Dòng điện xoay chiều mới

5/24/2018 Dng i n xoay chi u mi

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TRUNG T M B I DNG V N HA & LUYN THI I HCTN PHNG

247 INH TIN HONG TP BMT

TI LIU LUYN THI I HC MN VT L

CHNGIII: DNG IN XOAY CHIUTi liu lu hnh ni b

Hv tn: _________________________________________________NM HC: 2013-2014


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RU

LU

U

CU RCU

I

Thay i L ULcc i :

2 2

2 2C

L L C L

C

R ZZ Z Z Z Z

Z

RCU U


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MC LCBI 1: I CNG VDNG IN XOAY CHIU.................................................................. 2BI 2: MCH IN XOAY CHIU CHA MT PHN T........................................................ 8BI 3: MCH IN XOAY CHIU R, L, C NI TIP............................................................... 19

1. LIN HGIA CNG DNG IN V IN P.......................................... 212. VIT BIU THC IN P V CNG DNG IN...................................... 243. HIN TNG CNG HNG. BI TON Z1=Z2.................................................... 29

4. LCH PHA......................................................................................................... 31III. BI TP VN DNG................................................................................................ 331. LIN HGIA CNG DNG IN V IN P.......................................... 332. VIT BIU THC HIU IN THV CNG DNG IN......................... 343. HIN TNG CNG HNG. BI TON Z1=Z2.................................................... 374. LCH PHA......................................................................................................... 39

BI TP TNG HP............................................................................................................ 40BI 4: CNG SUTCC TRCNG SUT........................................................................ 54

I. TM TT L THUYT................................................................................................ 54II. CC V D ................................................................................................................... 54III. BI TP THC HNH............................................................................................. 56

BI 5:CC TRHIU IN TH............................................................................................. 64DNG 1: THAY I L L maxU ................................................................................... 65

DNG 2: THAY I C C maxU ................................................................................... 71

DNG 3: THAY I L maxU ................................................................................... 84

DNG 4: THAY I C maxU ................................................................................... 85BI TP TNG HP........................................................................................................ 90

BI 6: N TP VCCH VGIN VECT..................................................................... 98BI 7: MY BIN P V TRUYN TI IN I XA............................................................. 111BI 8: MY PHT IN -NG C IN........................................................................... 117


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CHNG III: DNG IN XOAY CHIU

Trang 2 GIO TRNH VT L LTH 2013 - 2014

BI 1: I CNGVDNG IN XOAY CHIUI. TM TT L THUYT

1. Nhc li vhm sbin thin iu ha

cos( )

-A x A

x A t

2. nh ngha Dng in xoay chiu l dng in c cng bin thin iu ha theo thi gian:

0 cos( )ii I t

i: cng dng in tc thi (A) I0: cng dng in cc i (A) : tn sgc ca i (rad/s)

22 f

T

Tng t, hiu in thxoay chiu: 0 cos( )uu U t

3. Cc gi trhiu dng Cng sut ta nhit: cho dng in xoay chiu 0 cos( )ii I t qua in trR.

Cng sut tc thi: 2 2 2 20 0cos(2 2 ) 1

cos ( )2

tP Ri RI t RI

Cng sut trung bnh:Nhit lng ta ra trn R trong thi gian dt: dQ=P.dtXt nhit lng ta ra trn R trong mt chu k(ktt=0)

2 2 20 0 0

0 00

1 2cos(2 2 ) 1 sin(2 2 ) t .

2 2 2 2

TT TRI RI RI Q idt t dt t T

T

cng sut trung bnh trong mt chu k:2

20 0, I=2

2

RI IQ QP RI vi

t T

Thc tta chxt tc dng nhit ca dng in xoay chiu vi cc khong thi gian ln hn rtnhiu chu kdao ng. Mt cch gn ng, ngi ta xem khong thi gian l bi snguynln ca chu k, v P cng l cng sut trung bnh trong khong thi gian bt k, gi l cngsut. Cng hiu dng I ca dng in xoay chiu l i lng c gi trbng cng camt dng in khng i, sao cho khi i qua cng mt in trR th cng sut tiu thtrong Rbi hai dng in l nh nhau.

0 0v U=

2 2

I UI

4. in lng chuyn qua mch

Theo nh ngha cng dng in:0

lim dq=idtt

q dqi

t dt

Trong khong thi gian tt1n t2, in lng chuyn qua tit in ngang ca dy dn l:2

1

t

t

q idt

II. CC V D1. HM IU HA VNG LNG GIC

Cu 3. Dng in chy qua mt on mch c biu thc:0

cos(100 ) A6

i I t

. Nhng thi

im cng dng in c gi trbng 0 l:

x

A-A

x0

M0

O


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TRUNG TM LUYN THI I HC TN PHNG247 INH IN HONG - BMT

GIO TRNH VT L LTH 2013 2014 Trang 3

A.1

s, k=0,1,2,..300 100

kt vi B.

1s, k=1,2,3,..

300 100

kt vi

C.1

s, k=0,1,2,..400 100

kt vi D.

1s, k=0,1,2,..

600 100

kt vi

Hng dn:Cch 1: Gii phng trnh lng gic

0 1cos(100 ) =0 1006 6 2 300 100ki I t t k t

1 1 t 0 0 0,1,2,...

300 100 3

kk k p n A.

Cch 2: ng dng mi lin hgia chuyn ng trn u v dao ng iu hA.(Vvng trn lng gic nh chng 1. HS tgii).

Cu 4. Dng in chy qua mt on mch c biu thc: 2cos100 Ai t . Trong mt giy dngin i chiuA.100 ln B.50 ln C.110 ln D.90 ln

Hng dn:

i vi dng in xoay chiu, chiu dng in lun thay i. Ngita chn mt trong hai chiu l chiu dng, th i>0 khi dngin i theo chiu dng chn, i


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Cch 2: Tnh pha dao ng: =1006

pha t

1 1= 100

600 600 6 3t s pha

0 2 v i ang gim2

Ii A

p n D.

IN LNG CHUYN QUA TIT IN THNG CA DY DN

Cu 7. Dng in chy qua mt on mch c biu thc: 5cos(100 ) A2

i t

. Tnh in lng

chuyn qua mch trong1

6chu ku tin.

A. 150

C

B. 1100

C

C. 110 C

D. 1

40 C

Hng dn:

2

1

6 6

00

5 5 1 15cos(100 t ) sin(100 ) .

2 100 2 100 2 40

T Tt

t

q idt dt t C

p n D

III. BI TP VN DNGCu 1. Dng in xoay chiu l dng inA.c tn sbin thin iu ha theo thi gian. B.c cng bin thin iu ha theo thi gian.C.c chiu bin thin tun hon theo thi gian. D.c cung cp bi bnh c quy.Cu 2. Khi nin cng hiu dng ca dng in c xy dng trn c sA.gi trtrung bnh ca dng in B.mt na gi trcc iC.khnng ta nhit so vi dng in mt chiu D.Hiu ca tn sv gi trcc iCu 3. i vi dng in xoay chiu, pht biu no sau y ng?A.Trong cng nghip, c thdng dng in xoay chiu min.B.in lng chuyn qua mt tit in thng dy dn trong mt chu kbng 0.C.in lng chuyn qua mt tit in thng dy dn trong khong thi gian bt ku bng 0.

D.Cng sut ta nhit tc thi c gi trcc i bng 2 ln cng sut ta nhit trung bnh.Cu 4. Trong cc i lng c trng cho dng in xoay chiu sau y, i lng no c dng gi trhiu dng:A.hiu in th B.chu k C.tn s D.cng sut

Cu 5. Trong cc i lng c trng cho dng in xoay chiu sau y, i lng no khng dng gitrhiu dng:A.hiu in th B.cng dng in C.tn s D.sut in ng.Cu 6. Pht biu no sau y ng?A.Khi nim cng dng in hiu dng c xy dng da vo tc dng hahc ca dng in.B.Khi nim cng dng in hiu dng c xy dng da vo tc dng nhit ca dng in.C.Khi nim cng dng in hiu dng c xy dng da vo tc dng tca dng in.D.Khi nim cng dng in hiu dng c xy dng da vo tc dng pht quang ca dng in.Cu 7. Chn cu trli sai: dng in xoay chiuA.gy ra tc dng nhit trn in tr. B.gy ra ttrng bin thin.C.c dng min, c in. D.c cng bin i theo thi gian.

Cu 8. Tc dng ca dng in xoay chiu khng phthuc vo chiu ca dng in l:A.nhit. B.hA. C.t. D.nhit v hA.Cu 9. Dng in xoay chiu v dng in khng i u c sdng A.min, c in. B.np c quy. C.in phn. D.un nng, thp sng.

iO


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Cu 10. Hiu in thgia hai u on mch c biu thc: 220 2 cos100 t Vu . Hiu in thhiu dng ca on mch l:

A.110 V B.110 2 V C.220 V D. 220 2 V Cu 11. Pht biu no sau y saikhi ni vhiu in thhiu dng:A.c ghi trn cc thit bsdng in. B.c o bng vn kxoay chiu.

C.c gi trbng gi trcc i chia 2 D.c o bng vn kkhung quay.

Cu 12. Ngun xoay chiu c hiu in th 100 2 cos100 t Vu . thit bhot ng tt nht thgi trnh mc ca thit bl:

A.100 V B.100 2 V C.200 V D. 200 2 V

Cu 13. Mt dng in xoay chiu c cng : 2 2 cos(100 ) A2

i t

. Chn pht biu sai:

A.cng hiu dng I=2 A. B.tn sf=50 Hz.

C.ti thi im t=0,15s th i t cc i. D.pha ban u2

.

Cu 14. Cng dng in trong mch khng phn nhnh c dng: 2 2 cos100 Ai t . Nu dng

ampe knhit o cng dng in ca mch trn th ampe kchgi trbao nhiu?A.I=4A B.I=2,83A C.I=2A D. I=1,41A

Cu 15. in p hai u bng n c biu thc: 100 2 cos100 t Vu . n chsng khi

100 Vu . Tnh tlthi gian n sng ti trong mt chu k.

A.1:1 B.2:3 C.1:3 D. 3:2

Cu 16. in p hai u bng n c biu thc: 100 2 cos100 t Vu . n chsng khi

100 Vu . Tnh thi gian n sng trong mt chu k.

A.1

100s B.

1

50s C.

1

150s D.

1

75s

Cu 17. in p hai u bng n c biu thc: 100 2 cos100 t Vu . n chsng khi100 Vu . Tnh thi gian n sng trong mt pht.

A.20s B.30s C.40s D. 45s

Cu 18. Mt bng n in chsng khi c 100 2 Vu c gn vo mng in c gi trhiu dng

l 200 V. Tm tlthi gian n ti v sng trong mt chu k.A.1:1 B.2:1 C.1:2 D. 3:1

Cu 19. Mt n ng c mc vo mng in xoay chiu 220 V50 Hz. Bit rng n chsng khi

hiu in thtc thi gia hai cc ca n c ln khng nhhn 155,56 V. (155,56 110 2 ).Trong mt chu k, thi gian n sng l:

A.1

100 s B.1

50 s C.1

75 s D.1

20 s

Cu 20. Mt n ng c mc vo mng in xoay chiu c tn s50 Hz. Bit rng n chsng khi

hiu in thtc thi gia hai cc ca n c ln khng nhhn 155,56 V. (155,56 110 2 ). Thi

gian n sng trong 2s l4

3s . in p hiu dng hai u bng n l:

A.220 V B.220 3 V C. 220 2 V D. 200 V

Cu 21. Biu thc dng in trong mch c dng: 4cos(8 ) A6

i t

. Vo thi im t cng

dng in tc thi l 0,7 A.Hi sau 3s gi trtc thi ca cng dng in l bao nhiu?

A.-0,7 A B.0,7 A C.0,5 A D. 0,75 A


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Cu 22. Dng in xoay chiu c biu thc: 2cos(100 ) A3

i t

. Nhng thi im no ti

cng tc thi c gi trcc tiu?

A.1

, k=1,2,3,..120 100

kt s B.

1, k=0,1,2,..

120 100

kt s

C.1

, k=1,2,3..120 100

kt s D.

1, k=0,1,2,..

120 100

kt s

Cu 23. Biu thc dng in trong mch c dng: 2 2 cos(100 ) A6

i t

. Vo thi im t cng

dng in tc thi l 0,5 A.Hi sau 0,03s gi trtc thi ca cng dng in l bao nhiu?A.0,5 A B.0,4 A C.-0,5 A D. 1 A

Cu 24. Biu thc dng in trong mch c dng: 2cos100 Ai t . Sln cng tc thi c ln i=1A trong 1s l:A.200 ln. B.400 ln. C. 100 ln. D. 50 ln.Cu 25. Biu thc dng in trong mch c dng: 4cos20 Ai t . Vo thi im t1cng dngin tc thi l i1= 2 A v ang gim. n thi im t2=t1+0,025s th cng dng in l

A. 2 2 A B. 2 3 A C.2 A D. -2 ACu 26. Dng in xoay chiu chy qua mt on mch c biu thc: 2

2 cos100 Ai t . Vo mt

thi im no , dng in ang c cng tc thi 2 2 A th sau t nht bao lu dng in c

cng tc thi 6 A ?

A.1

120s B.

1

600s C.

1

300s D.

1

150s

Cu 27. Hai dng in xoay chiu i1, i2c tn sln lt l f1=50 Hz v f2=100 Hz. Trong cng mtkhong thi gian, sln i chiu caA.dng i1gp 2 ln dng i2. B.dng i1gp 4 ln dng i2.C.dng i2gp 2 ln dng i1. D.dng i2gp 4 ln dng i1.

Cu 28. Thi im u tin ktthi im ban u, dng in 5cos(100 ) A2

i t

c gi tr2,5 A

l:

A.1

200s B.

1

300s C.

1

400s D.

1

600s

Cu 29. Mt dng in xoay chiu chy qua in tr 10R , nhit lng ta ra trong 30 pht l900kJ. Cng dng in cc i trong mch l:A.I0=0,22 A B.I0=0,32 A C.I0=7,07 A D. I0=10 A

Cu 30. in trca mt bnh nu nc l 400R . t vo hai u bnh mt hiu in thxoay

chiu th dng in qua bnh l: 2 2 cos100 Ai t . Sau 4 pht nc si. Bqua mi mt mt nng

lng. Nhit lng cung cp lm si nc l:A.6400J B.576kJ C.384kJ D. 768kJ

Cu 31. Dng in xoay chiu qua mt on mch c biu thc l: 0 cos( )i I t . Tnh tlc t=0,

in lng chuyn qua mch trong1

4chu ku tin l:

A. 0I

B. 0

2I

C. 0

2

I

D. 0

Cu 32. Dng in xoay chiu qua mt on mch c biu thc l: 0 cos( )2i I t

. Tnh tlc t=0,

in lng chuyn qua mch trong1

2 chu ku tin l:

A. 02I

B. 0

2I

C. 0

2

I

D. 0

2

I


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Cu 33. Dng in xoay chiu qua mt on mch c biu thc: 2 cos(120 ) A3

i t

. Tnh tlc

t=0, in lng chuyn qua mch trong1

6chu ku tin l:

A. 33,25.10 C B. 34,03.10 C C. 32,53.10 C D. 33,05.10 C Cu 34. (H 2007). Dng in chy qua mt on mch c biu thc: 0 sin100 ti I . Trong khong

thi gian t0 n 0,01s cng dng in tc thi c gi trbng 0,5I0vo nhng thi im

A.1 2

v300 300

s s . B.1 2

v400 400

s s C.1 3

v500 500

s s D.1 5

v600 600

s s

Cu 35. (H 2010). Ti thi im t, in p 200 2 cos 100 t2

u

, trong u tnh bng V, t

tnh bng s, c gi tr100 2 V v ang gim. Sau thi im 1

300s , in p ny c gi trl

A.-100 V B.100 3 V C. 100 2 V D. 200 VCu 36. (C 2011). Cho dng in xoay chiu c tn s50 Hz, chy qua mt on mch. Khong thi

gian gia hai ln lin tip cng dng in ny bng 0 l

A.1

25s B.

1

50s C.

1

100s D.

1

200s

Cu 37. Vo cng mt thi im no hai dng in xoay chiu 1 0 1cos( )i I t v

2 0 2cos( )i I t c cng gi trtc thi 00,5 3I nhng mt dng in ang tng, mt dng in

ang gim. Hai dng in ny lch pha nhau

A.3

B.2

3

C. D.

2


2 0 2cos( )i I t c cng gi trtc thi 00,5I nhng mt dng in ang tng, mt dng in ang

gim. Hai dng in ny lch pha nhau

A.3

B.2

3

C. D.

2


2 0 2cos( )i I t c cng gi trtc thi 00,5 2I nhng mt dng in ang tng, mt dng in

ang gim. Kt lun no sau y l ng?A.Hai dng in dao ng cng phA. B.Hai dng in dao ng ngc phA.C.Hai dng in dao ng lch pha nhau 1200. D.Hai dng in dao ng vung phA.

Cu 40. Vo cng mt thi im no in p xoay chiu trn hai phn tni tip c biu thc lnlt l: 1 0 1cos( )u U t v 2 0 2cos( )u U t c cng gi trtc thi 00,5 2U nhng mt in

p ang tng, mt in p ang gim. Hai in p ny lch pha nhau

A.3

B.2

3

C. D.

2

Cu 41. (H-2012)t in p u = 400cos100t (u tnh bng V, t tnh bng s) vo hai u on mchAB gm in trthun 50 mc ni tip vi on mch X. Cng dng in hiu dng qua on

mch l 2 A.Bit thi im t, in p tc thi gia hai u AB c gi tr400V; thi im1

400t

(s), cng dng in tc thi qua on mch bng khng v ang gim. Cng sut tiu thin ca

on mch X lA.400 W. B.200 W. C.160 W. D.100 W.


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Cu 42. (C 2013) in p hai u mt on mch l 160cos100 ( )u t V (t tnh bng s). Ti thi

im t1, in p hai u on mch c gi tr80V v ang gim. n thi im t2=t1+0,015s, in p hai u on mch c gi trbng :A.80V B.80 3 V C.40 3 V D.40V.

Cu 43. (C 2013) Cng dng in 2 2cos100 ( )i t A c gi trhiu dng bng :

A.2A B. 2 A C.2 2 A D.1A

P N1B 2C 3B 4A 5C 6B 7C 8A 9D 10C

11D 12A 13C 14C 15A 16A 17B 18C 19C 20A

21B 22B 23C 24A 25B 26A 27B 28D 29D 30C

31A 32B 33A 34D 35C 36C 37A 38B 39D 40D

41B 42B 43A

BI 2: MCH IN XOAY CHIU CHA MT PHN TI. TM TT L THUYT

1. Mch chc in trthuna)Biu thc: nu 0 cos( )ii I t

0 cos( )iu U t

b)nh lut Ohm

00

UU uI I i

R R R

in trR cho cdng in xoay chiu v dng in khng i i qua, v u cn trdngin. Cng sut ta nhit (trung bnh): 2P RI c)Gin : u v i cng phA.

2. Mch chc cun thun cma)Biu thc: nu 0 cos( )ii I t

0 cos( )2iu U t

b)nh lut Ohm

00 nhng

L L L

UU uI I i

Z Z Z

Cm khng: ( )LZ L . Cun dy thun cm cho cdng in xoay chiu v dng in

khng i i qua, chcn trdng xoay chiu, khng tiu thcng sut.

c)Gin : u nhanh pha2

so vi i.

3. Mch chc tina)Biu thc: nu 0 cos( )ii I t

0 cos( )2iu U t

b)nh lut Ohm

0

0 nh- ngC C C

UU u

I I iZ Z Z

R

u

i

L

u

i

C

u

i


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Dung khng:1

( )CZ C . Tin ngn cn dng in khng i, chcho dng in xoay

chiu iqua v cn trdng in xoay chiu, khng tiu thcng sut.

c) Gin : u chm pha2

so vi i.

4. Hthc c lp (hthc lin hgia cc gi trtc thi, c lp vi thi gian)i vi mch chc L, hoc chc C, hoc cL v C ni tiptng qut: i vi hai daong iu ha vung pha:

22

200 0

220 0

20 0

cos ( )cos( )cos( )

cos( ) sin( )sin( ) sin ( )2

iii

i ii i

iitti I t

I I

uu U t U t ut t

U U

2 2

2 20 0

1i u

I U

II. CC V D1. CNG THC NH LUT OHM

V d 1. t vo hai u mt cun cm thun L mt in p xoay chiu c gi trhiu dng U khngi v tn sf thay i. Khi f=60 Hz th cng hiu dng qua L l 2,4 A.cng hiu dngqua L bng 3,6 A th tn sca dng in phi bngA.75 Hz B.40 Hz C.25 Hz D.50 Hz

Hng d

n:

11 1 1 2 1

2 12 1 2

22 2

240 Hz

2

L

L

U U

I Z f L I f If f

I f IU UI

Z f L

p n B.

V d 2. Mt tin khi mc vo ngun 2 cos(100 ) Vu U t th cng hiu dng quamch l 2 A.Nu mc tvo ngun cos(120 0,5 ) Vu U t th cng hiu dng qua mch l

A.1,2 2 A B.1,2 A C. 2 A D.3,5 AHng dn:

1 1 1 1 1 12

2 2 22 2 2

.1001,2 2 A

.1202C

I U C I UU UI UC I

UZ I UI U C

p n A.

V d 3. on mch in xoay chiu tn sf1=60 Hz chc mt tin. Nu tn sl f2th dungkhng ca tin tng thm 20%. Tn sf2l:A.72 Hz B.50 Hz C.250 Hz D.10 Hz

Hng dn:

2 1 12 1 1 1 2

1 2

0,2 1,2 , 1,2 50 Hz1,2

CC C C C

C

Z f fZ Z Z Z f

Z f p n B.

2. QUAN HGIA CC GI TRTC THI

V d 4. (H 2011). t in p

2cosu U t vo hai u mt tin th cng dng in quan c gi tr

hiu d

ng l I. Ti th

i im t, in p hai

u tin l u v cng

dng in qua n

l i. Hthc lin hgia cc i lng l

A.2 2

2 2

1

4

u i

U I B.

2 2

2 21

u i

U I C.

2 2

2 22

u i

U I D.

2 2

2 2

1

2

u i

U I


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Hng dn:2 2 2 2 2 2

2 2 2 22 20 0

1 1 2( 2) ( 2)

i u i u i u

I U I U I U p n C.

V d 5. t vo hai u on mch chc cun cm thun mt in p xoay chiu 0 cos100u U t

V. Bit gi trin p v cng dng in ti thi im t1l 1 50 2 Vu , 1 2 Ai v ti thi

im t2l 2 50 Vu v 2 3 Ai . Gi trU0l:

A.50 V B.100 V C. 50 3 V D.100 2 V Hng dn:

2 21 12 2 2 2 20 0 0 0 0 0

2 202 2

2 2 22 20 0 00 0

1 1 1 11 2 2.2500 1

4 2 A

1 1 1 1 100 V3 2500 11

10000

i u

I U I U I I

Ui uI U UI U

p n B.

V d 6. t vo hai u mt cun cm thun c tcm0,3

H

mt in p xoay chiu. Bit in

p c gi trtc thi 60 6 V th dng in c gi trtc thi 2 A v khi in p c gi trtc thi

60 2 V th dng in c gi trtc thi 6 A . Tn sca dng in lA.120 Hz B.50 Hz C.100 Hz D.60 Hz

Hng dn:2 21 12 2 2 2 20 0 0 0 0 0

2 22 2 0

2 2 22 20 0 00 0

1 1 1 11 2 3600.6 1

8 2 2 A

1 1 1 1 120 2 V6 3600.2 1128800

i u

I U I U I I

i u UI U UI U

0

02 60 100 HzL

U

Z fL f I p n C.

V d 7. Mt hp X chcha mt trong ba phn tl in trthun, cun cm thun hoc tin. tvo hai u hp X mt in p xoay chiu cgi trhiu dng khng i nhngtn sthay i C.Khi f=50 Hz th in p trn X v dng in trong mch thi im t1c gi trln lt l:

1 100 3 Vu v 1 1 Ai , thi im t2th: 2 100 Vu , 2 3 Ai . Khi f=100 Hz th cng

dng in hiu dng trong mch l 0,5 2 A . Hp X cha

A.in trthun 100R B.Cun cm thun c tcm1

HL

C.tin c in dung410

FC

D.tin c in dung100 3

FC

Tm t

t:

1 11

2 2

1 ; 100 350 Hz

3 ; 100

i A u V f

i A u V

2 2100 0,5 2f Hz I A

/ / ?X R L C Gii

1) Khi f1=50 Hz.

a) Nu mch chcha R th: 1 2

1 2

100 3 100, v l

1 3

u uuR

i i i mch L hoc C.

b) Mch L hoc C th:


13/130



2 21 12 2 2 2 20 0 0 0 0 0

2 202 2

2 2 22 20 0 00 0

1 1 1 11 1 30000 1

4 2 A

1 1 1 1 200 V3 10000 1140000

i u

I U I U I I

Ui uI U UI U

Theo bi, hiu in thhiu dng khng i, f thay i dn n Z thay iI thay i.Nh vy, n

y ta thu c: Hiu in thhiu dng lun lunl: 100 2 VU . Cng hiu dng trong trng hp f1: I1=1 A.

2) Khi f2=100 Hz

2 1 2 12 1

0,5 2 0,707 A f1Z=ZL.

2 22 2 2

1 100 2 1 12 H

2 2 .1000,5 2L

U UZ L f L

I I f

p n B.

3. BIU THC IN P V DNG INV d 8. (H 2010). t in p 0 cosu U t vo hai u cun cm thun c tcm L th cng

dng in qua cun cm l

A. 0 cos2

Ui t

L

B. 0 cos

22

Ui t

L

C. 0 cos2

Ui t

L

D. 0 cos

22

Ui t

L

Hng dn:

Mch chc Lu nhanh pha2

so vi II chm pha2

so vi u:

0 0cos cos

2 2L

U Ui t t

Z L

p n C.

V d 9. t in p 0 cos 120 V4u U t

vo hai u mt tin th vn knhit mc song

song vi tin ch120 2 V , ampe knhit mc ni tip vi tin ch 2 2 A . Chn kt lunng:

A.in dung ca tin l1

mF7,2

, pha ban u ca dng in qua tin l4

.

B.Dung khng ca tin l 60 , pha ban u ca dng in qua tin l2

.

C.Dng in tc thi qua tin l 4cos 100 A4i t

.

D.in p cc i hai u tin l 120 2 V , dng in cc i qua tl 2 2 A .Hng dn:

3120 2 1 1060 V C= F

7,22 2C

C

UZ

I Z

Mch Ci sm pha2

so vi u: 2 cos 120 =4cos 120 A4 2 4

i I t t

p n A.


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V d 10.

thbiu din cng tc thi ca dng in xoay chiu chc cun cm thun c cmkhngZL=50 nh hnh v. Vit biu thc in p tc thi hai u cun cm.

A.50 5

60cos V3 6

u t

. B.50

60sin V3 3

u t

C.50

60cos V3 6

u t

. D.50

30cos V3 3

u t

Hng dn:1) Lp biu thc cng dng in:

I0=1,2 A

0

0 23

ang gimi

I

it

i

i tvtr 0,010

6

50tr cn bng = rad/s

2 3t sIi v

t

50

1,2cos A3 3

i t

2) Suy ra biu thc hiu in th:

Mch chc Lu sm pha2

so vi i: 050 50 5

Z cos =60cos V3 3 2 3 6L

u I t t

p n A.

V d 11.(H 2009). t in p 0 cos 100 V3u U t

vo hai u mt tin c in dung

0,2

mF. thi im in p gia hai u tin l 150 V th cng dng in trong mch l 4 A.

Biu thc ca cng dng in trong mch l

A. 4 2 cos 100 A6

i t

B. 5cos 100 A6

i t

C. 5cos 100 A

6

i t

D. 4 2 cos 100 A

6

i t

Hng dn:131 0,2.10

100 . 50CZ C

22 2 2 22

02 2 2 2 2 20 0 0 0 0

1 1501 1 4 1 5 A

50.Zc

i u i uI

I U I I I

Mch chc Ci sm pha2

so vi u: 5cos 100 A6

i t

p n B.

t (s)

i (A)

0,6

-1,2

0,01


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V d 12.t in p 0 cos 100 Vu U t vo hai u on mch chc cun cm thun c t

cm0,4

H

. Nu ti thi im t1in p l 60 V th cng dng in ti thi im t1+0,035s c

ln l

A.1,5 A. B.1,25 A. C.1,5 3 A . D. 2 2 A .Hng dn:

40LZ L

thi im t1: 1 0 1cos 100 =60V (1)u U t

0 0cos 100 = cos 1002 40 2L

U Ui t t

Z

thi im t2=t1+0,035s:

0 0 02 1 1 1cos 100 0,035 cos 100 3 cos 100 (2)40 2 40 40U U U

i t t t

T(1) v (2): 260

1,5 A 1,5 A

40

i i p n A.

V d 13.t in p 0 cos 100 Vu U t vo hai u on mch chc tin c in dung0,1

mF

. Nu ti thi im t1in p l 50 V th cng dng in ti thi im t1+0,005s l

A.-0,5 A. B.0,5 A. C.1,5 A. D.-1,5 A.

Hng dn:ZC=100

thi im t1: 1 0 1cos 100 =50V (1)u U t

0 0cos 100 = cos 1002 100 2C

U Ui t t

Z

thi im t2= t1+0,005s :

0 0 02 1 1 1cos 100 0,005 cos 100 cos100 (2)100 2 100 100U U U

i t t t

T(1) v (2): 250

0,5 A100

i p n A.

III. BI TP VN DNGCu 1. Tm pht biu sai:A.in trthun ta nhit khi c dng in i quA.B.Tin khng cho dng in mt chiu i quA.C.Cun dy khngc tc dng ngn cn dng in xoay chiu.D.Tin cho dng in xoay chiu i qua nhng cn trn.Cu 2. Tm pht biu sai:A.Khi tng tn s, in trR khng i. B.Khi tng tn s, cm khng tng.C.Khi tng tn s, in dung gim. D.Khi gim tn s, dung khng tng.Cu 3. t in p xoay chiu u vo hai u on mch chcha tin c in dung C.So vi dngin i qua t, th hiu in thuA.Nhanh pha hn i. B.Nhanh pha hoc chm pha so vi i ty gi trca C.

C.nhanh pha2

so vi i. D.Chm pha2

so vi i.

Cu 4. i vi dng in xoay chiu, khnng cn trdng in ca tin C

A.cng ln khi tn sf cng ln. B.cng nhkhi chu kT cng ln.C.cng nhkhi cng dng in cng ln. D.cng nhkhi in dung ca tC cng ln.Cu 5. Khi mc mt tin vo mng in xoay chiu, nu tn sca dng in xoay chiuA.cng nhth dng in cng di qua t. B.cng ln th dng in cng kh i qua t.


16/130



C.cng ln th dng in cng di qua t. D.bng 0 th dng in qua tc cng ln nht.Cu 6. Tm pht biu ngvkhnng cn trca cun cm i vi dng in xoay chiuA.Dng in c tn scng nhcng bcn trnhiuB.Dng in c tn scng ln cng t bcn tr.C.Cun cm ngn cn hon ton dng in xoay chiu.D.Dng in c tn scng ln cng bcn trnhiu.Cu 7. Khi tn sdng in xoay chiu chy qua on mch chcha cun cm tng ln 4 ln th cmkhng ca cun cmA.tng ln 2 ln B.tng ln 4 ln C.gim i 2 ln D.gim i 4 lnCu 8. Chn pht biu sai:

A.Trong on mch chcha tin, dng in bin thin sm pha2

so vi hiu in th.

B.Trong on mch chcha tin, dng in bin thin nhanh pha2

so vi hiu in th.

C.Trong on mch chcha cun cm, dng in bin thin chm pha2

so vi hiu in th.

D.Trong on mch chcha cun cm, dng in bin thin sm pha 2

so vi hiu in th.

Cu 9. Cho dng in xoay chiu qua in trthun th hiu in thtc thi gia hai u in trA.chm pha so vi dng in B.nhanh pha so vi dng in

C.cng pha vi dng in. D.lch pha2

so vi dng in.

Cu 10. t in p 0 cos 100 (V)3u U t

vo hai u mt cun cm thun c tcm

1

2 H

. thi im in p giu hai u cun cm l 150V th cng dng in trong mch l 4A.Gi trcng dng in hiu dng trong mch l

A.4 A B. 4 3 A C. 2,5 2 A D.5 ACu 11. Vi UR, UL, UC, uR, uL, uCl cc in p hiu dng v tc thi hai u in trthun R. cunthun cm L v tin C, I v I l cng dng in hiu dng v tc thi qua cc phn t. Biuthc khng ngl:

A. RU

IR

B. Ru

iR

C. L

L

UI

Z D. L

L

ui

Z

Cu 12. Chn biu thc ng:

A. Ru

Ri

B. LL

uZ

i C. CC

uZ

i D.tt cu sai.

Cu 13. (C 2010).t in p xoay chiu 0 cosu U t vo hai u on mch chc in trthun.

Gi U l in p hiu dng gia hai u mch, i, I0v I ln lt l gi tr tc thi, gi trcc i v gi trhiu dng ca cng dng in trong mch. Hthc no sau y sai?

A.0 0

0U I

U I B.

0 0

2U I

U I C. 0

u i

U I D.

2 2

2 20 0

1u i

U I

Cu 14. t in p xoay chiu 0 cosu U t vo hai u on mch chc cun dy thun cm. Gi

U l in p hiu dng gia hai u mch, i, I0v I ln lt l gi tr tc thi, gi trcc i v gi trhiudng ca cng dng in trong mch. Hthc no sau y sai?

A.0 0

0U I

U I B.

0 0

2U I

U I C.

2 2

2 22

u i

U I D.

2 2

2 20 0

1u i

U I

Cu 15. t in p xoay chiu0

cosu U t vo hai u on mch chc tin. Gi U l in p

hiu dng gia hai u mch, i, I0v I ln lt l gi tr tc thi, gi trcc i v gi trhiu dng cacng dng in trong mch. Hthc no sau y sai?


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A.0 0

0U I

U I B.

0 0

2U I

U I C.

2 2

2 22

u i

U I D.

2 2

2 20 0

1u i

U I

Cu 16. Mc tin c in dung310

2 F

vo ngun xoay chiu c in p 120 2cos100 (V)u t .

Schampe kmc ni tip vi tin lA.4 A B.5 A C.6 A D.7 A

Cu 17. t hiu in th 200cos100 (V)u t vo hai u in trthun R=20 . Cng sut ta

nhit trn R lA.1000 W B.500 W C.1500 W D.1200 W

Cu 18. Hiu in thu v cng dng in i trong mch in chc in trthun R

A.cng phA. B.lch pha2

. C.lch pha2

. D.lch pha .

Cu 19. Mc tin c in dung 10 F vo mng in xoay chiu c tn s50 Hz. Dung khng ca tin lA.31,8 . B.3,18 . C.0,318 . D.318,3 .

Cu 20. Dng in xoay chiu qua cun dy c tcm1

H

, trong mt pht dng in i chiu

6000 ln. Cm khng ca cun dy lA.100 . B.200 . C.150 . D.50 .


2 F

vo ngun xoay chiu c in p

100 2 cos 100 (V)4

u t

. Cng dng in hiu dng trong mch c gi trl

A.4 A B.5 A C.6 A D.7 A

Cu 22. Mch in xoay chiu chgm mt phn tl in trthun, cun dy thun cm hoc tin.

Bit biu thc in p v cng dng in ln lt l 40 2cos100 (V)u t v

2 2 cos 100 (A)2

i t

. l phn tno?

A.C. B.L. C.R. D.C hoc L.Cu 23. Mch in xoay chiu chgm mt phn tl in trthun, cun dy thun cm hoc tin.

Bit biu thc in p v cng dng in ln lt l 220 2cos100 (V)u t v

2 2 cos100 (A)i t . l phn tno? C gi trbng bao nhiu?

A.R=100 B.R=110 . C.1

L H

D.310

2C F

.


2 F

vo ngun xoay chiu c in p

20cos 100 (V)6

u t

. Cng sut ca mch l

A.100 W. B.40 W. C.50 W. D.0.

Cu 25. Mc in trthun R=100 vo mng in xoay chiu 220 V50 Hz. Tnh nhit lng ta ratrn R trong 1 giA.17 424 J. B.17 424 000 J. C.1 742 400 J. D.174 240 J.


Bit biu thc in p v cng dng in ln lt l2

200cos 100 (V)

3

u t

v

2cos 100 (A)6

i t

. l phn tno? C gi trbng bao nhiu?


18/130



A.R=100 B.R=110 . C.1

L H

D.

410C F

.


Bit biu thc in p v cng dng in ln lt l2

200cos 100 (V)3

u t

v

2cos 100 (A)6i t

. l phn tno? C gi trbng bao nhiu?

A.R=100 B.R=110 . C.1

L H

D.410

C F

.

Cu 28. Mch in c hiu in thhiu dng U=200 V. Cng dng in hiu dng qua mch khimc ni tip R1=20 v R2=30 lA.4,4 A. B.4,44 A. C.4 A. D.0,4 A.

Cu 29. Mch in c hiu in thhiu dng U=200 V. Cng dng in hiu dng qua mch khimc song song R1=20 v R2=30 lA.1,667 A. B.16,67 A. C.166,7 A. D.0,1667 A.

Cu 30. Mc cun dy thun cm c tcm2

H vo ngun xoay chiu c in p

100 2 cos 100 (V)2

u t

. Pha ban u ca cng dng in l

A.2i

B. 0i C. 2i

D. i

Cu 31. t vo hai u cun thun cm L mt hiu in thxoay chiu c gi trhiu dng U=220 Vkhng i v tn sf c ththay i C.Khi f=60 Hz th dng in i qua cun cm c cng hiudng 2,4 A.dng in qua cun cm c cng hiu dng 7,2 A th tn sdng in lA.180 Hz. B.120 Hz. C.60 Hz. D.20 Hz.

Cu 32. Mc cun dy thun cm L vo mng in xoay chiu 127 V50 Hz. Dng in cc i quacun dy l 10 A.tcm L lA.L=0,04 H. B.L=0,057 H. C.L=0,08 H. D.L=0,114 H.

Cu 33. Dng in 2cos100 (A)i t qua in trR=20 . Biu thc in p hai u R l

A. 40cos 100 (V)2

u t

B. 40 2 cos 100 (V)2

u t

C. 40cos100 (V)u t D. 40 2 cos 100 (V)u t

Cu 34. Mch in chc cun cm thun1

L H

, biu thc dng in trong mch c dng

2cos100 (A)i t . Tnh cm khng ZLv vit biu thc hiu in thhai u mch in.

A.ZL=100 , 200cos 100 (V)2

u t

B.ZL=100 , 200cos 100 (V)2

u t

C.A.ZL=100 , 200cos 100 (V)u t D.A.ZL=200 , 200cos 100 (V)2

u t

Cu 35. t hiu in thxoay chiu 0 cos 100 uu U t vo hai u cun cm thun c t

cm1

4L H

th dng in trong mch c biu thc 2cos 100 (A)

6i t

. Nu thay cun cm

trn bng tin c in dung310

2

F

th biu thc cng dng in l

A. 2,5cos 100 (A)2

i t

B. 2,5cos 100 (A)6

i t


19/130



C.5

2,5cos 100 (A)6

i t

D.5

0,25cos 100 (A)6

i t

Cu 36. t hiu in thxoay chiu 100cos 100 (V)2

u t

vo hai u cun cm thun c

tcm0,4

L H

. Vit phng trnh dng in qua mch khi . Nu thay cun cm trn bng in tr

R=20 th cng sut ta nhit trong mch l bao nhiu?

A. 2,4cos 100 (A)i t ; P=250 W. B. 2,5cos 100 (A)i t ; P=250 W.

C. 2cos 100 (A)i t ; P=250 W. D. 2,5cos 100 (A)i t ; P=62,5 W.

Cu 37. t hiu in thxoay chiu 0 cos 100 uu U t vo hai u cun cm thun c t

cm1

L H

th dng in trong mch c biu thc 5 2 cos 100 (A)3

i t

. Nu thay cun cm

trn bng in trR=50 th biu thc cng dng in l

A.

5

10cos 100 (A)6i t

B. 10 2 cos 100 (A)6i t

C.5

10 2 cos 100 (A)6

i t

D.5

10 2 cos 100 (A)6

i t

Cu 38. t vo hai u cun thun cm1

L H

mt hiu in th 200cos 100 (V)3

u t

th

biu thc ca cng dng in trong mch l

A. 2cos 100 (A)3

i t

B. 2cos 100 (A)6

i t

C. 2cos 100 (A)6i t

D. 2cos 100 (A)3i t

Cu 39. Dng in 4 2 sin 100 (A)i t qua mt ng dy thun cm c tcm1

20L H

.

Biu thc hiu in thhai u ng dy l

A. 20 2 cos 100 (V)u t B. 20 2 cos 100 (V)u t

C. 20 2 cos 100 (V)2

u t

D. 20 2 cos 100 (V)2

u t

Cu 40. t hiu in thxoay chiu 0 cos 4u U t

vo hai u on mch chcha tin c

in dung1

7200C F

. Ti thi im t1th in p v cng dng in c gi trln lt l:

1 60 2 Vu v 12

A2

i , ti thi im t2 th 1 60 3 Vu v 1 0,5 Ai . Tn s dng in l

A.50 Hz B.60 Hz C.25 Hz D.30 Hz

Cu 41. Mt hp kn X chcha mt trong ba phn t: in trthun R hoc cun dy thun cm L hoc

tin C.t vo hai u X mt in p xoay chiu c biu thc 0 cos 2u U ft vi tn sf thay i

C.Khi f=50 Hz th in p v dng in trong mch thi im t1c gi trln lt l

1 100 3 Vu v 1 1 Ai , thi im t2th 2 100 Vu v 2 3 Ai . Khi f=100 Hz th cng

dng in hiu dng trong mch l2

A2

. Hp X cha


20/130



A.in trthun R=100 . B.cun cm thun c1

L H

C.tin c in dung410

C F

. D.cun cm thun c100

3L H

Cu 42. (H 2009). t in p 0 cos 100 (V)3u U t

vo hai u mt tin c in dung

4210( )F

. thi im in p gia hai u tin l 150 V th cng dng in trong mch l 4 A.

Biu thc ca cng dng in trong mch l

A. 4 2 cos 100 (A)6

i t

B. 5cos 100 (A)6

i t

C. 5cos 100 (A)6

i t

D. 4 2 cos 100 (A)6

i t

Cu 43. (H 2009).t in p 0 cos 100 (V)3u U t

vo hai u mt cun cm thun c t

cm1

(H)2

. thi im in p gia hai u cun cm l 100 2 V th cng dng in qua cun

cm l 2 A.Biu thc ca cng dng in qua cun cm l

A. 2 3 cos 100 (A)6

i t

B. 2 3 cos 100 (A)6

i t

C. 2 2 cos 100 (A)6

i t

D. 2 2 cos 100 (A)6

i t

Cu 44. (H 2010). t in p 0 cosu U t vo hai u on mch gm in trthun R, cun cm

thun c tcm L v tin c in dung C mc ni tip. Gi i l cng dng in tc thi trongmch, u1, u2, u3ln lt l in p tc thi gia hai u in tr, gia hai u cun cm v gia hai u tin. Hthc ngl

A.2

2 1

ui

R LC

B. 3i u C C.1ui

R D. 2

ui

L

Cu 45. (H 2010). t in p 0 cosu U t vo hai u cun cm thun c tcm L th cng

dng in qua cun cm l

A. 0 cos2

Ui t

L

B. 0 cos

22

Ui t

L

C. 0 cos2

Ui tL

D. 0 cos22

Ui tL

Cu 46. (C 2010). t in p 0 cosu U t vo hai u cun cm thun c tcm L. Ti thi

im in p gia hai u cun cm c ln cc i th cng dng in qua cun cm bng

A. 0

2

U

LB. 0

2

U

L. C. 0

U

L. D.0.

Cu 47. (H 2011). t in p 2cosu U t vo hai u mt tin th cng dng in quan c gi trhiu dng l I. Ti thi im t, in p hai u tin l u v cng dng in qua n li. Hthc lin hgia cc i lng l

A.2 2

2 2 12u iU I

B.2 2

2 2 1u iU I . C.

2 2

2 2 14u iU I

. D.2 2

2 2 2u iU I .


21/130



Cu 48. (H 2012). Khi t vo hai u mt cun dy c tcm0,4

H

mt hiu in thmt chiu

12V th cng dng in qua cun dy l 0,4 A.Sau , thay hiu in thny bng mt in p xoaychiu c tn s50 Hz v gi trhiu dng 12 V th cng dng in hiu dng qua cun dy bngA.0,30 A B.0,40 A C.0,24 A D.0,17 A

Cu 49. (H 2013). t in p xoay chiu 2 cos (V)u U t vo hai u mt in trthun R=110

th cng dng in qua in trc gi trhiu dng bng 2 A.Gi trca U bng

A.220 V B.220 2 V C.110 V D.110 2 V Cu 50. (H 2013). t mt in p xoay chiu c gi trhiu dng khng i v tn sf thay i cvo hai u mt cun cm thun. Khi f=50 Hz th cng dng in qua cun cm c gi trhiu dngbng 3 A.Khi f=60 Hz th cng dng in qua cun cm c gi trhiu dng bngA.3,6 A B.2,5 A C.4,5 A D.2,0 A

p n:1C 2C 3D 4D 5C 6D 7B 8D 9C 10C 11D 12A 13D 14B 15B 16C 17A 18A 19D 20A

21B 22C 23B 24D 25C 26C 27D 28C 29B 30D 31D 32B 33C 34B 35C 36B 37D 38C 39B 40D

41B 42B 43A 44C 45C 46D 47D 48C 49A 50B

BI 3: MCH IN XOAY CHIU R, L, C NI TIP

I. TM TT L THUYT1. Mch R, L, C

a) Cc biu thc

0

0 0

0

cos( )

Gi s: cos( ) th cos( )

2cos( )

2

R R i

i L L i

C C i

u U t

i I t u U t

u U t

0

0 0 0 0

cos( )

hoc (1)

CR L u

R L C R L C

uu uu U t

U U U U U U U U

iLR C

u


22/130



b) Gin

vect

(1) = (2)R L C R LC

LC

U U U U U U

U

(2) l cch nhm tng vectn gin nht, tuy nhin ty theo tng biton, c thta phi nhm:

RL CU U U (cun dy c in trhot ng)RC LU U U (vn kmc vo on cha R v C)

c) Lin hcc in p, tng tr

22 2 2 2

R LC R L C U U U U U U

t

2 22 2 2 2 2 2 2 IL C L C U I R IZ IZ I R Z Z Z

22

L CZ R Z Z

d) nh lut Ohm

0 0 0 0

0

C R L C R L

L C L C

U U U U U U UU

I IZ R Z Z Z R Z Z

Lu : cR L

L C

uu ui

R Z Z

e) Gc lch pha gia u v i: (rad)

tan = = vi , -2 2

L C L C u i

R

U U Z Z

U R

Ngoi ra: cos RU R

U Z

2. Hin tng cng hng in

a) iu kin cng hng0 0 0

1 1h ng Z , f=

2L Ccng Z

LC LC

Vi ZL0, ZC0l gi trca cm khng, dung khng khi xy ra hin tngcng hng. u, i cng pha: =0; tan=0; cos=1

min maxU

Z R IR

maxR

U U

b) Bi ton Z1=Z2Xt bi ton: t in p 2cos uu U t vo hai u on mch R, L, C.Vi U khng i,chc duy nht mt i lng bin i l , L, hoc C.Khi , tn ti hai gi trca bin s: Z1=Z2 thay i - t bin s: x=

2 2 1 1 2 2

1 2 1 1 2 21 1 2 2 1 2 1 2

1 21 2 1 2 1 2

1 2 1 2

,HS chng minh

1 1 1 1

L C L C

L C L C

L C L C L L C C

Z Z Z Z lo i t Z Z Z Z Z Z

Z Z Z Z Z Z Z Z

L L LC C C LC

2

1 2 1 2 0

1

thay i, : trung bnh nhn.khi Z Z LC

Lu : T 1 2 1 1 2 2 12

1 1, t ng t: ZL C L C L Z Z Z LC C


23/130



L thay it bin s: x=ZLVi ZCkhng i, khi x=ZL=ZL0=ZCth xy ra hin tng cng hng.

2 2 1 2

1 2 1 21 2 1 2

,HS chng minh

2L C L C

L C L C

L C L C L L C


Z Z Z Z Z Z Z

1 21 2 0

ZL thay i, Z : trung bnh cng.

2

L LL C

Zkhi Z Z Z

C thay

it bin s: x=ZC.Vi ZLkhng i, khi x=ZC=ZC0=ZLth xy ra hin tng cng hng.

2 2 1 2

1 2 1 21 2 1 2

, chng minh

2L C L C

L C L C

L C L C C C L


Z Z Z Z Z Z Z

1 21 2 0

ZC thay i, Z : trung bnh cng.

2C C

C L

Zkhi Z Z Z

Tm li:Xem Z l hm stheo bin x, ta c thbiu din tt ccc kt qutrn bng thZ=f(x). x0l im cc trca

hm Z ng vi hintng cng hng. khi: Zmin=R.

x1, x2l 2 gi trcabin sm Z1=Z2.

Nu ly x3nm ngoion [x1,x2]thZ3>Z1=Z2.Nu ly x3nm trongkhong (x1,x2)thZ3Z2


24/130



1tan 0

6 6

3L C

u i u i i

Z Z

R r

u nhanh pha

6

so vi ip n B

V d 3. t in p 100 2cos100 (V)u t vo hai u on mch gm in trthun R=30

v cc tin c in dung 11

3C mF

, 2

1C mF

mc ni tip. Cng dng in hiu dng l

A.1,00 A. B.0,25 A. C.2 A. D.0,50 A.

Hng dn:

22

1 2 1 2

10030 ; 10 50 2

50C C C C U

Z Z Z R Z Z I AZ

p n C.

V d 4. (H 2011). t mt in p xoay chiu c gi trhiu dng v tn skhng i ln ltvo hai u in trthun R, cun cm thun c tcm L, tin c in dung C th cng dng in hiu dng qua mch tng ng l 0,25 A; 0,5 A; 0,2 A.Nu t in p xoay chiu ny vohai u on mch gm ba phn ttrn mc ni tip th cng dng in hiu dng qua mch lA.0,2 A. B.0,3 A. C.0,15 A. D.0,05 A.

Hng d

n:f khng iZL, ZCkhng i. U khng i.

Xt cc on mch chcha 1 phn t: ; Z ; Z0,25 0,5 0,2L CU U UR .

Xt on mch RLC ni tip:

2 2 220,2

0,25 0,5 0,2L C

U UI A

R Z Z U U U

p n A.

V d 5. on mch gm in trR=40, cun cm thun c tcm0,8

L H

v tin c

in dung42.10

C F

mc ni tip. Dng in qua mch c biu thc: 3cos100 (A)i t . in

p hiu dng hai u on mch l

A.60 V. B.240 V. C.150 V. D.75 2 V .HS tgii. p n D.

V d 6. on mch R,L,C ni tip theo ng thtgm cun cm thun c cm khng 14, intrthun 8, tin c in dung 6. Bit in p hiu dng hai u on mch l 200 V. in phiu dng trn on gm in trv tin l

A.250 V. B.100 V. C.125 2 V . D.100 2 V .Hng dn:

2 2

22. 125 2 VRC RC C

L C

UU Z I R Z

R Z Z

p n C.

V d 7. Cho mch in xoay chiu tn s50 Hz ni tip theo ng thtgm in trthun

R=50, cun dy thun cm c tcm0,5

H

v tin c in dung0,1

mF

. Tnh lch pha

gia uRLv uLC.

A.4

B.2

C.3

4

D.

3

Hng d

n:50 ; Z 100L CZ

Tnh lch pha ca uRLso vi i: tan 14

LRL RL

Z

R

Tnh lch pha ca uLCso vi i:0

tan lim2

L CLC LC

r

Z Z

r


25/130



uRLnhanh pha3

4 2 4RL LC

p n C.

V d 8. (H 2008). Cho on mch in xoay chiu gm cun dy mc ni tip vi tin.

lch pha ca in p gia hai u cun dy so vi cng dng in trong mch l3

. in p hiu

dng gia hai u tin bng 3 ln in p hiu dng gia hai u cun dy. lch pha ca inp gia hai u cun dy so vi in p gia hai u on mch trn l

A.2

3

B.0 C.

2

D.3

Hng dn:

tan tan 3 33

LRL L

ZZ R

R

2 2 2 23 . 3.I 3. 3 2 3C RL C L C U U I Z R Z Z R R R

3 2 3 2tan 3

3 3 3 3L C

RL

Z Z R R

R R

p n A.

V d 9. on mch xoay chiu ni tip gm in trthun R, tin C v cun cm thun L. tvo hai u on mch mt in p xoay chiu n nh th in p hiu dng trn R, L, C ln lt l 60V, 120 V v 40 V. Thay C bi tin C th in p hiu dng trn tl 100 V, khi in p hiudng trn R l

A.150 V. B.80 V. C.40 V. D.20 2 V .Hng dn:Chc C thay i, R v ZLkhng i. U khng i. Mch R, L, C:

22 100 VR L CU U U U

IR 60 1120 2

R

L L L

U RU IZ Z

Mch R, L, C :U vn =100 V.

I R 12

2

RL R

L L L

U RU U

U I Z Z

2 22 2 2 2100 2 100 80 VR L C R R R U U U U U U U

p n B.V d 10. t in p 200 V 50 Hz vo hai u on mch AB gm in trthun 25 mc nitip vi on mch X. Cng dng in hiu dng qua on mch l 2A.Bit thi im t0, in

p tc thi gia hai u AB c gi tr200 V v ang tng; thi im 01

600t s , cng dng in

tc thi qua on mch bng 2A v ang gim. Tnh lch pha ca in p hai u on mch AB sovi dng in qua mch. Cng sut tiu thin ca on mch AB v on mch X.

A. ; 200 W;100 W

3

B. ; 150 W;100 W

3

C. ; 150 W;100 W6

D. ; 200 W;100 W

6

Hng dn:Gi biu thc in p hai u AB v cng dng in ln lt l:

200 2 cos 100 v i=2 2 cos 100u iu t t

Vvng trn lng gic (hc sinh tv), chng ta tm c: t0: u=200 V v u ang tng (im na di vng lng gic)

0 0ca u 2 100 100 24 4u upha k t t k

0 1600t s : i=2A v I ang gim (im na trn vng lng gic)


26/130



0 0

1ca i 2 100 100 2

4 600 12i ipha l t t l

lch pha ca u so vi i: 0 0100 2 100 2 24 12 3u i t k t l n

v - =-

2 2 3

(1) : in p chm pha

3

so vi cng dng in.

Cng sut ton mch: cos 200.2.cos 200 W3

P UI

(2).

Cng sut ta nhit trn R: 2 225.2 100 WRP RI

Cng sut tiu thca on mch X: 100 WX RP P P (3).

T(1), (2), (3) p n A.

2. VIT BIU THC IN P V CNG DNG IN

PHNG PHPCch 1: Sdng cc cng thc lin hu v i

a) Hiu in thton mch u v cng dng in i:

00 ; tan = ; =

L Cu i

U Z ZI

Z R

b) Hiu in thhai u on MN bt kMN

u v cng dng in i:

00 ; tan = ; =

MN L MN C MN MN MN u i

MN MN

U Z ZI

Z R

Cch 2: Sdng gin vectMN R MN L MN C MN U U U U

Cch 3: ng dng sphc1) Sphc

Trong mt phng Oxy, vect OM c ta

(a,b)OM Tng ng vi sphc z=a+bi, vi i: l n vo.

Dng a+bi (SHIFT24) ca sphc: z=a+bi, i=ENG Dng r (SHIFT23) ca sphc:z= r

Vi 2 2 ; =SHIFT tanb

r OM a ba

. Ta khng thc hin cc tnh ton ny, Casio Fx s

lm vic . Mc tiu phn ny l ng dng ton hc vo bi ton vt l, nn chxt cc gc

phn t thnht v tht ca mt phng ta , do vy: 0; - 2 2a

2) Tng trphc

Phn thc a ca sphc z tng tthnh phn R trong cng thc tnh tng tr.Phn o b ca sphc z tng tZLC, vi ZLC=Zl-ZC.Modun ca sphc z (r=OM) tng ttng trZ.

Ngi ta dng khi nim tng trphc va din t ln ca Z, va cha ng thng tincc thnh phn R v ZLCtrong Z.

( )L CZ R Z Z i Z

3) nh lut Ohm-phcLin hgia cc biu thc u v I trong biu din phc:

MN

MN

uui Z Z

CC V D

xO a

b


27/130



V d 1. Mt mch in xoay chiu mc ni tip gm in trthun R=15, cun thun cm ccm khng ZL= 25 v tin c dung khng ZC=10. Nu dng in qua mch c biu thc

2 2 cos 100 (A)4

i t

th biu thc in p hai u on mch l

A. 60cos 100 (V)2

u t

B. 30 2 cos 100 (V)4

u t

C. 60cos 100 (V)4

u t

D. 30 2 cos 100 (V)2

u t

Hng dn:Cch 1:Sdng cng thc tnh bin v pha ban u ca u

22

0 015 2 U 2 2.15 2 60 V60cos 100 (V)

2tan 14 4 2

L C

L Cu i u u

Z R Z Z I Z u t

Z Z

R

p n A.Cch 2: Sdng gin vect

V RU , LU , CU c di tlvi R, ZL, ZC(hstll I)ULC=UR

hnh vunggc 450u nhanh pha4

so vi I, U0gp

2 ln U0R=RI0

0 2.15.2 2 60 VU

60cos 100 =60cos 100 (V)4 4 2

u t t

Cch 3:Biu din phc SHIFTMODE4: n vradian. MODE2: chCMPLX. Tnh tng trphc: 15+(25-10)

ENG

=

p dng nh lut Ohm-phc: u i Z , ta bm: 2 24

Ans

i u va tm c (60i) sang dng r : SHIFT23= ta c:1

602

p n A.

V d 2. Mch in xoay chiu mc ni tip gm in trthun R=30, cun dy c in trhotng r=30 v cm khng ZL= 40, tin c dung khng ZC=10. Dng in qua mch c biu

thc 2cos 100 (A)6

i t

. Vit biu thc in p hai u on mch cha cun dy v tin.

A. 60cos 100 (V)

3rLCu t

B. 60cos 100 (V)

4rLCu t

C. 60 2 cos 100 (V)12rLC

u t

D.5

60 2 cos 100 (V)12rLC

u t

Hng dn: p n D.Cch 1:

22

0 030

2 U . 60 2 V5

60 2 cos 100 (V)12tan 1 sm pha so vi i

4 4

rLC L C rLC rLC

rLCL C

rLC rLC rLC

Z r Z Z I Z u t

Z Zu

r

Cch 2:v , U , U (khng v U )r L C R LC rLC UU U

Cch 3: 5( ) 30 (40 10)i (i l n v o) 60

212

rLC rLC L C rLC Z r Z Z u i Z


28/130



V d 3. t in p xoay chiu 100

2 cos 100 (V)6

u t

vo hai u mt on mch gm

cun dy thun cm c tcm1

H

v tin c in dung42.10

F

ghp ni tip. Biu thc

dng in qua mch l

A. 2cos 100 (A)2i t

B. 2cos 100 (A)2i t

C. 2 2 cos 100 (A)3

i t

D. 2 2 cos 100 (A)3

i t

Hng dn: p n C.Cch 1:

00

0

100 ; Z 50 ; R=0 Z=50 I 2 2 A2 2 cos 100

6 2Ztan lim pha i

2 2

L C

L C

R

UZ

Z i tZ

u sm so vi R

Cch 2:Vgin vec t: LCU U . Hc sinh tv.

Cch 3:1

0 (100 50) 50 2

23

uZ ENG i i

Z p n C.

V d 4. t in p xoay chiu 160cos 100 (V)12

u t


cun dy khng thun cm c tcm0,6

H

v in trhot ng R, tin c in dung

1

14 mF

ghp ni tip th mch tiu thcng sut 80W. Biu thc dng in qua mch l

A. 2cos 100 (A)6i t

B. 2 cos 100 (A)6i t

C. 2 cos 100 (A)4

i t

D. 2 cos 100 (A)4

i t

Hng dn: p n B.60 ; Z 140L CZ

2 22

2 22

22 2 20 80 12800 6400 0 80

L C

L C

U UP RI R R

Z R Z Z

PR U R P Z Z R R R

1( ) 80 (60 140)i 80 80i 2 2 cos 100 (A)6 6L C

uZ R Z Z i i i t Z

V d 5. t in p xoay chiu 10cos 100 (V)4

u t


cun dy khng thun cm c cm khng ZL=10 vin trhot ng r=10, tin c dung khngZC=30 v in trthun R=10 ghp ni tip. Vit biu thc in p hai u cun dy.

A.3

5cos 100 (V)4rL

u t

B. 200 2 cos 100 (V)6rL

u t

C. 200cos 100 (V)

6

rLu t

D. 5cos 100 (V)

4

rLu t

Hng dn:Cch 1:Dng cc cng thc lin hu v i


29/130



2 2 0

0

2 20 0

10 120 2

20 2 2 2

10 2 5 V

L C

rL L rL rL

UZ R r Z Z I A

Z

Z r Z U I Z

tan 134

2 4 4tan 14

rL rL rL

rL

L Cu i

rL u u u u

LrL rL u i

Z Z

R r

Zr

35cos 100 (V)

4rLu t

p n A.

Cch 2:Vgin vect

Nhn xt rng hnh vcn thhin c yu tcho l 0U ton mch v

yu thi l l 0rU .

V 0rU : Vcc vect Or 0; U LU c di tlvi r v ZL. 0rU .

V 0U :

0 0 0 0 tc hnh bnh hnh0 0 0(chnh l hnh vung)

0 0 0 0

U U U UU U U U

R rR r R quirR LC

c LC L c

v U U Uv

Tgin vect, dthy urLc bin bng phn na bin ca u tonmch, v urLnhanh pha hn u ton mch mt gc vung.Cch 3:biu din phC.

Tng trphc ton mch: ( ) ( )i 20 20iL CZ R r Z Z

Biu thc ca i:10

420 20

ui Ans

iZ

. Lu : cn phn bit cng i v n vo i.

Tng trphc cun dy: i 10 10irL LZ r Z Hiu in thcun dy:

3 3.(10 10 ) 5 5cos 100 (V)

4 4rLrL rLu i Z Ans i u t

Ngoi ra, bng cch tnh tng trphc c thgii c bi ton hp kn.

; Z MNMNuu

Zi i

, vi i l cng dng in tc thi dng phc: 0 ii I

Nu tnh c Z a bi , vi i l n vo, thL C

R a

Z Z b

V d 6. t in p xoay chiu 240 2 cos 100 (V)u t vo hai u mt on mch gm cun

cm thun c tcm0,6

H

, in trthun R v tin c in dung C mc ni tip. Bit biu

thc cng dng in qua mch l: 4 2 cos 100 (A)6

i t

. Gi trca R v C ln lt l

A.30 v1

mF3

B.75 v1

mF

C.150 v1

mF3

D.30 3 v1

mF3

Hng d

n:


30/130



30 3240 260 ; Z 30

3 3030 30 304 2

6

L

L C C L

RuZ i

i Z Z Z Z

31 10F

3C

C

p n D.

V d 7.t vo hai u hp kn X mt in p xoay chiu 100cos 100 (V)6u t

th cng

dng in qua mch:2

2cos 100 (A)3

i t

. Nu thay in p trn bng in p khc c biu

thc 400 2 cos 200 (V)3

u t

th cng dng in 5 2 cos 200 (A)6

i t

. X c

thcha

A.42,5 10

25 ; L ; C=R H F

B.30,7 10

; C=12

L H F

C.

41,5 1,5.10

; C=L H F

D.

5

25 ; L 12R H

Hng dn: p n B.

Khi dng in p 100cos 100 (V)6

u t

th:

100 06 502 50 (1)

23

L C

RuZ i

Z Zi

Khi dng in p 400 2 cos 200 (V)3u t

Tn sgc tng gp iZLtng gp i, ZCgim mt na

2 0400 23; Z 80

80 2 80 (2)5 2 22 6

L L

CCL C LC

Z Z Ru

i ZZi Z Z ZZ

T(1) v (2): ZL=70, ZC=120L,Cp n B.V d 8.Mch in p xoay chiu AB gm hai on mch AM v MB mc ni tip. on AM gmin trthun R=50 mc ni tip vi tin c dung khng 50 , on MB l cun dy c in trthun r v c tcm L. Bit biu thc in p trn on AM v trn on MB ln lt l

80cos100 (V)AMu t v 7200 2 cos 100 (V)12MBu t

. Gi trca r v cm khng ZLl

A.125 v 0,69 H B.75 v 0,69 HC.125 v 1,38 H D.176,8 v 0,976 H

Hng dn: p n A. Xt on AM:

Tng trphc on AM: (0 ) 50 50AM CZ R Z i i

cng dng in:80 4 2 1

50 50 5 4AM

AM

ui

iZ

Xt on mch MB:


31/130



Tng trphc MB:

7200 2 12512 125 216,506

216,506 0,689 HMB

MB

L

RuZ i

Z Li Ans

V d 9.Mch in p xoay chiu AB gm hai on mch AM v MB mc ni tip. on AM gmin trthun R1=50 mc ni tip vi cun cm c cm khng 50 , on MB gm tin c indung C v in trR2mc ni tip. Bit biu thc in p trn on AM v trn on MB ln lt l

200cos 100 (V)6AM

u t

v 5100cos 100 (V)12MB

u t

. Hscng sut ca on

mch AB lA.0,95 B.0,96 C.0,97 D.0.98

Hng dn:

200 1650 50 2

250 50 12 70,398... 0,2789...

12 25

12200 100

6 12

AMAM

AM

AM MB

uZ i i u Ans

i ZZi

u u u Ans

Thay v phi ghi kt qutrung gian ra giy nhp, ta nn bm: SHIFT 2 1 Ans =. Ta c:0,27891cosAns=0,96135p n A.

3. HIN TNG CNG HNG. BI TON Z1=Z2V d 1. t vo hai u on mch RLC ni tip mt hiu in thxoay chiu c tn sthay i. Khitn sgc ca dng in l 0th cm khng v dung khng c gi tr20 v 80 . trong mchxy ra cng hng, phi thay i tn sgc ca dng in n gi tr bngA.20 B.0,250 C.0,50 D.40

Hng d

n:

0

h-ng20 0

0 20

20

20 1 1 1 21 80 80 4 1

4

L

Cng

C

Z L

LCZ LCC

p n A.

V d 2. Mt cun dy c in trthun 100 v tcm 1

H

, ni tip vi tin c in dung

500

F

. dng in trong mch cng pha vi in p ta phi ghp ni tip vi tC mt tC1c

in dung l bao nhiu?

A. 500

F

B. 250

F

C. 125

F

D. 50

F

Hng dn:hng

1 11

1 1 1250 , mcng Cb L Cb C C Z Z Z Z Z L C F C C

p n C.

V d 3. Cho on mch in xoay chiu gm cun dy thun cm L, tin C v bin trR mc nitip. t vo hai u mch mt in p xoay chiu n nh c tn sf sao cho: 2 24 1f LC . Khi thayi R thA.in p hiu dng hai u bin trthay i. B.Tng trca mch vn khng i.C.cng sut tiu thtrn mch thay i. D.Hscng sut trn mch thay i.

Hng dn:


32/130



hng2 22

, khng i R

, thay i theo R4 1

P= , thay i theo R

cos =1, khng i R

R

cngL C

U U

Z Rf LC Z Z U

R

p n C.

V d 4. on mch xoay chiu RLC mc ni tip, in trthun ca mch R=50. Khi xy ra cnghng tn sf1th cng dng in bng 1 A.Khi tng tn sca dng in ln gp i thcng hiu dng trong mch l 0,8A.Cm khng ca cun dy khi tn sl f1bngA.25 B.50 C.37,5 D.75

Hng d

n: Khi f=f1: ZC1=ZL1, U=UR=I1R=50 V.

Khi f=2f1:

222 21 1 1

2 1 2 2 2 2 1

2

222 1 1

2

2 , Z Z 22 2 2

vn l 50 V, I 0,8 A

5050 1,5 25 p n A.0,8

C L LL L C L C L

L L

Z Z ZZ Z Z R Z R Z

U

UZ Z ZI

V d 5. Mt on mch AB gm hai on mch AM v MB mc ni tip. on mch AM gm intrthun R1mc ni tip vi tin c in dung C, on mch MB gm in trthun R2mc nitip vi cun cm thun c tcm L. t in p xoay chiu u=U0cost (U0v khng i) vohai u on mch AB th cng sut tiu thca on mch AB l 85 W, khi LC2=1 v lchpha gia uAMv uMBl 900. Nu t in p trn vo hai u on mch MB th on mch ny tiu thcng sut bngA.85 W B.135 W C.110 W D.170 W

Hng dn: t in p vo AB:

22

1 2

21 2

1 2

1 (1)

tan .tan 1 . 1

L C

C LAM MB AM MB L

ULC Z Z P

R R

Z Zu vu ng pha u Z R R

R R

t in p vo MB:2 2 2 2 so snh vi (1)

22 2 2 2 2 22 2 2 2

1 22 2 1 2

85MB L

U U U U P R I R R R P W

R RZ R Z R R R

p n A.

Cu 8. Mch xoay chiu gm R1, L1, C1mc ni tip c tn sgccng hng l 1=0. Mch R2,L2, C2mc ni tip c tn sgc cng hng l 2=20. Bit L2=3L1. Mc ni tip hai mch ny vi

nhau th tn sgc cng hng lA. 03 B. 01,5 C. 013 D. 00,5 13

Hng d

n:

Mch R1, L1, C1cng hng: 21 1 1 11 1 1

1 1(1)L L

C C

Mch R2, L2, C2cng hng: 22 2 2 22 2 2

1 1(2)L L

C C

Mch R1, L1, C1ni tip R2, L2, C2cng hng:

1 2 1 21 2 1 2

1 1 1 1 1(3)L L L L

C C C C


33/130



Thay (1) v (2) vo (3):

1 0 2 0

2 1

22, 2 0 1 0 12 2

1 2 1 1 2 2 031 1

2 31 13

3 2L LL L

L L L LL L

p n D.

Cu 9. t hiu in th 200cos100 (V)u t vo hai u on mch RLC mc ni tip c Cthay i C.Khi thay i in dung C, ngi ta thy ng vi hai gi trC1=31,8 F v C2=10,6 F

th dng in trong mch u l 1 A.Tnh hstcm v in trca mch.A.

1H; R=100L

B.

2H; R=100 3L

C.2

H; R=100L

D.1

H; R=100 3L

Hng d

n: p n C.ZC1=100 ; ZC2=300

1 21 2 1 2 1 21 2

2200 H

2C C

L C L C L

Z ZU UI I Z Z Z Z Z Z Z L

Z Z

Khi C1=31,8 F: 2 22 2

1 1

1

100 2 200 100 100L CU

Z R Z Z R R

I

4. LCH PHAPHNG PHPXt on mch AB gm hai on mch AM v MB mc ni tip. Gi AMv MBl gc lch pha cauAMv uMBso vi cng dng in i. Mt cch tng qut, AMv MBkhng phi l pha ban uca uAMv uMB.Chtrong trng hp i=0 th AMv MBmi bng vi pha ban u ca uAMv uMB.1) lch pha ca hiu in thso vi cng dng in

tan ;AM

L CAM AM u i

AM

Z Z

R

(chthay gi trcc ZL, ZC, R ca on AM)

tan ;MB

L CMB MB u i

MB

Z Z

R

(chthay gi trcc ZL, ZC, R ca on MB)

2) iu kin vung phaa) C ston hc: hsgc ca ng thng

Trong mt phng Oxy, xt ng thng d c phng trnh:y=kx

(chxt ng thng qua gc ta , v chxt cc gc phn t thnht v tht ca mt phng Oxy)

Hsgc:i

tan ; - ;2 2

yk

x k

Hai ng thng d1: y=k1x v d2: y=k2x vung gc nhau khi:

1 2 1 2tan .tan 1k k

V khi : 1 2 2

b) iu kin vung pha ca hai hiu in ththnh phn

vung pha u tan .tan 12AM MB AM MB AM MB

u

CC V DV d 1. (H 2010). Mt on mch AB gm hai on mch AM v MB mc ni tip. on mch

AM c in trthun 50 mc ni tip vi cun cm thun c tcm 1

H

, on mch MB ch

c tin vi in dung thay i C.t in pu=U0cos100t (V) vo hai u on mch AB.

O x

AM

MB


34/130



iu chnh in dung ca tin n gi trC1sao cho in p hai u on mch AB lch pha2

so

vi in p hai u on mch AM. Gi trca C1bng

A.40

( F)

B.80

( F)

C.20

( F)

D.10

( F)

Hng dn: p n B.

ZL=L=10050100

1vung pha u tan .tan 1 . 1 125

L

RL C LAM AM CZ

C

Z Z Zu Z C

R R Z

V d 2. Mt on mch AB gm hai on mch AM v MB mc ni tip. on mch AM c in

trthun 100

3 mc ni tip vi cun cm thun c cm khng ZL, on mch MB chc tindung khng 200 . t in p u=U0cost (V) vo hai u on mch AB.Bit in p gia hai u

on mch AM lch pha6

so vi in p gia hai u on mch AB.Gi trZLbng

A. 50 3 B.100 C.100 3 D.300 Hng dn:

lch pha gia in p v cng dng in

tan ;100 3 AM

L LAM AM u i

Z Z

R

200tan ;

100 3L C L

u i

Z Z Z

R

uAMlch pha6

so vi u ton mch6AMu u

(uAMnhanh pha hn u ton mch)

tan tan1

tan tan6 6 6 1 tan .tan3

AMAM i i AM AM

AM

2

22

200.100 3 1 200 30000 0 3003100 3 200

L L L

L L

Z Z ZZ Z

p n D.

V d 3. t in p xoay chiu n nh 0 cos uu U t vo hai u on mch mc ni tipgm cun dy c in trthun R, c cm khng 150 v tin c in dung C thay i C.Khi

dung khng ZC=100 v ZC=200 th dng in trong mch c pha ban u hn km nhau3

. in

trR bng

A. 50 3 B.100 C.100 3 D.50 Hng dn:

Vi 0 cos uu U t khng i, ZCcng ln th u cng chm pha so vi ii cng nhanh pha so viui2(ng trng hp ZC=200) nhanh pha hn i1(ng trng hp ZC=100)

lch pha ca i2so vi i1:2 1 3i i

lch pha gia u v i1, i2:

1

2

11 1

22 2

150 100 50tan ;

150 200 50tan ;

L Cu i

L Cu i

Z Z

R R RZ Z

R R R

M 1 2 2 11 2 3u i u i i i


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1 21 21 2

50 50tan tan

tan tan 3 50 350 503 1 tan .tan 1 .

R R R

R R

p n A.

III. BI TP VN DNG1. LIN HGIA CNG DNG IN V IN P

Cu 1. t in p xoay chiu vo hai u on mch AB theo thtgm cun dy thun cm L c cmkhng 100 3 , in trR=100 v tin C c dung khng 200 3 mc ni tip, M l im giaL v R, N l im gia R v C.Chn pht biu ng.

A.in p hai u on mch AN sm pha3

so vi in p hai u on mch AB.

B.Cng dng in trpha3


C.in p hai u on mch AN tr pha3


D.in p hai u on mch AB sm pha hn in p hai u tin l6

.

Cu 2. Gi UR, UL, Ucln lt l in p hiu dng gia hai u in trthun, cun dy thun cm vtin trong on mch xoay chiu R,L,C mc ni tip. Bit UR= UL=0,5Ucth dng in qua mchA.trpha 0,25so vi in p hai u on mch.B.trpha 0,5so vi in p hai u on mch.C.sm pha 0,25so vi in p hai u on mch.D.sm pha 0,5so vi in p hai u on mch.Cu 3. t in p 50 V 50 Hz vo on mch ni tip gm in tr40 v cun dy thun cm thin p hiu dng gia hai u cun cm l UL=30 V. tcm ca cun dy l

A.0,4

2H

B.

0,3H

C.

0,4

3H

D.

0,2H

Cu 4. Cho mch in xoay chiu khng phn nhnh RLC (cun dy thun cm). Bit8

23L CR

Z Z .

in p hiu dng gia hai u on mch l 200 V. in p hiu dng gia hai u in trR lA.180 V B.120 V C.145 V D.100 V

Cu 5. on mch in xoay chiu gm cun dy c in trthun r v hstcm L ni tip vi mttin C c mc vo mt hiu in thxoay chiu. Cng hiu dng ca dng in qua mch lI=0,2 A.Hiu in thhiu dng gia hai u on mch, hai u cun dy, hai bn tin c gi trlnlt l 120 V, 160 V, 56 V. in trthun r ca cun dy lA.128 B.480 C.96 D.300 Cu 6. on mch xoay chiu gm bin trR, tin C v cun thun cm L mc ni tip. Khi iu

chnh bin trgi trno th in p hiu dng o c trn bin tr, tin v cun cm ln lt l50 V, 90 V, 40 V. iu chnh gi trbin trln gp i so vi lc u th in p hiu dng trn bintrl

A.50 2 V B.100 V C.25 V D.20 10 VCu 7. t mt in p xoay chiu vo hai u on mch gm in trthun R, cun cm thun L vtin C c in dung thay i. Khi C=C1th in p hiu dng trn cc phn tln lt l UR=40 V,

UL=40 V, UC=70 V. Khi C=C2, in p hiu dng hai u tl 50 2 V. in p hai u in trkhi l

A.25 2 V B.25 V C. 25 3 V D.50 VCu 8. on mch xoay chiu ni tip gm in trthun R, tin C v cun cm thun L. t vo

hai u on mch mt in p xoay chiu n nh th in p hiu dng trn R, L, v C ln lt l 30 V,100 V v 60 V. Thay L bi cun cm L th in p hiu dng trn cun cm l 50 V. in p hiu dngtrn R khi l


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A.150 V B.80 V C.40 V D. 20

2 VCu 9. on mch xoay chiu ni tip gm in trthun R, tin C v cun cm thun L. t vohai u on mch mt in p xoay chiu n nh th in p hiu dng trn R, L, v C ln lt l 40 V,50 V v 120 V. Thay R bi in tr 2,5R R th cng hiu dng trong mch l 3,4 A.Dung khngca tbngA.23,3 B.25 C.19,4 D.20

Cu 10. on mch xoay chiu ni tip gm bin trR, tin C v cun cm thun L. t vo hai uon mch mt in p xoay chiu n nh th in p hiu dng trn R, L, v C ln lt l 10 3 V, 40V v 30 V. iu chnh bin trin p hiu dng hai u bin trl 10 V th in p hiu dng haiu cun thun cm v hai u tin ln lt lA.69,2 V v 51,9 V B.58,7 V v 34,6 V C.78,3 V v 32,4 V D.45,8 V v 67,1 VCu 11. on mch xoay chiu ni tip gm in trthun R v tin C.t vo hai u on mchmt in p xoay chiu n nh th in p hiu dng trn R v C ln lt l 60 V v 80 V. Sau khi tin bnh thng th in p hiu dng trn R lA.20 V B.60 V C.100 V D.140 V

Cu 12.(H 2012). t in p 400cos100u t (u tnh bng V, t tnh bng s) vo hai u on mch

AB gm in trthun 50 mc ni tip vi on mch X. Cng dng in hiu dng qua mch l2A.Bit thi im t, in p tc thi gia hai u AB c gi tr400V; thi im

1

400t s , cng

dng in tc thi qua on mch bng khng v ang gim. Cng sut tiu thin ca on mch X lA.400 W B.200W C.160 W D.100 W

Cu 13.t in p 400cos100u t (u tnh bng V, t tnh bng s) vo hai u on mch AB gmin trthun 50 mc ni tip vi on mch X. Cng dng in hiu dng qua mch l 2A.Bit

thi im t, in p tc thi gia hai u AB c gi tr400V; thi im1

400t s , cng dng in

tc thi qua on mch bng 2A v ang gim. Cng sut tiu thin ca on mch AB l

A.400 W B.200W C. 400 2 W D.100 WCu 14.t in p 400cos100u t (u tnh bng V, t tnh bng s) vo hai u on mch AB gmin trthun 50 mc ni tip vi on mch X. Cng dng in hiu dng qua mch l 2A.Bit

thi im t, in p tc thi gia hai u AB c gi tr400V; thi im1

400t s , cng dng in

tc thi qua on mch bng khng v ang gim. Cng sut tiu thin ca on mch AB lA.400 W B.200W C.160 W D.100 W

Cu 15. t in p 400cos100u t (u tnh bng V, t tnh bng s) vo hai u on mch ABgm in trthun 50 mc ni tip vi on mch X. Cng dng in hiu dng qua mch l 2A.

Bit thi im t, in p tc thi gia hai u AB c gi tr200 2 V ; thi im1

400t s , cng

dng in tc thi qua on mch bng 2A v ang gim. Cng sut tiu thin ca on mch X lA.400 W B.300W C.200 W D.100 W

2. VIT BIU THC HIU IN THV CNG DNG INCu 16. Mt on mch xoay chiu ni tip AB gm in tr100, cun cm thun c cm khng100 v tin c dung khng 200. Bit in p tc thi gia hai u cun cm c biu thc

100cos 100 (V)6L

u t

. Biu thc in p hai u on mch AB l

A.11

100 2 cos 100 (V)12

u t

B.11

100 2 cos 100 (V)12

u t

C. 50cos 100 (V)12u t

D. 50 2 cos 100 (V)12u t


37/130



Cu 17. Mt on mch xoay chiu gm cun dy khng thun cm c in tr 25 3R vcmkhng 75mc ni tip vi tin C c dung khng 100. Bit in p tc thi gia hai u cun cm

c biu thc 90cos 100 (V)6RL

u t

. Biu thc in p hai u on mch l

A. 30 3 cos 100 (V)

3

u t

B. 30 2 cos 100 (V)

3

u t

C. 30 3 cos 100 (V)6

u t

D. 30 2 cos 100 (V)6

u t

Cu 18. (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 c0,1

L H

, tin c0,5

C mF

v in p gia hai u cun cm thun

l 20 2 cos 100 (V)2L

u t

. Biu thc in p gia hai u on mch l

A. 40cos 100 (V)

4

u t

B. 40cos 100 (V)

4

u t

C. 40 2 cos 100 (V)4

u t

D. 40 2 cos 100 (V)4

u t

Cu 19. on mch xoay chiu khng phn nhnh gm cc phn ttheo ng tht: in trthun

30, cun dy thun cm c tcm0,6

L H

v tin c in dung100

C F

. in p trn

on mch chgm cun cm v tin c biu thc: 160cos 100 (V)3LC

u t

. Biu thc dng

in qua mch l

A. 4 2 cos 100 (A)6u t

B. 4cos 100 (A)3u t

C. 4cos 100 (A)6

u t

D. 4cos 100 (A)6

u t

Cu 20. (H 2010). t in p 0 cosu U t vo hai u on mch gm in trthun R, cun cm

thun c tcm L v tin c in dung C mc ni tip. Gi I l cng dng in tc thi trongon mch, u1, u2v u3ln lt l in p tc thi gia hai u in tr, gia hai u cun cm v giahai u tin. Hthc ng l

A.2

2 1

ui

R L c

B. 3i u C

C. 1u

iR

D. 2u

iL

Cu 21. on mch gm cun dy c in trthun 100 3 , c tcm L ni tip vi tin c

in dung50

C F

. t vo hai u on mch mt in p xoay chiu 0 cos 100 (V)4u U t

th biu thc cng dng in tc thi qua mch: 2 cos 100 (A)12

i t

. Xc nh L.

A.

0,4L H B.

0,6L H C.

1L H D.

0,5L H


38/130



Cu 22. t in p xoay chiu

2 cos 100 (V)u U t vo hai u on mch ni tip gm in tr

R=50, cun cm thun L v tin C th dng in qua mch c biu thc

2 2 cos 100 (A)4

i t

. Gi ULv UCln lt l in p hiu dng trn L v trn C.Hthc

ng l

A. 100 VL CU U B. 100 VC LU U C. 50 2 VL CU U D. 100 2 VC LU U

Cu 23. t in p xoay chiu 0 cos (V)4u U t

vo hai u on mch ni tip gm in tr

R=50, cun cm thun L v tin C th dng in qua mch c biu thc 2 2 cos 100 (A)i t .

Gi ULv UCln lt l in p hiu dng trn L v trn C.Hthc ng lA. 100 VL CU U B. 100 VC LU U

C. 50 2 VL CU U D. 100 2 VC LU U

Cu 24. t in p xoay chiu 0 cos (V)4u U t vo hai u on mch ni tip gm in tr

R=50 v cun cm thun L th dng in qua mch c biu thc 05

sin 100 (A)12

i I t

. Ts

in trthun R v cm khng ca cun cm l

A.1

3 B.1 C. 0,5 3 D. 3

Gii bi ton hp kn bng phng php tng trphcCu 25. Mt on mch xoay chiu gm in trthun R mc ni tip vi hp kn X. Bit hp kn X chcha mt trong ba phn t: in trthun R1hoc cun dy thun cm L hoc tin C.Biu thc in

p hai u on mch v cng dng in trong mch ln lt l: 100 2 cos100 (V)u t v

4cos 100 (A)4

i t

. Hp kn X l

A.in trthun 50 B.cm thun vi cm khng ZL=25C.tin vi dung khng ZC=50 D.cm thun vi cm khng ZL=50Cu 26. Mt on mch cha hai trong ba phn t: tin, in trthun, cun cm thun mc ni tip.Bit biu thc in p hai u on mch v cng dng in trong mch ln lt l:

60cos 100 (V)2

u t

v 2sin 100 (A)6

i t

. on mch cha

A. 15 3 ; Z 15LR B. 15 ; Z 15 3CR C. 15 3 ; Z 15CR D. 15 ; Z 15 3LR

Cu 27. in p hai u cun dy c dng u=100cos100t (V) v cng dng in qua mch c

dng 2cos 100 (A)3

i t

. in trthun ca cun dy l

A. 25 2 B.25 C.50 D.125 Cu 28. Mt on mch AB gm in trR mc ni tip vi cun dy. Bit in p gia hai u in

trv hai u cun dy ln lt l 120cos100 (V)Ru t v 120cos 100 (V)3cdu t

. Kt

lun no khng ng?A.cun dy c in trr khc 0.


39/130



B.in p hai u on mch AB trpha6

so vi in p hai u cun dy.

C.in p hiu dng gia hai u on mch AB l 60 3 (V) .

D.Hscng sut ca on mch AB bng 0,5 3 .Cu 29. on mch AB gm hai on mch AM v MB mc ni tip. on AM gm in trthun 50

mc ni tip vi tin c dung khng 50 . Bit biu thc in p trn on AM v trn on MBln lt l: 80cos 100 (V)

4AMu t

v 200 2 cos 100 (V)

4MBu t

. Tnh tng trca

on MB v lch pha ca in p trn MB so vi dng in.

A. 250 ;4

B.250 ; -

4

C.125 2 ; -

2

D.125 2 ;

2

Cu 30. (H 2011). on mch AB gm hai on mch AM v MB mc ni tip. on mch AM gm

in trthun R1=40 mc ni tip vi tin c in dung0,25

C mF

, on mch MB gm in

trthun R2mc ni tip vi cun cm thun. t vo A, B in p xoay chiu c gi trhiu dng v tn

skhng i th in p tc thi hai u on mch AM v MB ln lt l:750 2 cos 100 (V)

12AMu t

v 150cos 100 (V)MBu t . Hscng sut ca on mch AB

lA.0,86 B.0,84 C.0,95 D.0,71

Cu 31. Cun dy thun cm c hstcm2

(H)L

mc ni tip vi on mch X. t vo hai

u mch mt in p 120 2 cos 100 (V)MBu t th cng dng in qua cun dy l

0,6 2 cos 100 (A)6

i t

. Tm hiu in thhiu dng hai u on mch X.

A.240 V B.120 3 V C.60 2 V D.120 V3. HIN TNG CNG HNG. BI TON Z1=Z2Cu 32. Mt mch in xoay chiu gm mt tin C mc ni tip vi mt cun dy. t vo hai u

on mch mt in p 2cosu U t th in p hai u tin C l 2cos3C

u U t

. Ts

gia dung khng v cm khng bng

A.1

3 B.

1

2 C.1 D.2

Cu 33. t in p xoay chiu 0 cosu U t vo hai u on mch ni tip gm in trthun R,

cun cm thun c tcm L v tin c in dung thay i C.Khi in cung ca tl C th in

p hai u cun thun cm l 0 2cos 3Lu U t

. Mun mch xy ra cng hng th phi thay i

in dung ca tin n gi trbng

A. 2C B.0,65C C.0,5C D.2CCu 34. Mt on mch ni tip gm cun cm thun, tin v in trR. t vo hai u on mchin p xoay chiu c gi trhiu dng 120 V th cm khng cun cm l 25 v dung khng ca tl100 . Nu tng tn sdng in ln hai ln th in p hiu dng hai u in trR lA.0 B.120 V C.240 V D.60 V

Cu 35. Mt on mch ni tip gm cun cm thun, tin v in trR. t vo hai u on mch

in p xoay chiu c gi trhiu dng U th dung khng gp bn ln cm khng. Nu tng tn scadng in k ln th in phai u in trR l U. Gi trk bngA.0,5 B.2 C.4 D.0,25


40/130



Cu 36. Mt on mch AB mc ni tip gm in trthun R, tin c in dung C v cun cmthun c tcm L thay i C.t vo hai u on mch AB in p xoay chiu 100 V50 Hz.

iu chnh L 2 6,25L

RC

v in p hai u cun cm lch pha so vi in p hai u on

mch AB gc2

. in p hiu dng hai u cun cm l

A.20 V B.30 V C.40 V D.50 VCu 37. Mch gm cun cm v tin c in dung thay i c mc ni tip ri mc vo ngun

xoay chiu 100 2cosu t , khng i. iu chnh in dung mch cng hng, lc ny hiuin thhiu dng hai u cun cm bng 200 V. Khi hiu in thhiu dng gia hai bn tl

A.100 3 V B.200 V C.100 V D.100 2 VCu 38. on mch xoay chiu ni tip AB gm in trthun R, tin C v cun cm L,r. Gi M lim gia in trR v tin, N l im gia tin v cun dy. t vo hai u on mch mt inp xoay chiu 120 V50 Hz th in p gia hai u on AN v in p gia hai u on MB ubng 90 V v trong mch ang c cng hng in. in p hiu dng gia hai u tin l

A. 30 2 V B. 60 2 V C. 30 3 V D. 30 V

Cu 39. t in p xoay chiu 220cos100 (V)u t vo hai u on mch gm in trthun

100, cun dy thun cm c tcm1

(H)

v tin c in dung C thay i mc ni tip. Nu

thay i in dung C t200

F

n50

F

th cng dng in hiu dng qua mch

A.gim. B.tng. C.cc i ti 2C C . D.tng ri gim.

Cu 40. Mch xoay chiu gm R1, L1, C1mc ni tip c tn scng hng l f1. Mch R2, L2, C2mcni tip c tn scng hng l f2. Bit C1=2C2v f2=2f1. Mc ni tip hai mch ny vi nhau th tn scng hng l

A.1

2f B.1

f C.1

2f D.1

3f

Cu 41. Hai mch in xoay chiu ni tip gm R1, L1, C1v R2, L2, C2u c tn scng hng l f.Mc ni tip hai mch ny vi nhau th tn scng hng lA.f B.1,5f C.2f D.3f

Cu 42. on mch xoay chiu nh hnh v. tvo hai u A,B hiu in thxoay chiu c gi trhiu dng khng i v tn s50 Hz. Bit tin

c in dung410

(F)

. Khi kha K chuyn tv

tr (1) sang (2) th schca ampe kkhng i. tcm ca cun dy l

A.

210

(H)

B.

110

(H)

C.

1

(H) D.10

(H) Cu 43. Mt on mch xoay chiu gm in trthun R, cun dy thun cm c tcm L v tin c in dung thay i c mc ni tip. t vo hai u on mch hiu in th

100 2 cos100 (V)u t . Khi thay i in dung C, ngi ta thy c hai gi trca C l410

(F)

v

410(F)

3

th cng dng in qua mch u c gi trhiu dng 0,7071 A.Gi trca R v L bng

A.1

H; R=100L

B.2

H; R=100 3L

C.

2H; R=100L D.

1H; R=100 3L

L

CRA

A B

1

2


41/130



Cu 44. t hiu in th 200cos100 (V)u t vo hai u on mch RLC mc ni tip c C thay

i C.Khi thay i in dung C, ngi ta thy ng vi hai gi trC1=31,8 F v C2=10,6 F th dngin trong mch u l 1 A.Biu thc dng in khi C=31,8 F l

A. 2cos 100 (A)6

i t

B. 2cos 100 (A)6

i t

C. 2 cos 100 (A)4i t

D. 2 cos 100 (A)6i t

4. LCH PHACu 45. Cho on mch xoay chiu mc ni tip theo ng thtgm cun cm thun c tcm

4(H)L

, in trthun R v tin c in dung

0,1(mF)C

. Nu in p hai u on cha RL

vung pha vi in p hai u on cha RC th R bngA.30 B.200 C.300 D.120Cu 46. Mt on mch in xoay chiu gm cun dy c in tr100 mc ni tip vi tin cdung khng 200 . Nu lch pha ca in p gia hai u cun dy v in p hai u on mch l5

12

th cm khng ca cun dy bng

A. 100 2 3 hoc 100 3 B.100

C.100 3 D.300 hoc 100 3

Cu 47. Sdng mt in p xoay chiu n nh v ba linh kin gm in trR, tin C v cun cmthun L. Khi mc ln lt hai on mch ni tip RC hoc RL vo in p ni trn th cng dng

in tc thi trong hai trng hp lch pha nhau2

3

v c cng gi trhiu dng 2A.Khi mc on

mch ni tip RLC vo in p ni trn th gi trcng dng in hiu dng trong mch lA.1A B.2A C.3A D.4A

Cu 48. t in p xoay chiu c tn sgc thay i c vo hai u on mch gm cun thuncm L v in trthun R mc ni tip. Khi = 1v =2th lch pha ca hiu in thhai u

on mch so vi cng dng in ln lt l 1v 2. Bit 1 2 4

. Chn hthc ng

A. 2 21 2 1 2RL R L B. 2 2

1 2 1 2RL R L

C. 2 21 2 1 22RL R L D. 2 2

1 2 1 22RL R L

Cu 49. t mt in p xoay chiu n nh vo hai u on mch gm in trthun R, cun dy

thun cm L v tin C mc ni tip th cng dng in trong mch sm pha3

so vi hiu in

thhai u on mch v c gi trhiu dng I. Sau , ngi ta tng gi trR v L ln hai ln v gim C

i hai ln. Chn pht biu ng vcng dng in trong machA.I khng i, lch pha khng i B.I gim 2 ln, lch pha khng iC.I gim 2 ln, lch pha khng i D.I v lch pha u gim

Cu 50. t mt in p xoay chiu 100 5 cos100 (V)u t vo hai u on mch ni tip gm

in trthun R, cun cm thun c tcm L thay i c v tin c dung khng ZC=3R. KhiL=L0th dng in c gi trhiu dng I v sm pha hn in p hai u on mch. Khi L=2L0th dngin c gi trhiu dng 0,5I v trpha hn in p hai u on mch mt gc 2>0. Xc nh tan2.A.tan2=0,5 B.tan2=1 C.tan2=1,5 D.tan2=2P N

1D 2C 3B 4B 5B 6D 7A 8C 9A 10A 11C 12B 13C 14A 15C 16A 17A 18B 19D 20C

21C 22C 23A 24A 25B 26B 27B 28C 29A 30B 31D 32D 33B 34B 35B 36C 37A 38B 39D 40A

41A 42C 43C 44C 45B 46A 47D 48A 49C 50D


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BI TP TNG HPCu 1. Trong mch RLC mc ni tip, lch pha gia dng in v hiu in thhai u on mchphthucA.cng dng in hiu dng trong mch B.hiu in thhiu dng gia hai u on mchC.cch chn gc thi gian D.tnh cht ca mch in.Cu 2. Trong mch xoay chiu ni tip th dng in nhanh hay chm pha so vi hiu in thhai uca on mch l ty thuc:A.R v C B.L v C C.L,C v D.R,L,C v Cu 3. Trong mch in xoay chiu gm R, L, C mc ni tip th

A.lch pha ca uLv u l2

B.uLnhanh pha hn uRgc2

C.uCnhanh pha hn i gc2

D.uLchn pha hn igc2

Cu 4. Mt on mch in xoay chiu gm R, L, C mc ni tip th

A.lch pha ca i v u l2

B.uLsm pha hn u gc2

C.uCtrpha hn uRgc 2

D.uCtrpha hn u gc 2

Cu 5. Mch RLC mc ni tip, lch pha gia hiu in thhai u on mch v cng dng

in trong mch l u i4

th

A.mch c tnh dung khng. B.mch c tnh cm khng.C.mch chc in trthun. D.mch cng hng in.Cu 6. Hscng sut cosca on mch xoay chiu RLC mc ni tip bng 0 khi

A. 1

LC

. B.P=Pmax. C.R=0. D.U=UR.

Cu 7. Chn pht biu khng ng. Trong mch in xoay chiu khng phn nhnh, khi in dung ca

tin thay i v tha mn iu kin 1LC

th

A.cng dng in tc thi qua mch cng pha vi hiu in thhiu dng gia hai u on mch.B.cng dng in hiu dng trong mch t cc i.C.cng sut tiu thtrung bnh trong mch t cc i.D.hiu in thhiu dng gia hai u in trt cc i.Cu 8. Chn pht biu khng ng. Trong mch in xoay chiu khng phn nhnh, khi in dung ca

tin thay i v tha mn iu kin1

LC

th

A.hiu in thhiu dng gia hai u cun cm t cc i.B.hiu in thhiu dng gia hai u cun cm v tin bng nhau.C.tng trca mch t gi trln nht.D.hiu in thhiu dng gia hai u in trt cc i.Cu 9. Trong on mch RLC ni tip ang xy ra hin tng cng hng. Tng dn tn sca dngin v ginguyn cc thng sca mch. Kt lun no sau y l khng ng:A.Hscng sut ca on mch gim. B.Cng hiu dng ca on mch gim.C.Hiu in thhiu dng trn tin tng. D.Hiu in thhiu dng trn in trgim.Cu 10. Pht biu no sau y l khng ng? Trong mch in xoay chiu khng phn nhnh ta c thto ra hiu in thhiu dng gia hai uA.cun cm ln hn gia hai u on mch. B.tin ln hn gia hai u on mch.C.in trln hn gia hai u on mch. D.tin v gia hai u cun cm bng nhau.Cu 11. Chn pht biu ngA.Dng in xoay chiu c thdng min.B.Mch RLC c tng trcc tiu khi 2 24 f LC 1


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C.Si dy st cng ngang trn li st ca ng dy c dng in xoay chiu chy qua sdao ng cngbc vi tn sdao ng bng tn sca dng in.D.Nhit lng ta ra in trR khi c dng in xoay chiu cng cc i I0qua l 20Q RI t .

Cu 12. Dung khng ca mt mch RLC mc ni tip ang c gi trnhhn cm khng. Mun xy rahin tng cng hng in trong mch ta phiA.tng in dung ca tin. B.tng hstcm ca cun dy.

C.gim in trca mch. D.gim tn sdng in xoay chiu.Cu 13. Khi hiu in thgia hai u on mch RLC mc ni tip sm pha

4i vi dng in

trong mch thA.tn sca dng in trong mch nhhn gi trtn skhi xy ra hin tng cng hng.B.tng trca mch gp i in trthun.C.hiu sgia cm khng v dung khng bng in trthun ca mch.

D.hiu in thgia hai u in trsm pha

4so vi hiu in thgia hai u tin.

Cu 14. t in p xoay chiu c tn sf=50 Hz vo hai u mt mch in gm in trthun

R=60, cun cm thun c tcm 0,4

L H v tin c in dung

410

C F

mc ni tip.

Tng trca mch v lch pha gia in p v cng dng in trong mch ln lt l

A. 60 ; rad4

B. 60 2 ; rad

4

C. 60 2 ; - rad

4

D. 60 ; - rad

4

Cu 15. t in p xoay chiu c tn sf=50 Hz vo hai u mt mch in gm in trthun


L H

v tin c in dung 100

C F

mc ni tip.

Tng trca mch lA. 50 B. 40 C. 60 D. 45

Cu 16. t in p xoay chiu u 100 2 cos100 t V vo hai u mt mch in gm in trthun


L H

v tin c in dung 310

C F8

mc ni tip.

lch pha gia dng in qua mch v in p u l

A. rad4

B. rad

4

C. rad

6

D. - rad

6

Cu 17. t in p xoay chiu c tn sf=50 Hz vo hai u mt mch in gm in trthunR=30v mt tin mc ni tip. Bit cc in p hiu dng gia hai u in trv hai u tinln lt l 90 V v 150 V. in dung ca tin l

A.50 F B.50.10-3F C. 310

F5

D.

310F

2

Cu 18. t in p xoay chiu vo hai u mt mch in gm in trthun R=30, cun cm thun

c cm khng ZL=70v tin mc ni tip. Bit cng dng in qua mch trpha3

so vi in

p hai u on mch. Tng trcu mch v dung khng ca tin ln lt lA. 60 ; 18 B. 60 ; 12 C. 50 ; 15 D. 70 ; 28

Cu 19. t in p xoay chiu u 200cos100 t V vo hai u mt on mch ni tip gm in tr

thun R, cun cm thun c tcm L v tin c in dung C thay i C.Khi thay i indung C ca t, th ng vi hai gi trC=C1=31,8 F v C=C2=10,6 F, cng dng in trong mchu c gi trhiu dng 1A.Tnh tcm ca cun dy v in trca mch

A. 1

R 100 ; L= H

B.2

R 100 3 ; L= H

C.2

R 100 ; L= H

D.1

R 100 3 ; L= H

Cu 20. t in p xoay chiu u 200cos100 t V vo hai u mt on mch ni tip gm in tr

thun R, cun cm thun c tcm L=0,318H v tin c in dung C thay i C.Khi thay i


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in dung C ca t, th ng vi gi trC=63,6 F, dng in qua mch lch pha4

so vi hiu in th

hai u on mch. in trca mch lA. R 40 B. R 60 C. R 50 D. R 100 Cu 21. Mt cun dy c in trthun 40, lch pha gia in p hai u cun dy v dng inqua cun dy l 450. Cm khng v tng trca cun dy ln lt l

A. 50 ; 50

2 B. 30 ; 50 C. 40 ; 40 2 D. 30 ; 30 2 Cu 22. t in p xoay chiu c tn sf thay i c vo hai u mt mch in gm in trthun

R, cun cm thun c tcm 1

L H

v tin c in dung 410

C F

mc ni tip. Thay i

tn sf cng dng in hiu dng qua mch t gi trcc i, tn sf khi lA.100 Hz B.60 Hz C.50 Hz D.120 Hz

Cu 23. t in p xoay chiu c gi trhiu dng 50 V v tn sf=50 Hz vo hai u mt mch in

gm in trthun R=40, cun cm thun c tcm L v tin c in

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