 3 2 in trong mch l i = 2 2 cos 100t ( A) . Cc phn t trong hp kn l:= A. R0 = 60 2 , L0 = 6 2 / 3 H. B. R0 = 30 2 , L0 = 2 / 3 H. C. R0 = 30 2 , L0 = 6 2 / 2 H. D. R0 = 30 2 , L0 = 6 2 / 3 H. Cu 5: Cho on mch nh hnh v. Hp en X cha mt trong ba phn t R0, L0 hoc C0; R l bin tr. t vo hai u mch in mt in p xoay chiu c dng u = 200 2 cos 100t (V). iu chnh R Pmax khi cng dng in cc i trong mch l 2 A, bit cng dng in trong mch sm pha so vi in p hai u mch. Xc nh phn t trong hp X v tnh gi tr ca phn t ?

Cu 6: Cho mch in xoay chiu nh hnh v. Bit cun dy thun cm L = 636mH, t in c in dung C = 31,8 F , hp en X cha 2 trong 3 phn t R0, L0 hoc C0 mc ni tip. t vo hai u on mch in p xoay chiu c biu thc u = 200 cos 100t (V) . Bit cng dng in hiu dng trong mch l 2,8A, h s cng sut ca mch cos = 1 . Cc phn t trong X l A. R0 = 50 ; C0 = 318 F . B. R0 = 50 ; C0 = 31,8 F .C. R0 = 50 ; L0 = 318mH. D. R0 = 100 ; C0 = 318 F . C Cu 7: Mch in nh hnh v, uAB = U 2 cos t ( V). N R X A B Khi kha K ng : UR = 200V; UC = 150V Khi kha K ngt : UAN = 150V; UNB = 200V. Xc nh cc phn t trong hp X ? K A. R0L0. B. R0Co. C. L0C0. D. R0. Cu 8 : Cho mt hp kn X ch cha 1 phn t l R,L, C, mc hp kn trn vo mch in xoay chiu c U = const khi dng in trong mch c mt gi tr no . Mc thm mt phn t khc vo mch th thy dng in trong mch t gi tr cc i l v cng. Cc phn t trong X v mc thm l g? A. R v L B. L v C C. R v R D. R v C . Cu 9: mch in hp kn X gm mt trong ba phn t n tr thun, cun dy, t in. Khi t vo AB in p xuay chiu c UAB=250V th UAM=150V v UMB=200V. Hp kn X l A. cun dy cm thun. B. cun dy c in tr khc khng. C. t in. D. in tr thu

1 A. Cun cm, L0 = (H).

10 4 B. T in, C0 = (F) .

A C A

X

L

R X

B

B

Cu 10 : mch in hp kn X l mt trong ba phn t in tr thun, cun dy, t in. Khi t vo AB mt in p xoay chiu c tr hiu dng 220V th in p hiu dng trn on AM v MB ln lt l 100V v 120V . Hp kn X l: A. in tr. B. Cun dy thun cm. C. T in. D. Cun dy c in tr thun. Cu 11: Mch in xoay chiu A,B gm cun dy cm thun mc ni tip vi hp kn X. Bit rng hp kn cha 2 trong 3 phn t R 0, L0, C0 mc ni tip. in p hai u mch A,B chm pha cng dng in trong mch. Cc phn t trong hp kn X gm: A. L0 v C0 sao cho Z L0 = ZC0 B. R0 v C0 C. L0 v C0 D. R0 v L0.

rad so vi 6

Cu 12 : Cho cun dy c r = 50 ; ZL= 50 3 mc ni tip vi mch in X gm hai trong ba phn t R,L,C. t vo hai u on mch in p xoay chiu. Sau khi in p trn cun dy t cc i mt phn t chu k th hiu in trn X t cc i.Trong X cha cc phn t tho mn: A). Gm C v L tho mn: ZC- ZL= 50 3 C). Gm C v R tho mn:

R = 3 ZC

R =2 ZC R = 3 D). Gm R v L tho mn: ZLB). Gm C v R tho mn:

Cu 13: Cho on mch AB nh hnh v trn . X v Y l hai hp, mi hp ch cha hai trong ba phn t: in tr thun, V V cun dy thun cm v t in mc ni tip. Cc vn k V1, V2 v ampe k o c c dng in xoay chiu v mt chiu. in tr cc vn k rt ln, in tr 1 2 A ampe k khng ng k. Khi mc hai im A v M vo hai cc ca ngun in A B X M Y mt chiu, ampe k ch gi tr I, V1 ch U. Nh v A. Hp X gm t v in tr. B. Hp X gm t v cun dy. C. Hp X gm cun dy v in tr. D. Hp X gm hai in tr. Cu 14: Tng t u cu 11. Sau mc A v B vo ngun xoay chiu hnh sin, tn s f th thy u AM v uMB lch pha nhau /2. Nh vy A. Hp Y gm t v in tr. B. Hp Y gm t in v cun dy. C. Hp Y gm cun dy v in tr D. Hp Y gm hai t in. Cu 15: Ba linh kin t in, in tr, cun dy c t ring bit trong ba hp kn c nh s bn ngoi mt cch ngu nhin bng cc s 1, 2, 3. Tng tr ca mi hp i vi mt dng in xoay chiu c tn s xc nh u bng 1k . Tng tr ca hp 1, 2 mc ni tip i vi dng in xoay chiu l Z 12 = 2 k . Tng tr ca hp 2, 3 mc ni tip i vi dng in xoay chiu l Z23 = 0,5k . Tng hp 1,2,3 l g ? A. Hp 1 l t in, hp 2 l in tr, hp 3 l cun dy. B. Hp 1 l in tr, hp 2 l t in, hp 3 l cun dy. C. Hp 1 l t in, hp 2 l cun dy, hp 3 l t in. D. Hp 1 l in tr, hp 2 l cun dy, hp 3 l t in.

IN P TRONG MCH RLCCu 16(H - 2010): t in p u = U0cos t vo hai u on mch gm in tr thun R, cun cm thun c t cm L v t in c in dung C mc ni tip. Gi i l cng dng in tc thi trong on mch; u 1, u2 v u3 ln lt l in p tc thi gia hai u in tr, gia hai u cun cm v gia hai u t in. H thc ng l A.

i=

u 1 2. R + ( L ) C2

B. i = u3C.

C. i =

u1 . R

D. i =

u2 . L

Cu 17(C- 2008): Mt on mch gm cun dy thun cm (cm thun) mc ni tip vi in tr thun. Nu t in p u = 152sin100t (V) vo hai u on mch th in p hiu dng gia hai u cun dy l 5 V. Khi , in p hiu dng gia hai u in tr bng A. 52 V. B. 5 3 V. C. 10 2 V. D. 103 V. Cu 18 : Cho mch in xoay chiu RLC mc ni tip. Cun dy thun cm khng. in p hiu dng gia hai u on mch A v B l U = 200V, UL = 8UR/3 = 2UC. in p gia hai u in tr R l A. 100V. B. 120V. C. 150V. D. 180V. Cu 19: t in p xoay chiu u = U 2cos(t )V vo hai u on mch RLC khng phn nhnh c quan h gia cc in p hiu dng l U=2UL=UC th A. dng in tr pha hn in p hai u mch. B. dng in tr pha hn in p hai u mch. 3 6

hn in p hai u mch. D. dng in sm pha hn in p hai u mch 6 3 Cu 20: Cho mt on mch xoay chiu ni tip gm in tr R, cun dy thun cm L v t C. t vo hai u on mch in p u = 100 2co s(100p t )V , lc Z L = 2 Z C v in p hiu dng hai u in tr l U R = 60V . in p hiu dng hai u cun dy l: A.160V B.80V C.60V D. 120V Cu 21: Mt mch in gm cc phn t in tr thun R, cun thun cm L v t in C mc ni tip. t vo mch in mt in p xoay chiu n nh. in p hiu dng trn mi phn t u bng nhau v bng200V. Nu lm ngn mch t in (ni tt hai bn cc ca n) th in p hiu dng trn in tr thun R s bng A.100 V. B. 200 V. C. 200 V. D. 100 V. Cu 22. Mch in xoay chiu gm in tr thun R =30( )mc ni tip vi cun dy.t vo hai u mch mt in p xoay chiu u = U sin(100 t)(V).in p hiu dng hai u cun dy l Ud = 60 V. Dng in trong mch lch pha /6 so vi u v lch pha /3 so vi ud. in p hiu dng hai u mch ( U ) c gi tr A. 60 (V). B. 120 (V). C. 90 (V). D. 60 (V). Cu 23: on mch in xoay chiu RLC ni tip. in p hiu dng hai u on mch l U = 123V, UR = 27V; UL = 1881V. Bit rng mch c tnh dung khng. in p hiu dng hai u t in l A. 200V. B. 402V. C. 2001V. D. 201V. Cu 24: on mch in xoay chiu RLC, trong R l bin tr. in p hai u mch c gi tr hiu dng khng i v tn s khng i. Khi UR=10 3 V th UL=40V, UC=30V. Nu iu chnh bin tr cho UR=10V th UL v UC c gi tr A. 69,2V v 51,9V B. 58,7V v 34,6V C. 78,3V v 32,4V D. 45,8V v 67,1V Cu Chn cu ng. Cho mach in xoay chiu nh hnh v cun dy R L C thun cm. Ngi ta o c cc in p UAN = UAB = 20V; UMB 25 : A M N B = 12V. in p UAM, UMN, UNB ln lt l:C. dng in sm phaHnh 3.2

A. UAM = 12V; UMN = 32V; UNB =16V B. UAM = 16V; UMN = 12V; UNB =24V C. UAM = 16V; UMN = 24V; UNB =12V D. UAM = 12V; UMN = 16V; UNB =32V Cu 26: :t vo hai u mch in xoay chiu gm mt cun dy v mt t in mc ni tip mt in p xoay chiu n nh c biu thc u = 100 6 cos(100 t +

)(V ). Dng vn k c in tr rt ln ln lt o in p gia hai 4

u cun cm v hai bn t in th thy chng c gi tr ln lt l 100V v 200V. Biu thc in p gia hai u cun dy l:

)(V ) B. ud = 200 cos(100 t + )(V ) . 2 4 3 3 )(V ) . D. ud = 100 2 cos(100 t + )(V ) . C. ud = 200 2 cos(100 t + 4 4A. ud = 100 2 cos(100 t +

Cu 27: Cho on mch RLC ni tip. t vo hai u mch in in p u = 100 6 cos t(V). Bit uRL sm pha hn dng in qua mch gc /6(rad), uC v u lch pha nhau /6(rad). in p hiu dng gia hai bn t l A. 200V. B. 100V. C. 100 3 V. D. 200/ 3 V. Cu 28(H 2008): Cho on mch in xoay chiu gm cun dy mc ni tip vi t in. lch pha ca in p gia hai u cun dy so vi cng dng in trong mch l

. in p hiu dng gia hai u t in bng 3

3 ln

in p hiu dng gia hai u cun dy. lch pha ca in p gia hai u cun dy so vi in p gia hai u on mch trn l A. 0. B.

2 . D. . 3 3 Cu 29(CAO NG 2010): t in p u = 220 2 cos100 t (V) vo hai u on mch AB gm hai on mch AMC. v MB mc ni tip. on AM gm in tr thun R mc ni tip vi cun cm thun L, on MB ch c t in C. Bit in p gia hai u on mch AM v in p gia hai u on mch MB c gi tr hiu dng bng nhau nhng lch pha nhau

. 2

2 . in p hiu dng gia hai u on mch AM bng 3

A. 220 2 V.

B.

220 V. 3

C. 220 V.

D. 110 V.

Cu 30: on mch xoay chiu nh hnh v. RV , vn k (V1) ch 80(V), vn k (V2) ch 100(V) v vn k (V) ch 60(V). lch pha uAM vi uAB l: V A. 37 B. 53 C. 90 D. 45 C LA M B

Cu 31: Cho mch RLC ni tip. R = 100 ; cun dy thun cm L = 1/2 (H), t V1 V2 C bin i. t vo hai u on mch in p u = 120 2 sin(100 t)(V). Xc nh C UC = 120V. A. 100/3 ( F). B. 100/2,5 ( F). C. 200/ ( F). D. 80/ ( F). Cu 32: Cho mch RLC ni tip. Trong R v L xc nh. Mch c t di in p u = U 2 sin t(V). Vi U khng i, cho trc. Khi in p hiu dng gia hai u t in cc i. Gi tr ca C xc nh bng biu thc no sau? A. C =

L L . B. C = 2 . 2 R + L R + 2 L22

C. C =

L . R + L2

D. C =

L . R + 2 L

Cu 33: Cho mch mc theo th t RLC mc ni tip, t v hai u on mch in p xoay chiu ,bit R v L khng i cho C thay i .Khi UC t gi tr cc i th h thc no sau y l ng A. U2Cmax= U2 + U2(RL) B. UCmax = UR + UL C. UCmax = UL 2 D. UCmax = 3 UR. Cu 34: Mt on mch AB gm hai on mch AM v MB mc ni tip. on mch AM c in tr thun 50 mc 1 ( H ) on mch MB ch c t in vi in dung thay i c. t in p ni tip vi cun cm thun c t cmu = U 0 cos 100 t (V) vo hai u on mch AB. iu chnh in dung ca t in n gi tr C1 sao cho in p hai u on mch AB lch pha /2 so vi in p hai u on mch AM. Gi tr ca C1 bng 4.10 5 8.10 5 2.10 5

A.

10 5

(F).

B.

(F)

C.

(F)

D.

(F)

Cu 135:t in p xoay chiu u = U 2cos(t )V vo hai u on mch RLC khng phn nhnh. Khi thay i in dung C thy in p hiu dng UC gim. gi tr UC lc cha thay i C c th tnh theo biu thc l:2 2 2 2 2 2 U UR +UL U UR +UL U R2 + Z L U R2 + Z L B. U C = C. U C = D. U C = 2U R UR ZL 2Z L -4 Cu 36: Cho mch in xoay chiu RLC mc ni tip. Trong R = 100, L = 1/(H), C = 2.10 /(F) on mch c mc vo in p xoay chiu c tn s f = 50(Hz). Mc thm C vi C th thy in p trn b t in t gi tr cc i. Gi tr v cch mc C l: A. C = 10-4/15 (F) mc ni tip vi C. B. C = 10-4/15 (F) mc song song vi C. C. C = 10-3/15 (F) mc ni tip vi C. D. C = 10-3/15 (F) mc song song vi

A. U C =

Cu 37 : Cho mch in gm cun dy v t in mc ni tip. Cun dy c in tr hot ng R = 100 ; t cm L = 3 / (H). in p uAB = 100 2 sin100 t(V). Vi gi tr no ca C th in p gia hai u t cc i v tnh gi tr cc i ? Hy chn kt qu ng.3 3 .10 4 F; UCmax = 220V. B. C = .10 6 F; UCmax = 180V. 4 3 4 3 C. C = .10 4 F; UCmax = 200V. D. C = .10 4 F; UCmax = 120V. 4

A. C =

Cu 38: Mt mch in gm in tr thun R, cun dy thun cm v mt t in c in dung thay i c mc ni tip. t vo hai u on mch trn mt in p xoay chiu c biu thc u = U 0 cos t (V). Khi thay i in dung ca t cho in p gia hai bn t t cc i v bng 2U. Ta c quan h gia ZL v R l:

A.

ZL =

Cu 39: Cho mch in xoay chiu RLC mc ni tip, bit L = 2 / 25(H ) , R = 6 , in p hai u on mch c dng u = U 2 cos 100t (V) . iu chnh in dung C in p hiu dng trn t in t gi tr cc i l 200V. in p hiu dng gia hai u on mch bng: A. 100V. B. 200V. C. 120V. D. 220V. Cu 40: Cho mch in xoay chiu RLC mc ni tip, bit L = 2 / 25(H ) , R = 6 , in p hai u on mch c dng

R . 3

B.

ZL = 2R.

C.

ZL =

3 R.

D.

ZL = 3R.

u = 80 2 cos100t (V) . iu chnh in dung C in p hiu dng trn t in t gi tr cc i l 100V. in phiu dng gia hai u on mch RL bng: A. 100V. B. 200V. C. 60V. D. 120V.

Cu 41(C- 2008): Mt on mch RLC khng phn nhnh gm in tr thun 100 , cun dy thun cm c h s t cm L=1/(10) v t in c in dung C thay i c. t vo hai u on mch in in p u = 200 2sin100 t (V). Thay i in dung C ca t in cho n khi in p gia hai u cun dy t gi tr cc i. Gi tr cc i bng A. 200 V. B. 1002 V. C. 502 V. D. 50 V Cu 42 : in p 2 u AB: u = 120sin t (V). R = 100 ; cun dy thun cm c t cm L thay i v; t C c dung khng 50 . iu chnh L ULmax, gi tr ULmax l A. 65V. B. 80V. C. 92V. 130V. Cu 43: Mt mch in gm RLC mc ni tip. Trong , R = 40, L = 1/5 (H), C l mt t in c in dung thay i c vi gi tr ban u C = 10-3/5 (F). Mch c mc vo mng in xoay chiu c tn s f = 50(Hz) v in p hiu dng U = 200(V). iu chnh t in C gim v 0. Khi in p trn hai bn t in s: A. tng dn. B. gim dn. C. ban u gim sau tng dn. D. ban u tng sau gim dn. Cu 44. Mch in xoay chiu gm 3 phn t R, L, C mc ni tip nh hnh v. in L C R tr R v t in C c gi tr khng i, cun dy thun cm c t cm L c th thay M N B i gi tr. t vo hai u A, B ca mch in mt in p xoay chiu c tn s f, in A p hiu dng U n nh, iu chnh L c uMB vung pha vi uAB. Tip tng gi tr ca L th trong mch s c: A. UAM tng, I gim. B. UAM gim, I tng. C. UAM tng, I tng. D. UAM gim, I gim. Cu 45: Cho mch in xoay chiu RLC ni tip . Cho R = 100 ; C = 100/ ( F). Cun dy thun cm c t cm L thay i c. t vo hai u on mch mt in p uAB = 200sin100 t(V). Gi tr L UL t cc i l A. 1/ (H). B. 1/2 (H). C. 2/ (H). D. 3/ (H). Cu 46: Cho mch RLC mc ni tip, bit R = 100 3 ; C = 50 / (F) ; t cm L thay i c. t vo hai u on mch in p xoay chiu n nh u = 200. cos 100t (V ) . in p hiu dng gia hai u cun cm cc i th cm khng bng: A. 200 . B. 300 . C. 350 . D. 100 . Cu 47 : Mt mch in xoay chiu mc ni tip gm mt in tr, mt t in v mt cun dy thun cm c h s t cm L c th thay i, vi u l in p hai u on mch v uRC l in p hai u on mch cha RC, thay i L in p hai u cun dy t gi tr cc i khi kt lun no sau y l sai A. u v uRC vung pha. B. (UL) Max= U + U2

2

2 RC

2 ZC + R2 C. Z L = ZC

D. (U L ) Max

Cu 48 : Cho mch RLC ni tip. Trong R v C xc nh. Mch c t di in p u = U 2 sin t(V). Vi U khng i, cho trc. Khi in p hiu dng gia hai u cun cm cc i. Gi tr ca L xc nh bng biu thc no sau?A. L = 2CR2 + 1/(C 2 ). B. L = R2 + 1/(C2 2 ). C. L = CR2 + 1/(C 2 ). D. L = CR2 + 1/(2C 2 ). Cu 49: Cho mch in xoay chiu RLC mc ni tip, c t cm L thay i c, t vo hai u on mch in p xoay chiu n nh. iu chnh L ULmax khi L A. in p hai u on mch sm pha so vi uMB mt gc / 4 . C R A B B. in p hai u on mch sm pha so vi uMB mt gc / 2 . M C. in p hai u on mch tr pha so vi uMB mt gc / 4 . D. in p hai u on mch tr pha so vi uMB mt gc / 2 .

2 U R 2 + ZC = ZC

Cu 50 : Cho mch in xoay chiu RLC mc ni tip, bit R = 30 , r = 10 , L = 0,5 / (H), t c in dung C bin i. t gia hai u on mch in p

xoay chiu c dng u = 100 2 . cos 100t (V ) . iu chnh C in p U MB t gi tr cc tiu khi dung khng ZC bng: A. 50 . B. 30 . C. 40 . D. 100 . Cu 51.Cho mch in xoay chiu c t in C=

A

RM

L,r

C

B

1 -4 .10 F , in tr R, v cun dy thun cm c L thay i c. in 5 p xoay chiu t vo hai u on mch c gi tr hiu dng l 100V, tn s 50Hz. Khi L= H th in p hiu dng 4trn cun dy cc i. Hi khi L thay i cng sut cc i l bao nhiu? A). 100W B). 200W C). 400W D). 50W

Cu 52(H 2009): t mt in p xoay chiu c gi tr hiu dng U vo hai u on mch AB gm cun cm thun c t cm L, in tr thun R v t in c in dung C mc ni tip theo th t trn. Gi U L, UR v UC_ln lt l cc in p hiu dng gia hai u mi phn t. Bit in p gia hai u on mch AB lch pha

so vi in p gia hai 2

u on mch NB (on mch NB gm R v C ). H thc no di y l ng? 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 A. U = U R + U C + U L . B. U C = U R + U L + U . C. U L = U R + U C + U D. U R = U C + U L + U Cu 53: Cho mch in RLC mc ni tip, cc i lng R, L v C khng i. t vo hai u on mch in p xoay chiu c biu thc u = 200 6 cos t (V), tn s dng in thay i c. iu chnh tn s in p hiu dng trn in tr cc i, gi tr cc i bng: A. 200V. B. 200 6 (V). C. 200 3 (V). D. 100 6 (V). 7: t vo hai u mch in RLC mt in p xoay chiu c gi tr hiu dng khng i th in p hiu dng trn cc phn t R, L v C ln lt bng 60V, 100V v 20V. Khi thay t C bng t C 1 trong mch c cng hng in th in p hiu dng hai u in tr bng A. 120 2 V C. 100V B. 60V D. 100 2 V Cu 54: t in p u = U0cos100t n nh vo hai u on mch RLC khng phn nhnh. Bit L = (H) thun cm , C=

A. lun gim khi R thay i. B. khng i khi R thay i C. gim 2 ln nu R gim hai ln . D. gim 2 ln nu R tng hai ln] Cu 55(H - 2010): t in p xoay chiu c gi tr hiu dng 200 V v tn s khng i vo hai u A v B ca on mch mc ni tip theo th t gm bin tr R, cun cm thun c t cm L v t in c in dung C thay i. Gi N l im ni gia cun cm thun v t in. Cc gi tr R, L, C hu hn v khc khng. Vi C = C 1 th in p hiu dng gia hai u bin tr R c gi tr khng i v khc khng khi thay i gi tr R ca bin tr. Vi C = dng gia A v N bng A. 200 V.

10 4 (F), R bin tr (R 0) . Mc vo hai u bin tr mt vn k nhit, ri thay i R . S ch vn k s

C1 th in p hiu 2

B. 100 2 V. C. 100 V. D. 200 2 V. Cu 56 : Cho mch in xoay chiu RLC mc ni tip, bit R = 100 3 ; in p xoay chiu gia hai u on mch c dng u = U 2 . cos 100t (V ) , mch c L bin i c. Khi L = 2 / (H) th ULC = U/2 v mch c tnh dung khng. ULC = 0 th t cm c gi tr bng

2 (H). Cu 57 : Mt on mch in xoay chiu RLC mc ni tip, gm in tr thun R = 100 , cun cm c t cm L = 1 / (H) v t in c in dung C = 100 / ( F ). t vo hai u on mch in p xoay chiu n nh c biu thc u = 100 3 cos t, tn s dng in thay i c. iu chnh tn s in p hiu dng trn t in t cc i, gi trA. B. C. D. cc i bng: A. 100V. B. 50V. C. 100 2 V. D. 150V.

3 (H).

1 (H). 2

1 (H). 3

Cu 58 : Mt on mch in xoay chiu RLC mc ni tip, gm in tr thun R = 100 , cun cm c t cm L = 1 / (H) v t in c in dung C = 100 / ( F ). t vo hai u on mch in p xoay chiu n nh c biu thc u

= 100 3 cos t, tn s dng in thay i c. in p hiu dng gia hai u t in t gi tr cc i th tn s gc ca dng in bng: A. 100 (rad/s). B. 100 3 (rad/s). C. 200 2 (rad/s). D. 100 / 2 (rad/s). H, C = 100/ F. t vo hai u on mch in p Cu 59 : Cho mch in RLC mc ni tip, c R = 100 , L = 1/ xoay chiu c biu thc u = 100 3 cos( t), c tn s f bin i. iu chnh tn s in p trn cun thun cm cc i, in p cc i trn cun cm c gi tr l: A. 100V. B. 100 2 V. C. 100 3 V. D. 200V. Cu 60: Cho mch in xoay chiu RLC mc ni tip gm R = 50 , cun dy thun cm c t cm L = / 10 (H) v t in c in dung C = 100 / (F) . t vo hai u on mch in p xoay chiu n nh c biu thc u = U 2 cos t, tn s dng in thay i c. in p hiu dng gia hai u cun cm t gi tr cc i khi tn s dng in xoay chiu bng: A. 58,3Hz. B. 85Hz. C. 50Hz. D. 53,8Hz Cu 61: Mt mch in xoay chiu gm cc linh kin l tng R, L, C mc ni tip. Tn s (gc) ring ca mch l 0, in tr R c th thay i. Hi cn phi t vo mch mt in p xoay chiu c gi tr hiu dng khng i, c tn s (gc) bng bao nhiu in p URL khng ph thuc vo R? 0 A. = 0 B. = 0 2 C. =2 0 D. = 2 Cu Cho mt on mch c cun dy thun cm (HV) c t vo hai u mch mt in p xoay chiu c 62: in p hiu dng khng i, khi iu chnh t in c hin tng cng hng xy ra th ZC = 100 . Tip tc thay i in dung C in p hiu dng gia hai im AM khng ph thuc vo in tr R th ZC l A. ZC = 150

B. ZC = 50

C. ZC = 200

D. ZC = 100

Cu 63: t in p u = U 2 cos t vo hai u on mch AB gm hai on mch AN v NB mc ni tip. on AN gm bin tr R mc ni tip vi cun cm thun c t cm L, on NB ch c t in vi in dung C. t 1 1 = in p hiu dng gia hai u on mch AN khng ph thuc R th tn s gc bng 2 LC A.

2 1

B. 2 1

C.

12

D.

1

2 2

Ph lc12. on mch RLC c L thay i:

1 th IMax URmax; PMax cn ULCMin Lu : L v C mc lin tip nhau 2C 2 2 R 2 + ZC U R 2 + ZC 2 2 2 2 2 2 * Khi Z L = th U LMax = v U LMax = U + U R + UC ; U LMax UC ULMax U = 0 ZC R* Khi L =

* Vi L = L1 hoc L = L2 th UL c cng gi tr th ULmax khi * Khi Z L = * Khi C =

1 1 1 1 2 L1 L2 = ( + ) L= Z L 2 Z L1 Z L2 L1 + L2

2 2UR Z C + 4 R 2 + ZC th U RLMax = Lu : R v L mc lin tip nhau 2 4 R 2 + Z C ZC 2

13. on mch RLC c C thay i:

1 th IMax URmax; PMax cn ULCMin Lu : L v C mc lin tip nhau 2L 2 2 R2 + ZL U R2 + ZL 2 2 2 2 2 2 * Khi Z C = th U CMax = v U CMax = U + U R + U L ; UCMax U L UCMax U = 0 ZL R 1 1 1 1 C + C2 = ( + )C = 1 * Khi C = C1 hoc C = C2 th UC c cng gi tr th UCmax khi Z C 2 ZC1 ZC2 2* Khi Z C =2 2UR Z L + 4R2 + ZL th U RCMax = Lu : R v C mc lin tip nhau 2 2 4R + Z L ZL 2

14. Mch RLC c thay i: * Khi =

1 th IMax URmax; PMax cn ULCMin Lu : L v C mc lin tip nhau LC 1 1 = 2U .L 2U .L 1 L R2 C L R 2 th U LMax = * Khi * Khi = th U CMax = 2 2 R 4 LC R C R 4 LC R 2C 2 L C 2 C 2* Vi = 1 hoc = 2 th I hoc P hoc UR c cng mt gi tr th IMax hoc PMax hoc URMax khi

= 12 tn s f =

f1 f 2

CNG SUT CA DNG IN XOAY CHIUBI TON THUN Cu 1: Chn cu ng. Cho on mch RLC nh hnh v (Hnh 3.5). R=100 , cun dy thun cm c t cm L =

2 H v t in c in dung

R A M

L NHNH 3.5

C B

C= u AN

10

4

= 200cos100t (V) . Cng sut tiu th ca dng in trong on mch l:

F . Biu thc in p tc thi gia hai im A v N l:

A.100W B.40W C.50W D.60W Cu 2: Mt dng in xoay chiu c biu thc i = 5cos100 t(A) chy qua in tr thun bng 10 . Cng sut to nhit trn in tr l A. 125W. B. 160W. C. 250W. D. 500W. Cu 3(H 2008): t vo hai u on mch in RLC khng phn nhnh mt in p u = 220 2 cos t th cng dng in qua on mch c biu thc l i = 2 2 cos t l A. 440W. B. 220 2 W. C. 440 2 W. D. 220W

(V) 2

(A). Cng sut tiu th ca on mch ny 4

Cu 4: Cho mch in xoay chiu RLC mc ni tip, cho R = 50 . c vo hai u on mch in p u = 100 2 cos t (V) , bit in p gia hai bn t v in p gia hai u on mch lch pha nhau mt gc l /6. Cng sut tiu th ca mch in l A. 100W. B. 100 3 W. C. 50W. D. 50 3 W Cu 5: Cho mch in c 2 phn t mc ni tip l t C v in tr R. lch pha gia uAB v dng in i ca mch ng vi cc gi tr R1 v R2 ca R l l 1 v 2. Bit 1 + 2 = /2. Cho R1 = 270 ; R2 = 480 , UAB = 150 V. Gi P1 v P2 l cng sut ca mch ng vi R1 v R2.Tnh P1 v P2 A. P1 = 30 W; P2 = 30 W. B. P1 = 50 W; P2 = 40 W. C. P1 = 40 W; P2 = 40 W. D. P1 = 40 W; P2 = 50 W.

BI TON NGCCu 6: Mt ngun xoay chiu c gi tr cc i ca in pl 340V. Khi ni mt in tr vi ngun in ny, cng sut to nhit l 1kW. Nu ni in tr vi ngun in khng i 340V th cng sut to nhit trn in tr l A. 1000W. B. 1400W. C. 2000W. D. 2800W. Cu 7: Cho mch in xoay chiu RLC ni tip, R bin i. Bit L = 1/ H; C = 10-3/4 F. t vo hai u on mch mt in p xoay chiu uAB = 75 2 cos100 t(V). Cng sut trn ton mch l P = 45W. in tr R c gi tr bng bao nhiu? A. 45 . B. 60 . C. 80 . D. 45 hoc 80 . Cu 8: Cho mch in RLC ni tip. Cho R = 100 ; C = 100/ ( F); cun dy thun cm c t cm L thay i c. t vo hai u on mch mt in p u = 200cos100 t(V). t cm L bng bao nhiu th cng sut tiu th trong mch l 100W. A. L = 1/ (H).B. L = 1/2 (H). C. L = 2/ (H). D. L = 4/ (H). Cu 9(H 2009): t in p xoay chiu c gi tr hiu dng khng i vo hai u on mch gm bin tr R mc ni tip vi t in. Dung khng ca t in l 100 . Khi iu chnh R th ti hai gi tr R1 v R2 cng sut tiu th ca on mch nh nhau. Bit in p hiu dng gia hai u t in khi R = R1 bng hai ln in p hiu dng gia hai u t in khi R = R2. Cc gi tr R1 v R2 l: A. R1 = 50 , R2 = 100 . B. R1 = 40 , R2 = 250 . C. R1 = 50 , R2 = 200 . D. R1 = 25 , R2 = 100 Cu 10: Cho on mch in xoay chiu RC mc ni tip. R l bin tr, t c in dung C = 100/ ( F). t vo hai u mch in mt in p xoay chiu n nh u, tn s f = 50Hz. Thay i R ta thy ng vi hai gi tr ca R = R1 v R = R2 th cng sut ca mch u bng nhau. Khi R1.R2 l A. 104. B. 103. C. 102. D. 10. Cu 11(CAO NG 2010): t in p u = U 2 cos t (V) vo hai u on mch gm cun cm thun mc ni tip vi mt bin tr R. ng vi hai gi tr R1 = 20 v R2 = 80 ca bin tr th cng sut tiu th trong on mch u bng 400 W. Gi tr ca U l A. 400 V. B. 200 V. C. 100 V. D. 100 2 V. Cu 12 : Cho on mch mc ni tip trong t din c in dung thay i c bit in p hai u on mch l u=200 2 cos100t (V) khi C=C1=

v in tr thun ca on mch l A. ZL=300 ;R=100 B. ZL=100 ;R=300 C. ZL=200 ;R=200 D. ZL=250 ;R=200 Cu 13(H - 2010): t in p xoay chiu c gi tr hiu dng khng i, tn s 50Hz vo hai u on mch mc ni tip gm in tr thun R, cun cm thun c t cm L v t in c in dung C thay i c. iu chnh in dung

104 (F )v C=C = 104 2 4 2

(F)th mch in c cng cng sut P=200W.cm khng

104 104 F hoc F th cng sut tiu th trn on mch u c gi tr bng nhau. Gi tr ca L bng 4 2 1 2 1 3 H. H. A. B. H . C. D. H . 2 3 Cu 14: Cho mch in xoay chiu RLC mc ni tip. Bit L = 318mH; C = 17 F ; in p hai u mch lC n gi tr

u = 120 2 cos(100t / 4)(V) ; cng dng in trong mch c biu thc: i = 1,2 2 cos(100t + / 12)(A) . h s cng sut ca mch l 0,6 th phi ghp thm mt in tr R0 vi R l: A. ni tip, R0 = 15 .B. ni tip, R0 = 65 .C. song song, R0 = 25 . D. song song, R0 = 35,5 .

Cu 15: Cho mch RLC mc ni tip, bit R = 100 3 ; C = 50 / (F) ; t cm L thay i c. t vo hai u on mch in p xoay chiu n nh u = 200. cos 100t (V ) . h s cng sut cos = A.

1 2 1 3 3 2 (H) hoc (H). B. (H) hoc (H).C. (H) hoc (H).

3 / 2 th t cm L bng: 1 2 D. (H) hoc (H). 2

Cng sut v in p

Cu 1: Mch RLC ni tip gm cun dy (L,r), t in C v in tr R = 30 . t vo hai u mch hiu in th u= 50 cos(100 t) (V) th UR= 30V, UC= 80 V, Ud= 10 V. Cng sut tiu th ca on mch l: A. 20 W. B. 30 W. C. 40 W. D. 50 W. Cu 2: Cho mch in xoay chiu nh hnh v 1. Bit UAM = 5V; UMB = 25V; UAB = 20 2 V. H s cng sut ca mch c gi tr l L,r R M A. 2 /2. B. 3 /2. C. 2 . D. 3 . (HV.1) B A Cu 3: Cho on mch RC: R = 15 . Khi cho dng in xoay chiu i = I0cos100 t (A) qua mch th in p hiu dng hai u mch AB lUAB = 50V; UC = 4UR/3. Cng sut mch l A. 60W. B. 80W. C. 100W. D. 120W. Cu 4: Cho on mch nh hnh v 2. Cun dy thun cm: U AN = 200V; UNB = 250V; uAB = 150 2 cos100 t (V). H s cng sut ca on mch l C R L (HV.2) A. 0,6. B. 0,707. A B C. 0,8. D. 0,866. M N Cu 5 : Mt on mch ni tip gm mt cun dy v mt t in. Dng mt vn k c in tr rt ln o in p hai u cun dy, hai u t in, hai u c mch th thy vn k ch cng mt gi tr. H s cng sut cos ca mch l A.

1 4

B.

1 2

C.

2 2

D.

3 2

Cu 6 : Mch in xoay chiu gm cun dy (L,r) mc ni tip vi t in C. lch pha ca in pgia hai u cun dy so vi cng dng in trong mch l /3. Bit UC = Ud. H s cng sut ca mch l:

cos = 0,125.

B. cos = 0,25.

C. cos = 0,5.

D. cos = 0,75

Cu 7: t in p xoay chiu c gi tr hiu dng v tn s khng i vo hai u on mch gm bin tr R mc ni tip vi t in c in dung C. Gi in p hiu dng gia hai u t in, gia hai u bin tr v h s cng sut ca on mch khi bin tr c gi tr R1 ln lt l UC1, UR1 v cos1; khi bin tr c gi tr R2 th cc gi tr tng ng ni trn l UC2, UR2 v cos2. Bit UC1 = 2UC2, UR2 = 2UR1. Gi tr ca cos1 v cos2 l: 1 1 1 1 ; cos 2 = ; cos 2 = A. cos 1 = B. cos 1 = 5 3 2 2 2 1 2 1 2 ; cos 2 = ; cos 2 = C. cos 1 = D. cos 1 = 5 5 3 5

Cc i khi r thay iCu 1: Cho mch in xoay chiu RLC mc ni tip, c in tr R bin i c. t vo hai u on mch in p xoay chiu n nh c biu thc dng u = U 0 cos t . iu chnh R cng sut tiu th cc i. Cng sut cc i c xc nh bng: A.

U2 . 4R

B.

U2 . R

C.

2 U0 . 4R

D.

2 U0 . 2R

Cu 2(H 2007): t in pu = U0sint (U0 v khng i) vo hai u on mch RLC khng phn nhnh. Bit t cm v in dung c gi khng i. iu chnh tr s in tr R cng sut tiu th ca on mch t cc i. Khi h s cng sut ca on mch bng A. 0,85. B. 0,5. C. 1. D. 1/2 Cu 3(H 2008): on mch in xoay chiu gm bin tr R, cun dy thun cm c t cm L v t in c in dung C mc ni tip. Bit in phiu dng hai u on mch l U, cm khng Z L, dung khng ZC (vi ZC ZL) v tn s dng in trong mch khng i. Thay i R n gi tr R0 th cng sut tiu th ca on mch t gi tr cc i Pm, khi

A. R0 = ZL + ZC.

B. Pm =

U2 . R0

C. Pm =

Z2 L . ZC

D. R 0 = ZL ZC

Cu 4 : Cho mch in gm mt bin tr R, mt cun dy c t cm L = 0,6/ (H) v in tr thun r = 30, mt t in c in dung C = 10-4/ (F) mc ni tip vi nhau. on mch c mc vo mt ngun in c phng trnh u = 220 2 sin(100t - 2/3) (V). iu chnh bin tr R cng sut trn R t cc i. Khi : A. R = 40 v Pmax = 605(W). B. R = 50 v Pmax = 302,5(W). C. R = 40 v Pmax = 302,5(W). D. R = 50 v Pmax = 605(W). Cu 5: Cho mch in RLC ni tip. Cun dy khng thun cm c L = 1,4/ (H) v r = 30 ; t c C = 31,8 F. R l bin tr. in p hai u on mch c biu thc: u = 100 2 cos(100 t)(V). Gi tr no ca R cng sut trn bin tr R l cc i? Gi tr cc i bng bao nhiu? Chn kt qu ng. A.R = 50 ; PRmax = 62,5W. B. R = 25 ; PRmax = 65,2W. C. R = 75 ; PRmax = 45,5W. D. R = 50 ; PRmax = 625W.

1,4 H, r = 30 ; t in c C 31,8 F ; R thay i c ; in p gia hai u on mch l u = 100 2Cu 6: Cho mch in nh hnh v. Bit cun dy c L =

=

cos100 t(V). Xc nh gi tr ca R cng sut tiu th ca mch l cc i. Tm gi tr cc i . A. R = 20 , Pmax = 120W. B. R = 10 , Pmax = 125W. C. R = 10 , Pmax = 250W. D. R = 20 , Pmax = 125W. Cu 7: Cho mch in RC ni tip. R bin i t 0 n 600 . in p gia hai u on mch l u = U 2 cos t (V). iu chnh R = 400 th cng sut to nhit trn bin tr cc i v bng 100W. Khi cng sut to nhit trn bin tr l 80W th bin tr c gi tr l A. 200 . B. 300 . C. 400 . D. 500 . Cu 8: Cho mch RLC ni tip, cun dy thun cm, R l bin tr. in p hiu dng hai u on mch bng U khng i. Khi in tr ca bin tr bng R1 v R2 ngi ta thy cng sut tiu th trong on mch trong hai trng hp bng nhau. Tm cng sut cc i khi in tr ca bin tr thay i.

U2 A. . R1 + R 2

B.

U2 2 R 1R 2

.

2U 2 C. . R1 + R 2

U 2 (R 1 + R 2 ) D. . 4R 1 R 2

Cu 9: Cho on mch mch RC ni tip, R l bin tr. t vo hai u on mch in p xoay chiu c gi tr hiu dng U = 100 2 V khng i. Thay i R. Khi cng hiu dng ca dng in t 1A th cng sut tiu th trn on mch t cc i. Tm in tr ca bin tr lc . A. 100 . B. 200 . C. 100 2 . D. 100/ 2 . Cu 10 : Cho mt on mch in xoay chiu gm mt bin tr R mc ni tip vi t in c in dung C. t vo hai u mch mt in p xoay chiu lun c biu thc u = 200 2 cos(100 t +

) V. iu chnh R sao cho cng sut tiu 12

th trn mch t ln nht v bng 200W. in dung ca t in c gi tr Cu 11: Cho mch RLC ni tip, bit ZL = 100 ; ZC = 200 , R = 50 . Mc thm mt in tr R0 vi in tr R cng sut ca mch t gi tr cc i. Cho bit cch ghp v tnh R0 ? A. Mc song song, R0 = 100 .B. Mc ni tip, R0 = 100 . C. Mc ni tip, R0 = 50 . D. Mc song song, R0 = 50 . Cu 12: Cho mch in xoay chiu gm RLC mc ni tip. Trong , L = 1/5 (H), C = 10-3/ (F), R l mt bin tr vi gi tr ban u R = 20. Mch c mc vo mng in xoay chiu c tn s f = 50(Hz). Khi iu chnh bin tr in tr gim dn th cng sut ca trn mch s: A. tng dn. B. Gim dn. C. ban u tng dn sau gim dn. D. ban u gim dn sau tng dn. Cu 13: Mt mch in xoay chiu RLC mc ni tip trong cun dy L c in tr thun r. Mi lin h gia cng sut P P P P mch v gi tr in tr R ph thuc vi nhau theo th noP ca di y?

R A B

R C

R

R D

Cng hng Cu 14: Cho mch in xoay chiu RLC mc ni tip. Cun dy gm r = 20 v L = 2/ (H); R = 80 ; t c C bin i c. in p hai u on mch l u = 120 2 cos100 t(V). iu chnh C Pmax. Tnh Pmax ? A. 120W. B. 144W. C. 164W. D. 100W. Cu 15: t mt in p xoay chiu u = 220 2 cos(100 t)(V) vo hai u on mch R,L,C khng phn nhnh c in tr thun R = 110 . Khi h s cng sut ca on mch ln nht th cng sut tiu th trong on mch l A. 115W. B. 172,7W. C. 440W. D. 460W. Cu 16: in p hiu dng hai u mt on mch RLC l U = 100V. Khi cng hiu dng ca dng in trong mch l I = 1A th cng sut tiu th trn on mch l P = 50W. Gi c nh U, R cng cc thng s khc ca mch thay i. Tnh cng sut tiu th cc i trn on mch. A. 200W. B. 100W. C. 100 2 W. D. 400W. Cu 17: Cho mch RLC ni tip, cun dy khng thun cm. Bit R = 80 ; r = 20 ; L = 2/ (H). T C c in dung bin i c. in p hai u on mch uAB = 120 2 cos(100 t)(V). in dung C nhn gi tr no th cng sut trn mch cc i? Tnh cng sut cc i . Chn kt qu ng. A. C = 100/ ( F); 120W B. C = 100/2 ( F); 144W. C. C = 100/4 ( F);100W D. C = 300/2 ( F); 164W. Cu 18: Cho mch RLC ni tip. Trong R = 100 ; C = 0,318.10-4F. in p gia hai u mch in l uAB = 200cos100 t(V). Cun dy thun cm c t cm L thay i c. Tm L Pmax. Tnh Pmax? Chn kt qu ng. A. L = 1/ (H); Pmax = 200W.B. L = 1/2 (H); Pmax = 240W.C. L = 2/ (H); Pmax = 150W.D. L = 1/ (H); Pmax = 100W Cu 19: Ln lt mc vo ngun xoay chiu (200V-50Hz) :in tr thun,cun dy thun cm,t in th cng hiu dng ca dng in qua chng ln lt u bng 2A.Mc ni tip 3 phn t vo ngun xoay chiu trn th cng sut tiu th ca mch bng: A. 200W B. 400W C. 100W D. 800W Cu20: Cho mch in xoay chiu gm in tr thun, cun dy v t in mc ni tip. in phai u mch in c tn s thay i c. Khi tn s f=f1=50 Hz v f=f2= 200Hz th h s cng sut nh nhau. Hi khi tn s bng bao nhiu th cng dng in hiu dng t cc i: A). 150Hz B). 75Hz C). 125HZ D). 100Hz Cu 21 : Mch xoay chiu RLC ni tip. Trng hp no sau y c cng hng in A. Thay i f UCmax. B. Thay i L ULmax.C. Thay i C URmax. D. Thay i R UCmax Cu 22 : Cho mch RLC mc ni tip, trong mch ang xy ra hin tng cng hng in nu ta thay i tn s ca dng in th A. I tng. B. UR tng. C. Z tng. D. UL = UC. Cu 23: Mch RLC mc ni tip c R = 100 ( ); L = 1 / (H); C =

in p xoay chiu uAB = 120 cos ( t) (V), trong tn s gc thay i c. cng sut tiu th in ca on mch cc i th tn s gc nhn gi tr A.100 (rad/s) . B. 100 (rad/s) . C. 120 (rad/s) . D. 100 (rad/s Cu 24: Mch in R1 , L1, C1 c tn s cng hng f1. Mch in R2 , L2 , C2 c tn s cng hng f2. Bit f2 = f1. Mc ni tip hai mch vi nhau th tn s cng hng s l f. Tn s f lin h vi tn s f1 theo h thc: f = 3f1. B. f = 2f1. C. f = 1,5 f1. D. f = f1. Cu 25 : Cho mch in RLC ni tip. Trong R = 10 , L = 0,1/ (H), C = 500/ ( F). in p xoay chiu t vo hai u on mch khng i u = U 2 sin(100 t)(V). u v i cng pha, ngi ta ghp thm vo mch mt t in c in dung C0, gi tr C0 v cch ghp C vi C0 l A. song song, C0 = C. B. ni tip, C0 = C. C. song song, C0 = C/2. D. ni tip, C0 = C/2.

10 4 (F). t vo hai u u on mch mt 2

Cu 26: Gia hai u on mch in (nh hnh v) c

xoay chiu:

C A

R

u=50 2 cos 100t+ V . Cun dy c in tr thun r=10 v t cm M 2

L, r N

1 H . Khi in dung ca t in bng C1 th cng hiu dng ca dng in trong mch cc i v bng 1A. 10 Gi tr ca R v C1 ln lt bng L= 2.10-3 10-3 10-3 F C. R=40 ; C1 = F D. R=50 ; C1 = F Cu 27: Mch RLC ni tip c R= 100 , L= 2 / (H). t vo mch in p u = U0cos 2 ft, f thay i c. Khi f = 50 Hz th i chm pha /3 so vi u. i cng pha vi u th f c gi tr l: A. 100 Hz. B. 50 Hz. C. 25 Hz. D. 40 Hz. Cu : Mch xoay chiu RLC mc ni tip vi R = 10 , cm khng ZL = 10 ; dung khng ZC = 5 ng vi tn s f.:A. R=40 ; C1 = B. R=50 ; C1 =

2.10-3 F

Khi f thay i n gi tr f th trong mch c cng hng in. Ta c A. f = f. B. f > f. C. f < f. D. khng c f. Cu on mch RLC mc vo mng in tn s f1 th cm khng l 36 v dung khng l 144 . Nu mng in c tn s f2= 120Hz th cng dng in cng pha vi in p hai u on mch. Gi tr f1 l A.100Hz B. 60Hz C. 50Hz D. 90Hz Cu : on mch gm in tr R = 226 , cun dy c t cm L v t c in dung C bin i mc ni tip. Hai u on mch c in p tn s 50Hz. Khi C = C 1 = 12 F v C = C2 = 17 F th cng dng in hiu dng qua cun dy khng i. trong mch xy ra hin tng cng hng in th L v C0 c gi tr l A. L = 7,2H; C0 = 14 F .B. L = 0,72H; C0 = 1,4 F .C. L = 0,72mH; C0 = 0,14 F .D. L = 0,72H; C0 = 14 F . Cu 6(C 2007): Ln lt t in p xoay chiu u = 52sin(t)vi khng i vo hai u mi phn t: in tr thun R, cun dy thun cm (cm thun) c t cm L, t in c in dung C th dng in qua mi phn t trn u c gi tr hiu dng bng 50 mA. t in p ny vo hai u on mch gm cc phn t trn mc ni tip th tng tr ca on mch l A. 3 100 . B. 100 . C. 2 100 . D. 300 . Cu 7(C 2007): Mt on mch in xoay chiu gm in tr thun R, cun dy thun cm (cm thun) c t cm L v t in c in dung C mc ni tip, trong R, L v C c gi tr khng i. t vo hai u on mch trn in p u = U0sint, vi c gi tr thay i cn U 0 khng i. Khi = 1 = 200 rad/s hoc = 2 = 50 rad/s th dng in qua mch c gi tr hiu dng bng nhau. cng dng in hiu dng qua mch t cc i th tn s bng A. 100 rad/s. B. 40 rad/s. C. 125 rad/s. D. 250 rad/s. Cu 51(H 2009): t in p xoay chiu u = U0cost c U0 khng i v thay i c vo hai u on mch c R, L, C mc ni tip. Thay i th cng dng in hiu dng trong mch khi = 1 bng cng dng in hiu dng trong mch khi = 2. H thc ng l

A. 1 2=

.

B. 1 + 2=

.

C. 1 2=

.

D. 1 + 2=

N TP MY IN My pht in 1 phaCu : Mt my pht in xoay chiu mt pha c rto gm 4 cp cc t, mun tn s dng in xoay chiu m my pht ra l 50Hz th rto phi quay vi tc l bao nhiu ? A. 3000vng/min. B. 1500vng/min. C. 750vng/min. D. 500vng/min. Cu Mt my pht in xoay chiu mt pha c phn cm gm 8 cp cc, rto quay vi tc 7 vng/s. Tn s dng in do my pht ra l: A. 60Hz B. 50Hz C. 87Hz D. 56Hz Cu Mt khung dy dn phng dt hnh ch nht c 500 vng dy, din tch mi vng 54 cm 2. Khung dy quay u quanh mt trc i xng (thuc mt phng ca khung), trong t trng u c vect cm ng t vung gc vi trc quay v c ln 0,2 T. T thng cc i qua khung dy l A. 0,27 Wb. B. 1,08 Wb. C. 0,81 Wb. D. 0,54 Wb. Cu : 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 4mWb. S vng ca mi cun dy l

A. 25vng. B. 28vng. C. 31vng. D. 35vng Cu Phn cm ca mt my pht in xoay chiu mt pha c 2 cp cc v quay c 1200 vng trong mt pht. Mt my pht in khc c 5 cp cc cn phi quay bao nhiu vng trong mt giy sut in ng n gy ra bng my pht in c 2 cp cc? A. 2 vng B. 4 vng C. 6 vng. D. 8 vng. Cu : Mt my pht in m phn cm gm hai cp cc t quay vi tc 1500 vng/min v phn ng gm hai cun dy mc ni tip, c sut in ng hiu dng 220V, t thng cc i qua mi vng dy l 5mWb. Mi cun dy phn ng gm bao nhiu vng ? A. 198 vng. B. 99 vng. C. 140 vng. D. 70 vng. Cu: Phn cm ca mt my pht in xoay chiu c 2 cp cc v quay 25 vng/s to ra hai u mt in p c tr hiu dng U = 120V. Dng ngun in my mc vo hai u mt on mch in gm cun dy c in tr hot ng R = 10 , t cm L = 0,159H mc ni tip vi t in c in dung C = 159 F . Cng sut tiu th ca mch in bng: A. 14,4W. B. 144W. C. 288W. D. 200W. Cu 4: Ni hai cc ca mt my pht in xoay chiu mt pha vo hai u on mch AB gm in tr thun R mc ni tip vi cun cm thun. B qua in tr cc cun dy ca my pht. Khi rto ca my quay u vi tc n vng/pht th cng dng in hiu dng trong on mch l 1 A. Khi rto ca my quay u vi tc 3n vng/pht th cng dng in hiu dng trong on mch l 3A. Nu rto ca my quay u vi tc 2n vng/pht th cm khng ca on mch AB l R 2R A. . B. R 3 C. 2R 3 . D. 3 3

My pht in 3 phaCu : Mt my pht in ba pha mc hnh sao c in p pha l 127V v tn s f = 50Hz. Ngi ta a dng ba pha vo ba ti nh nhau mc tam gic, mi ti c in tr thun 100 v cun dy c t cm

qua cc ti v cng sut do mi ti tiu th l A. I = 1,56A; P = 726W. B. I = 1,10A; P =750W. C. I = 1,56A; P = 242W. D. I = 1,10A; P = 250W. Cu : Trong mng in ba pha mc hnh sao, cc ti tiu th ging nhau. Mt ti tiu th c in tr l 10 , cm khng l 20 . Cng hiu dng ca dng in qua mi ti l 6A. Cng sut ca dng in 3 pha nhn gi tr l A. 1080W. B. 360W. C. 3504,7W. D. 1870W. Cu Trong mng in ba pha mc hnh sao, cc ti tiu th ging nhau. Mt ti tiu th c in tr l 10 , cm khng l 20 . Cng hiu dng ca dng in qua mi ti l 6A. in p gia hai dy pha c gi tr bao nhiu? A. 232V. B. 240V. C. 510V. D. 208V. Cu : Mt my pht in xoay chiu ba pha mc hnh sao c in p pha l 120V. Ti ca cc pha ging nhau v mi ti c in tr thun 24 , cm khng 30 v dung khng 12 (mc ni tip). Cng sut tiu th ca dng ba pha l A. 384W. B. 238W. C. 1,152kW. D. 2,304kW Cu : Mt my pht in xoay chiu ba pha mc hnh sao c in p gia dy pha v dy trung ho l 220V. Mc cc ti ging nhau vo mi pha ca mng in, mi ti gm cun dy thun cm c cm khng 8 v in tr thun 6 . Cng dng in qua cc dy pha bng: A. 2,2A. B. 38A. C. 22A. D. 3,8A. Cu : Mt my pht in xoay chiu ba pha mc hnh sao c in p gia dy pha v dy trung ho l 220V. Mc cc ti ging nhau vo mi pha ca mng in, mi ti gm cun dy thun cm c cm khng 8 v in tr thun 6 . Cng dng in qua dy trung ho bng: A. 22A. B. 38A. C. 66A. D. 0A. Cu : Mt my pht in xoay chiu ba pha mc hnh sao c in p gia dy pha v dy trung ho l 220V. Mc cc ti ging nhau vo mi pha ca mng in, mi ti gm cun dy thun cm c cm khng 8 v in tr thun 6 . Cng sut ca dng in ba pha bng: A. 8712W. B. 8712kW. C. 871,2W. D. 87,12kW.

1 H. Cng dng in i

ng cCu : Trong ng c khng ng b ba pha, ti mt thi im no , cm ng t do cun dy th nht gy ra ti tm O c gi tr cc i l B1 th cm ng t do hai cun dy kia gy ra ti tm O l: A. B2 = B3 = B1/ 2 . B. B2 = B3 = 3 B1. C. B2 = B3 = B1/2. D. B2 = B3 = B1/3.

Cu :. Gi B0 l cm ng t cc i ca mt trong ba cun dy ng c khng ng b ba pha khi c dng in vo ng c. Cm ng t do c ba cun dy gy ra ti tm stato c gi tr A. B = 0. B. B = B0. C. B = 1,5B0.* D. B = 3B0. Cu : Stato ca mt ng c khng ng b ba pha gm 6 cun dy, cho dng in xoay chiu ba pha tn s 50Hz vo ng c. T trng ti tm ca stato quay vi tc bng bao nhiu? A. 3000vng/min. B. 1500vng/min.* C. 1000vng/min. D. 500vng/min. Cu : Stato ca mt ng c khng ng b ba pha gm 9 cun dy, cho dng in xoay chiu ba pha tn s 50Hz vo ng c. Rto lng sc ca ng c c th quay vi tc no sau y? A. 3000vng/min. B. 1500vng/min. C. 1000vng/min. D. 900 vng/min.* Cu Mt ng c khng ng b ba pha c cng sut 11,4kW v h s cng sut 0,866 c mc theo kiu hnh sao vo mch in ba pha c in p dy l 380V. Ly 3 1,732. Cng hiu dng ca dng in qua ng c c gi tr l: A. 35 ampe; B. 105 ampe; C. 60 ampe; D. 20ampe; Cu : Mt ng c in xoay chiu c in tr dy cun l 32 , khi mc ng c vo mch in c in p hiu dng 200V th sn ra mt cng sut 43W. Bit h s cng sut ca ng c l 0,9. Cng dng in hiu dng qua ng c l: A. I = 0,25 ampe; B. 0,5 ampe; C. 2,5 ampe; D. 1 ampe. Cu . Mt ng c khng ng b ba pha mc theo kiu hnh sao. Bit in p dy l 381 V, cng dng Id = 20 A v h s cng sut mi cun dy trong ng c l 0,80. Cng sut tiu th ca ng c l A. 3 520 W. B. 6 080 W. C. 10 560 W. D. 18 240 W. Cu : Mt ng c khng ng b ba pha c mc theo hnh tam gic. Ba nh ca tam gic ny c mc vo ba dy pha ca mt mng in ba pha hnh sao vi in p pha hiu dng 220/ 3 V. ng c t cng sut 3kW v c h s cng sut cos = 10/11. Tnh cng dng in hiu dng qua mi cun dy ca ng c. A. 10A. B. 2,5A. C. 2,5 2 A. D. 5A. Cu : Mt ng c in mc vo mng in xoay chiu c in p hiu dng 220V tiu th cng sut 2,64kW. ng c c h s cng sut 0,8 v in tr thun 2 . Hiu sut ng c bng: A. 85%. B. 90%. C. 80%. D. 83%. 2.221.Mt ng c in xoay chiu sn ra mt cng sut c hc 100kW v c hiu sut 80%. Mc ng c vo mng in xoay chiu ng nh mc th in nng tiu th ca ng c trong mt gi l: 80 kW h 100 kWh 125 kWh 360 MJ Cu : Mt ng c in xoay chiu tiu th cng sut 2kW v c hiu sut 75%. Cng c hc hu ch do ng c sinh ra trong 20 pht bng: A. 180J. B. 1800kJ. C. 1800J. D. 180kJ. Cu 44: 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: 220 V 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 56: Mt ng c in xoay chiu khi hot ng bnh thng vi in p hiu dng 220 V th sinh ra cng sut c hc l 170 W. Bit ng c c h s cng sut 0,85 v cng sut ta nhit trn dy qun ng c l 17 W. B qua cc hao ph khc, cng dng in cc i qua ng c l A. 1 A. B. 3 A. C. 2 A. D. 2 A. Cu 65(H - 2010): Ni hai cc ca mt my pht in xoay chiu mt pha vo hai u on mch AB gm in tr thun R mc ni tip vi cun cm thun. B qua in tr cc cun dy ca my pht. Khi rto ca my quay u vi tc n vng/pht th cng dng in hiu dng trong on mch l 1 A. Khi rto ca my quay u vi tc 3n vng/pht th cng dng in hiu dng trong on mch l 3 A. Nu rto ca my quay u vi tc 2n vng/pht th cm khng ca on mch AB l A. 2 R 3 . B.

2R . 3

C. R 3 .

D.

R . 3

Cu Mt ng c khng ng b ba pha hot ng bnh thng khi in p hiu dng gia hai u mi cun dy l 220V. Trong khi ch c mt mng in xoay chiu ba pha do mt my pht ba pha to ra, sut in ng hiu dng mi pha l 127V. ng c hot ng bnh thng th ta phi mc theo cch no sau y? A. Ba cun dy ca my pht theo hnh tam gic, ba cun dy ca ng c theo hnh sao.

B. Ba cun dy ca my pht theo hnh tam gic, ba cun dy ca ng c theo tam gic. C. Ba cun dy ca my pht theo hnh sao, ba cun dy ca ng c theo hnh sao. D. Ba cun dy ca my pht theo hnh sao, ba cun dy ca ng c theo hnh tam gic. Cu : Mt ng c 200W- 50V, c h s cng sut 0,8 c mc vo hai u th cp ca mt my h p c t s gia s vng dy cun s cp v th cp bng k = 5. Mt mt nng lng trong my bin th l khng ng k. Nu ng c hot ng bnh thng th cng hiu dng trong cun dy s cp l A. 0,8A. B. 1A. C. 1,25A. D. 2A

BIN THCu 16(H 2007): Mt my bin th c cun s cp 1000 vng dy c mc vo mng in xoay chiu c in p hiu dng 220 V. Khi in p hiu dng hai u cun th cp h l 484 V. B qua mi hao ph ca my bin th. S vng dy ca cun th cp l A. 2500. B. 1100. C. 2000. D. 2200. Cu 13: t vo hai u cun s cp ca mt my bin p l tng (b qua hao ph) mt in p xoay chiu c gi tr hiu dng khng i th in p hiu dng gia hai u cun th cp h l 100 V. cun th cp, nu gim bt n vng dy th in p hiu dng gia hai u h ca n l U, nu tng thm n vng dy th in p l 2U. Nu tng thm 3n vng dy cun th cp th in p hiu dng gia hai u h ca cun ny bng A. 110 V. B. 100 V. C. 220 V. D. 200 V. Cau : Cuon th cap cua may bien the co 1500 vong. T thong bien bien trong loi bien the co tan so 50Hz va gai tr cc ai 0,55mWb. ien ap hai au cuon day th cap e h co gia tr hieu dung la : A .220 V B.110 V C.199V D.199 2 V Cu 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 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. Mt bin th c hao ph bn trong xem nh khng ng k, khi cun 1 ni vi ngun xoay chiu U1 = 110V th in p o c cun 2 l U2 = 220V. Nu ni cun 2 vi ngun U1 th in p o c cun 1 l A. 110 V. B. 45V. C. 220 V . D. 55 V . Cu : Mt my bin th dng trong my thu v tuyn c cun s cp gm 1000 vng, mc vo mng in 127V v ba cun th cp ly ra cc in p 6,35V; 15V; 18,5V. S vng dy ca mi cun th cp ln lt l: 71vng, 167vng, 207vng 71vng, 167vng, 146vng 50vng, 118vng, 146vng 71vng, 118vng, 207vng Cu : Mt my bin p l tng c t s vng dy cun s cp v th cp l 2:3. Cun th cp ni vi ti tiu th l mch in xoay chiu gm in tr thun R = 60 , t in c in dung C = khng L =

103 F . cun dy thun cm c cm 12 3

nhit trn ti tiu th l A. 180W. B. 135W.

0, 6 3 H , cun s cp ni vi in p xoay chiu c gi tr hiu dng 120V v tn s 50Hz. Cng sut to C. 26,7W. D. 90W

Cu 39 : Mt my bin th c t s vng dy ca cun s cp v cun th cp l

N1 = 10. B qua mi hao ph trong N2

my. cun dy th cp cn mt cng sut P = 11kW v dng in c cng hiu dng I = 100 A. in ap hiu dng hai u cun s cp l : A.100 V B.200 V C.110 V D. 1100 V Cu : 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 25W. in p hiu dng c hai u cun th cp l A. 100V. B. 1000V. C. 10V. D. 200V. Cu : 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 25W. Cng dng in qua n bng:

A. 25A. B. 2,5A. C. 1,5A. D. 3A. Cu : 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 25W. Cng dng in mch s cp bng (coi h s cng sut trong cun s cp bng 1): A. 2,63A. B. 0,236A. C. 0,623A. D. 0,263A. n1 = 5 , hiu sut 96% nhn mt cng sut 10(kW) cun s cp v hiu th Cu 28. Mt my bin th c t s vng n2 hai u s cp l 1(kV), h s cng sut ca mch th cp l 0,8, th cng dng in chy trong cun th cp l: A. 30(A) B. 40(A) C. 50(A) D. 60(A) 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 0.0125A. Bit cun th cp mc vo mch gm mt nam chm in c r= 1 m v mt in tr R=9 m. 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. 0,19. B. 0,15. C. 0,1. D. 1,2. Bi 1: mt my bin p c hiu sut 90%. cng sut ca mch s cp l 4kW , cng dng in v in p cun th cp l 10A v 360V. h s cng sut ca cun th cp l : A 0.12 B 1 C 0.001 D p s khc Bi 2:mt my bin p gm: cun s cp c 1000 vng, cun th cp c 2000 vng. mc cun s cp vo in p 100V. khi cun th cp h o c in p l 199V. t s gia cm khng v in tr thun ca cun s cp l A 199 B 9.96 C 1.01 D p s khc Bi 3 : mt my bin p gm cun s cp c 2000 vng c in tr thun R v t cm L, cun th cp c 4000 vng. mc cun s cp vo in p xoay chiu hiu dng 100V th t s ZL/R=9.5. thay li ca my bin p bng mt li khc c d t cm gim 100 ln so vi li c th in p hai u cun th cp l A 18.9V B 9.5V C 4.8V D p s khc

TRUYN TI IN NNGCu : in nng mt trm pht in c truyn i di in p 2kV v cng sut 200kW. Hiu s ch ca cc cng t in trm pht v ni thu sau mi ngy m chnh lch nhau thm 480kWh. Cng sut in hao ph trn ng dy ti in l A. P = 20kW.B. P = 40kW.C. P = 83kW. D. P = 100kW Cu : Mt my pht in xoay chiu c cng sut 1000kW. Dng in n pht ra sau khi tng in p ln n 110kV c truyn i xa bng mt ng dy c in tr 20 . Cng sut hao ph trn ng dy l A. 6050W. B. 5500W. C. 2420W. D. 1653W. Cu Mt dng in xoay chiu mt pha, cng sut 500kW c truyn bng ng dy dn c in tr tng cng l 4 . in p ngun in lc pht ra U = 5000V. 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 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 Ngi ta truyn ti in xoay chiu mt pha t mt trm pht in cch ni tiu th 10km. Dy dn lm bng kim loi c in tr sut 2,5.10-8 m, tit din 0,4cm2, h s cng sut ca mch in l 0,9. in p v cng sut truyn i trm pht in l 10kV v 500kW. Hiu sut truyn ti in l: A. 96,14% B. 93,75% C. 96,88% D. 92,28% Cu : Cn truyn i mtcng sut in 1200kW 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 40kV. A. 18kW. B. 36kW. C. 12kW. D. 24kW. Cu : Mt my pht in ngi ta mun truyn ti ni tiu th mt cng sut in l 196KW 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. 10kV. B. 20kV. C. 40kV. D. 30kV Cu : truyn cng sut in P = 40kW i xa t ni c in p U 1 = 2000V, ngi ta dng dy dn bng ng, bit in p ni cui ng dy l U2 = 1800V. in tr dy l

A. 50 . B. 40 . C. 10 . D. 1 . Cu Ta cn truyn mt cng sut in 1MW di mt in p hiu dng 10kV 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 6,4k . D. R 3,2k . Cu in nng mt trm in c truyn i di in p 2kV, hiu sut trong qu trnh truyn ti l H 1 = 80%. Mun hiu sut trong qu trnh truyn ti tng n H2 = 95% th ta phi A. tng in p ln n 4kV. B. tng in p ln n 8kV. C. gim in p xung cn 1kV. D. gim in p xung cn 0,5kV. Cn truyn ti in nng t A n B cch nhau 5km, ti A c in p 100kV v cng sut 5000W, in tr ca ng dy ti bng ng l R. Bit rng gim in th trn ng dy ti khng vt qu 1%. Cu : in tr R c th t gi tr ti a bng: A. 20 . B. 17 . C. 14 . D. 10 . Cu : in tr sut ca ng l 1,7.10-8( .m), tit din nh nht ca dy ng bng: A. 9,8mm2. B. 9,5mm2. C. 8,5mm2. D. 7,5mm2