CHUYÊN ĐỀ 2 - DÒNG ĐIỆN KHÔNG ĐỔI

7/29/2019 CHUYN 2 - DNG IN KHNG I

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H V TN:...............................TRNG:.......

I. Kin thc:

1. Cng dng in c xc nh bng thng s ca in lng q dch chuyn quatit din thng ca vt dn trong khong thi gian t v khong thi gian . I =

t

q

2. Dng in khng i l dng in c chiu v cng khng thay i theo thi giann v ca cng dng in l Ampe (A).

3. Ngun in l mt ngun nng lng c kh nng cung cp in nng cho cc dng ctiu th in mch ngoi.

Sut in ng ca ngun in l i lng c trng cho kh nng thc hin cng cangun in v c o bng thng s gia cng A ca lc l thc hin khi dch chuyn mt intch dng q ngc chiu in trng (trong vng c lc l) v ln ca in tch .

n v ca sut in ng l Vn (V)4. Cu to ca pin, acquy. Nguyn tc hot ng ca pin, acquy.

Pin in ha gm 2 cc c bn cht ha hc khc nhau c ngm trong cht in phn(dd axit, baz, hoc mui,) Do tc dng ha hc, cc cc ca pin in ha c tch in khcnhau v gia chng c mt hiu in th bng gi tr sut in ng ca pin.

Acquy l ngun in ha hc hot ng da trn phn ng ha hc thun nghch, n tchtr nng lng lc np in v gii phng nng lng ny khi pht in.

5. i vi mt dy dn c in tr R, ta c nh lut m : IRU

= , vi U l hiu in th gia

hai u dy, I l cng dng in chy qua dy.III. Bi tp:

Hng dn gii bi tp:- ch ny, cc cu hi v bi tp ch yu l v: c im dng in khng i v cng

thc I =t

q , nh ngha sut in ng v cng thcq

A= , cu to chung ca cc ngun in ha

hc.- Cn lu nhng vn sau:

+ n v ca cc i lng: Trong cng thc I =t

q n v ca I l Ampe (A) ca q l

Culng (C), ca t l giy (s) v vy nu bi cho thi gian l pht, gi, th phi i ra giy.+ Cn ch s khc bit gia lc lm di chuyn in tch mch ngoi v mch trong

(bn trong ngun in).+ Bn trong cc ngun in ha hc c s chuyn ha t ha nng thnh in nng.

+ Dng in khng i c c chiu v cng khng thay i theo thi gian, v vy chiudch chuyn c hng ca cc in tch l khng i v in lng dch chuyn qua tit din thngca vt dn s t l thun vi thi gian.

Dng 1: CNG DNG IN, SUT IN NG CA NGUN IN.PP chung: Tnh cng dng in, s electron i qua mt on mch.

Dng cc cng thc I = t

q

R

U

= (q l in lng dch chuyn qua on mch)

I CNG DNG IN KHNG I- NGUN IN.


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N =e

q ( e = 1,6. 10-19 C)

Tnh sut in ng hoc in nng tch ly ca ngun in.

Dng cng thcq

A= ( l sut in ng ca ngun in, n v l Vn (V) )

1. Cng dng in chy qua dy tc bng n l I = 0,5 A.a. Tnh in lng dch chuyn qua tit din thng ca dy tc trong 10 pht ?b. Tnh s electron dch chuyn qua tit din thng ca dy tc trong khong thi gian trn ?

s: 300 C, 18,75. 1020 ht e.2. Sut in ng ca mt ngun in l 12 V. Tnh cng ca lc l khi dch chuyn mt lngin tch l 0,5 C bn trong ngun in t cc m n cc dng ca n ?

s: 6 J.3. Tnh sut in ng ca ngun in. Bit rng khi dch chuyn mt lng in tch 3. 10-3 Cgia hai cc bn trong ngun in th lc l thc hin mt cng l 9 mJ.

s: 3 V.4. Sut in ng ca mt acquy l 6 V. Tnh cng ca lc l khi dch chuyn mt lng in tchl 0,16 C bn trong acquy t cc m n cc dng ca n ?

s: 0,96 J.5. Tnh in lng v s electron dch chuyn qua tit din ngang ca mt dy dn trong mt pht.

Bit dng in c cng l 0,2 A. s: 12 C, 0,75. 1020 ht e.

6. Mt b pin ca mt thit b in c th cung cp mt dng in 2 A lin tc trong 1 gi th phinp li.

a. Nu b pin trn c s dng lin tc trong 4 gi ch tit kim nng lng th phinp li. Tnh cng dng in m b pin ny c th cung cp?

b. Tnh sut in ng ca b pin ny nu trong thi gian 1 gi n sinh ra mt cng l 72 KJ. s: 0,5 A, 10 V.

7. Trong 5 giy lng in tch dch chuyn qua tit din thng ca mt dy dn l 4,5 C. Cng dng in chy qua dy dn l bao nhiu ?

s: 0,9 A.II.BI TP TRC NGHIM.

Cu hi 1: Dng in l:A. dng dch chuyn ca in tchB. dng dch chuyn c hng ca cc in tch t doC. dng dch chuyn c hng ca cc in tch t doD. dng dch chuyn c hng ca cc ion dng v m

Cu hi 2: Quy c chiu dng in l:A.Chiu dch chuyn ca cc electronB. chiu dch chuyn ca cc ion

C. chiu dch chuyn ca cc ion mD. chiu dch chuyn ca cc in tch dng

Cu hi 3: Tc dng c trng nht ca dng in l:A.Tc dng nhit B. Tc dng ha hc C. Tc dng t D. Tc

dng c hcCu hi 4: Dng in khng i l:

A. Dng in c chiu khng thay i theo thi gianB. Dng in c cng khng thay i theo thi gianC. Dng in c in lng chuyn qua tit din thng ca dy khng i theo thi gianD. Dng in c chiu v cng khng thay i theo thi gian


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Cu hi 5: Sut in ng ca ngun in nh ngha l i lng o bng:A. cng ca lc l tc dng ln in tch q dngB. thng s gia cng v lc l tc dng ln in tch q dngC. thng s ca lc l tc dng ln in tch q dng v ln in tch yD. thng s cng ca lc l dch chuyn in tch q dng trong ngun t cc m n ccdng vi in tch

Cu hi 6: Tnh s electron i qua tit din thng ca mt dy dn kim loi trong 1 giy nu cin lng 15C dch chuyn qua tit din trong 30 giy:

A. 5.106 B. 31.1017 C. 85.1010 D. 23.1016

Cu hi 7: S electron i qua tit din thng ca mt dy dn kim loi trong 1 giy l 1,25.1019.Tnh in lng i qua tit din trong 15 giy:

A. 10C B. 20C C. 30C D. 40CCu hi 8: Hai in tr mc song song vo ngun in nu R1< R2 v R12 l in tr tng ngca h mc song song th:A. R12 nh hn c R1v R2.Cng sut tiu th trn R2 nh hn trn R1.

B.R12 nh hn c R1v R2.Cng sut tiu th trn R2 ln hn trn R1.C. R12 ln hn c R1 v R2. D. R12 bng trung bnh nhn ca R1 v R2

Cu hi 9: Ba in tr bng nhau R1 = R2 = R3 mc nh hnh v. Cngsut tiu th:

A. ln nht R1 B. nh nht R1

C. bng nhau R1 v h ni tip R23 D. bng nhau R1, R2 ,R3

Cu hi 10: Hai bng n c hiu in th nh mc ln lt l U1 = 110V, U2 = 220V. Chng ccng sut nh mc bng nhau, t s in tr ca chng bng:

A. B. C. D.

Cu hi 11: bng n 120V 60W sng bnh thng mng inc hiu in th 220V ngi ta mc ni tip n vi in tr ph R. R cgi tr:

A. 120 B. 180 C. 200 D. 240Cu hi 12: Ba in tr bng nhau R1 = R2 = R3 ni vo ngun nh hnhv. Cng sut tiu th :

A. ln nht R1 B. nhnht R1

C. bng nhau R1 v b hai in tr mc song song D. bngnhau R1, R2 v R3

Cu hi 13: Khi hai in tr ging nhau mc song song v mc vo ngun in th cng sut tiuth l 40W. Nu hai in tr ny mc ni tip vo ngun th cng sut tiu th l:

A. 10W B. 80W C. 20W D. 160WCu hi 14: Mc hai in tr R1 = 10 , R2 = 20 vo ngun c hiu in th U khng i. Sosnh cng sut tiu th trn cc in tr ny khi chng mc ni tip v mc song song thy:

A. ni tip P1/P2 = 0,5; song song P1/P2 = 2 B. ni tip P1/P2 = 1,5; song song P1/P2 =0,75C. ni tip P1/P2 = 2; song song P1/P2 = 0,5 D. ni tip P1/P2 = 1; song song P1/P2 = 2

Cu hi 15: Mt bp in gm hai dy in tr R1 v R2. Nu ch dng R1 th thi gian un sinc l 10 pht, nu ch dng R2 th thi gian un si nc l 20 pht. Hi khi dng R1 ni tip R2th thi gian un si nc l bao nhiu:

A. 15 pht B. 20 pht C. 30 pht D. 10pht

U

R2 R3

R1

U

R2

R3R1


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Cu hi 16: Mt bp in gm hai dy in tr R1 v R2. Nu ch dng R1 th thi gian un sinc l 15 pht, nu ch dng R2 th thi gian un si nc l 30 pht. Hi khi dng R1 song songR2 th thi gian un si nc l bao nhiu:

A. 15 pht B. 22,5 pht C. 30 pht D. 10phtCu hi 17: Mt bn l dng in 220V. C th thay i gi tr in tr ca cun dy trong bn lnh th no dng in 110V m cng sut khng thay i:

A. tng gp i B. tng 4 ln C. gim 2 ln D. gim4 lnCu hi 18: Hai bng n c cng sut nh mc l P1 = 25W, P2= 100W u lm vic bnhthng hiu in th 110V. So snh cng dng in qua mi bng v in tr ca chng:

A. I1.>I2; R1 > R2 B. I1.>I2; R1 < R2 C. I1. R2Cu hi 19: Hai bng n c cng sut nh mc l P1 = 25W, P2= 100W u lm vic bnhthng hiu in th 110V. Khi mc ni tip hai n ny vo hiu in th 220V th:

A. n 1 sng yu, n 2 qu sng d chy B. n 2 sng yu, n 1qu sngd chyC. c hai n sng yu D. c hai n sng bnh thng

Cu hi 20: Hai in tr ging nhau mc ni tip vo ngun in hiu in th U th tng cngsut tiu th ca chng l 20W. Nu chng mc song song vo ngun ny th tng cng sut tiuth ca chng l:

A. 5W B. 40W C. 10W D. 80W

Cu hi 21: Khi mt ti R ni vo ngun sut in ng v in tr trong r, thy cng sut mchngoi cc i th:A. = IR B. r =R C. PR= I D. I = /r

Cu hi 22: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Xc nh R cng sut ta nhit trn R cc i, tnh cng sut cc i :

A. R= 1, P = 16W B. R = 2, P = 18WC. R = 3, P = 17,3W D. R = 4, P = 21W

Cu hi 23: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Xc nh R bit R > 2, cng sut mch ngoi l 16W:

A. 3 B. 4 C. 5 D. 6

Cu hi 24: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Tnh cng dng in v hiu sut ngun in, bit R > 2, cng sut mchngoi l 16W:

A. I = 1A. H = 54% B. I = 1,2A, H = 76,6%C. I = 2A. H = 66,6% D. I = 2,5A. H = 56,6%

Cu hi 25: Khi dng in chy qua on mch ngoi ni gia hai cc ca ngun in th cc htmang in chuyn ng c hng di tc dng ca lc:

A. Cu long B. hp dn C. lc l D. in trngCu hi 26: Khi dng in chy qua ngun in th cc ht mang in chuyn ng c hng ditc dng ca lc:

A. Cu long B. hp dn C. lc l D. in trngCu hi 27: Cng dng in c biu thc nh ngha no sau y:

A. I = q.t B. I = q/t C. I = t/q D. I = q/eCu hi 28: Chn mt p n sai:

A. cng dng in o bng ampe kB. o cng dng in phi mc ni tip ampe k vi mchC. dng in qua ampe k i vo cht dng, i ra cht m ca ampe kD. dng in qua ampe k i vo cht m, i ra cht dng ca ampe k

Cu hi 29: n v ca cng dng in, sut in ng, in lng ln lt l:A. vn(V), ampe(A), ampe(A) B. ampe(A), vn(V), cu lng (C)


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C. Niutn(N), fara(F), vn(V) D. fara(F), vn/mt(V/m), jun(J)Cu hi 30: Mt ngun in c sut in ng l , cng ca ngun l A, q l ln in tch dchchuyn qua ngun. Mi lin h gia chng l:

A. A = q. B. q = A. C. = q.A D. A = q2.Cu hi 31: Trong thi gian 4s mt in lng 1,5C chuyn qua tit din thng ca dy tc bngn. Cng dng in qua bng n l:

A. 0,375A B. 2,66A C. 6A D. 3,75ACu hi 32: Dng in qua mt dy dn kim loi c cng 2A. S electron dch chuyn qua titdin thng ca dy dn ny trong 2s l:

A. 2,5.1018

B. 2,5.1019

C. 0,4. 1019

D. 4. 1019

Cu hi 33: Cng dng in chy qua tit din thng ca dy dn l 1,5A. Trong khong thigian 3s th in lng chuyn qua tit din dy l:

A. 0,5C B. 2C C. 4,5C D. 5,4CCu hi 34: S electron dch chuyn qua tit din thng ca dy trong thi gian 2s l 6,25.1018.Khi dng in qua dy dn c cng l:

A. 1A B. 2A C. 0,512.10-37 A D. 0,5ACu hi 35: Dng in chy qua bng n hnh ca mt ti vi thng dng c cng 60A. Selectron ti p vo mn hnh ca tivi trong mi giy l:

A. 3,75.1014 B. 7,35.1014 C. 2, 66.10-14 D.0,266.10-4Cu hi 36:Cng ca lc l lm di chuyn in tch 4C t cc m n cc dng bn trong ngunin l 24J. Sut in ng ca ngun l:

A. 0,166V B. 6V C. 96V D. 0,6VCu hi 37: Sut in ng ca mt cquy l 3V, lc l lm di chuyn in tch thc hin mtcng 6mJ. Lng in tch dch chuyn khi l:

A. 18.10-3 C. B. 2.10-3C C. 0,5.10-3C D. 1,8.10-3CCu hi 38: Cng dng in khng i chy qua on mch l I = 0,125A. Tnh in lngchuyn qua tit din thng ca mch trong 2 pht v s electron tng ng chuyn qua:

A. 15C; 0,938.1020 B. 30C; 0,938.1020 C. 15C; 18,76.1020 D.30C;18,76.1020

Cu hi 39: Pin in ha c hai cc l:A. hai vt dn cng cht B. hai vt cch inC. hai vt dn khc cht D. mt cc l vt dn, mt vt l in mi

Cu hi 40: Pin vnta c cu to gm:A. hai cc bng km(Zn) nhng trong dung dch axit sunphuric long(H2SO4)B. hai cc bng ng (Cu) nhng trong dung dch axit sunphuric long(H2SO4)C. mt cc bng km(Zn) mt cc bng ng (Cu) nhng trong dung dch axit sunphuriclong(H2SO4)D. mt cc bng km(Zn) mt cc bng ng (Cu) nhng trong dung dch mui

Cu hi 41: Hai cc ca pin Vnta tch in khc nhau l do:A. ion dng ca km i vo dung dch ca cht in phnB. ion dng H+ trong dung dch in phn ly electron ca cc ngC. cc electron ca ng di chuyn ti km qua dung dch in phnD. ion dng km i vo dung dch in phn v cc ion H+ ly electron ca cc ng

Cu hi 42: Acquy ch gm:A. Hai bn cc bng ch nhng vo dung dch in phn l bazB. Bn dng bng PbO2 v bn m bng Pb nhng trong dung dch cht in phn l axitsunfuric longC. Bn dng bng PbO2 v bn m bng Pb nhng trong dung dch cht in phn l baz


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D. Bn dng bng Pb v bn m bng PbO2 nhng trong dung dch cht in phn l axitsunfuric long

Cu hi 43: im khc nhau gia acquy ch v pin Vnta l:A. S dng dung dch in phn khc nhau B. s tch in khc nhau gia hai ccC. Cht dng lm hai cc ca chng khc nhau D. phn ng ha hc acquy c th syra thun nghch

Cu hi 44: Trong ngun in ha hc (Pin v acquy) c s chuyn ha nng lng t:A. c nng thnh in nng B. ni nng thnh in nngC. ha nng thnh in nng D. quang nng thnh in nng

Cu hi 45: Mt pin Vnta c sut in ng 1,1V. Khi c mt lng in tch 27C dch chuynbn trong gia hai cc ca pin th cng ca pin ny sn ra l:

A. 2,97J B. 29,7J C. 0,04J D. 24,54JCu hi 46: Mt b acquy c sut in ng 6V c dung lng l 15Ah. Acquy ny c th s dngthi gian bao lu cho ti khi phi np li, tnh in nng tng ng d tr trong acquy nu coi ncung cp dng in khng i 0,5A:

A. 30h; 324kJ B. 15h; 162kJ C. 60h; 648kJ D. 22h; 489kJCu hi 47: Mch in gm in tr R = 2 mc thnh mch in kn vi ngun = 3V, r = 1th cng sut tiu th mch ngoi R l:

A. 2W B. 3W C. 18W D. 4,5W

Cu hi 48: Mt ngun c = 3V, r = 1 ni vi in tr ngoi R = 1 thnh mch in kn.Cng sut ca ngun in l:A. 2,25W B. 3W C. 3,5W D. 4,5W

Cu hi 49: Mt mch in kn gm ngun in sut in ng = 6V, in tr trong r = 1 nivi mch ngoi l bin tr R, iu chnh R cng sut tiu th trn R t gi tr cc i. Cngsut l:

A. 36W B. 9W C. 18W D. 24WCu hi 50: Mt mch in kn gm ngun in sut in ng = 3V, in tr trong r = 1 nivi mch ngoi l bin tr R, iu chnh R cng sut tiu th trn R t gi tr cc i. Khi Rc gi tr l:

A. 1 B. 2 C. 3 D. 4

P NCu 1 2 3 4 5 6 7 8 9 10

pn

B D C D D B C A A C

Cu 11 12 13 14 15 16 17 18 19 20

pn

C A A B C D D D B D

Cu 21 22 23 24 25 26 27 28 29 30

pn

B B B C D C B D B A

Cu 31 32 33 34 35 36 37 38 39 40

pn

A B C D A B B A C C

Cu 41 42 43 44 45 46 47 48 49 50

pn

D B D C B A A D B A


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I. Kin thc:1. in nng tiu th ca mt on mch bng tch ca hiu in th gia hai u on mch vicng dng in v thi gian dng in chy qua on mch . A = U.I.t

2. Cng sut in ca mt on mch bng tch ca hiu in th gia hai u on mch v

cng dng in chy qua on mch . P =U.I=

t

A

3. Nu on mch l vt dn c in tr thun R th in nng tiu th ca on mch cbin i hon ton thnh nhit nng. Cng sut ta nhit ca vt dn khi c dng in chy qua

c xc nh bng nhit lng ta ra vt dn trong khong thi gian 1 giy. P = 22

R.I=R

U

4. Cng ca ngun in bng tch ca sut in ng ca ngun in vi cng dng inv thi gian dng in chy qua ngun in. Cng ca ngun in bng cng ca dng in chytrong ton mch. A = .I.t

5. Cng sut ca ngun in bng tch ca sut in ng ca ngun in vi cng dngin chy qua ngun in. Cng sut ca ngun in bng cng sut ca dng in chy trong ton

mch. P = .I=t

A

6. nh lut Jun_LenX: Nhit lng ta ra mt vt dn t l thun vi in tr ca vtdn, vi bnh phng cng dng in v vi thi gian dng in chy qua vt dn .

Q= R.I2.t7. Cng sut ca dng c tiu th in:

+ Vi dng c ta nhit: P = U.I = R.I2 =R

U2

+ Vi my thu in: P = .I + r.I2 = P + r.I2(Vi P = .I l phn cng sut m my thu in chuyn ha thnh dng nng lng c ch,

khng phi l nhit. V d: in nng chuyn ha thnh c nng )n v ca cng (in nng) v nhit lng l Jun (J); n v ca cng sut l ot (W)

III. Bi tp:Dng 1: VN DNG NH LUT JUN-LENX. CNG SUT IN.PP chung:Ap dng cng thc:

Cng v cng sut ca dng in on mch: A = U.I.t , P = U.I=t

A

nh lut Jun-LenX: Q = R.I

2

.t hay Q= U.I.t.

2

=tR

U

Cng sut ca dng c tiu th in: P = U.I = R.I2 =

R

U2

- ch ny, cc cu hi v bi tp ch yu v: Tnh in nng tiu th v cng sut in

ca mt on mch. Tnh cng sut ta nhit v nhit lng ta ra trn mt vt dn. Tnh cng v

cng sut ca ngun in.

- Cn lu nhng vn sau:+ Trong cc cng thc tnh cng, tnh nhit lng: c cng, nhit lng tnh ra c

n v l Jun (J) cn ch i n v thi gian ra giy (s).

12 Ch 2: IN NNG, NH LUT JUN-LENX ,CNG SUT IN.


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+ Mch in c bng n: R =dm

2

PdmU

( Coi nh in tr khng ph thuc vo hiu in th t vo n, khng thay i theo nhit .)Nu n sng bnh thng th Ithc = Im (Lc ny cng c Uthc = Um; Pthc = P m)Nu Ithc < Im th n m hn bnh thng.

Nu Ithc > Im th n sng hn bnh thng.R1 R2

1. Cho mch in nh hnh, trong U = 9V, R1 = 1,5 . Bit hiuin th hai u R2 = 6v. Tnh nhit lng ta ra trn R2 trong 2 pht ?

s: 1440 J.2. C hai in tr mc gia hai im c hiu in th 12 V.Khi R1 ni tip R2 th cng sut ca mch l 4 W. Khi R1 mc song song R2 th cng sut mch l18 W. Hy xc nh R1 v R2 ? s: R1 = 24 , R2 = 12 , hoc ngc li.3. Hai bng n 1 ghi 6v 3 W v 2 ghi 6V - 4,5 W cmc vo mch in nh hnh v. Ngun in c hiu in th U khng thay i. 2

a. Bit ban u bin tr Rb v tr sao cho 2 n sng Rbbnh thng. Tm in tr ca bin tr lc ny ? Trn mchin, u l 1, u l 2 ?

b. Gi s t v tr ban u ta di chuyn bin tr conchy sang phi mt cht th sng cc n thay i th no ? s: Rb = 24 4. Cho mch in thp sng n nh hnh, Ngun c sut in ng 12 V. n loi 6 V 3 W. iu chnh R n sng bnh thng. Tnh cng cangun in trong khong thi gian 1h ? Tnh hiu sut ca mch cha n

khi sng bnh thng ? s: 21600 J, 50 %.5. loi bng n loi 120 V 60 W sng bnh thng mng in c hiu n th 220V, ngita mc ni tip vi n mt in tr ph R. Tnh R ? s: 200

6. Cho mch in nh hnh vi U = 9V, R1 = 1,5 , R2 = 6 . R3Bit cng dng in qua R3 l 1 A. R1 R2a. Tm R3 ?

b. Tnh nhit lng ta ra trn R2 trong 2 pht ?c. Tnh cng sut ca on mch cha R1 ? s: 6 , 720 J, 6 W.

7. Mt qut in c s dng di hiu in th 220 V th dng in chy qua qut c cng l 5 A.

a. Tnh nhit lng m qut ta ra trong 30 pht theo n v Jun ?b. Tnh tin in phi tr cho vic s dng qut trong 30 ngy, mi ngy s dng 30 pht,

bit gi in l 600 ng / Kwh. (Bit 1 wh = 3600 J, 1 Kwh = 3600 KJ).

s: 1980000 J. (hay 0,55 kw). 9900 ng.

8. Mt m in c hai dy dn R1 v R2 un nc. Nu dng dy R1 th nc trong m s si saukhong thi gian 40 pht. Cn nu dng dy R2 th nc s si sau 60 pht. Vy nu dng c haidy mc song song th m nc s si sau khong thi gian l bao nhiu ? (Coi in tr ca dythay i khng ng k theo nhit .)

s: 24pht.


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9. Ba in tr ging nhau c mc nh hnh, nu cng sut tiu th trn in tr (1) l 3 W thcng sut ton mch l bao nhiu ?

s: 18 W.10. Ba in tr c tr s R, 2 R, 3 R mc nh hnh v. Nu cng sut ca in tr (1) l 8 W thcng sut ca in tr (3) l bao nhiu ?

s: 54W.

II. BI TP TRC NGHIM:Cu hi 1: Mt b acquy c sut in ng 6V c dung lng l 15Ah. Acquy ny c th s dngthi gian bao lu cho ti khi phi np li, tnh in nng tng ng d tr trong acquy nu coi ncung cp dng in khng i 0,5A:

A. 30h; 324kJ B. 15h; 162kJ C. 60h; 648kJ D. 22h; 489kJCu hi 2: Mch in gm in tr R = 2 mc thnh mch in kn vi ngun = 3V, r = 1 thcng sut tiu th mch ngoi R l:

A. 2W B. 3W C. 18W D. 4,5WCu hi 3: Mt ngun c = 3V, r = 1 ni vi in tr ngoi R = 1 thnh mch in kn. Cng

sut ca ngun in l:A. 2,25W B. 3W C. 3,5W D. 4,5WCu hi 4: Mt mch in kn gm ngun in sut in ng = 6V, in tr trong r = 1 nivi mch ngoi l bin tr R, iu chnh R cng sut tiu th trn R t gi tr cc i. Cngsut l:

A. 36W B. 9W C. 18W D. 24WCu hi 5: Mt mch in kn gm ngun in sut in ng = 3V, in tr trong r = 1 nivi mch ngoi l bin tr R, iu chnh R cng sut tiu th trn R t gi tr cc i. Khi Rc gi tr l:

A. 1 B. 2 C. 3 D. 4Cu hi 6: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Xc nh R bit R > 2, cng sut mch ngoi l 16W:

A. 3 B. 4 C. 5 D. 6 Cu hi7: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Tnh cng dng in v hiu sut ngun in, bit R > 2, cng sut mchngoi l 16W:

A. I = 1A. H = 54% B. I = 1,2A, H = 76,6%C. I = 2A. H = 66,6% D. I = 2,5A. H = 56,6%

Cu hi 8: Hai in tr mc song song vo ngun in nu R1< R2 v R12 l in tr tng ngca h mc song song th:A. R12 nh hn c R1v R2.Cng sut tiu th trn R2 nh hn trn R1.

B.R12 nh hn c R1v R2.Cng sut tiu th trn R2 ln hn trn R1.

C. R12 ln hn c R1 v R2. D. R12 bng trung bnh nhn ca R1 v R2Cu hi 9: Ba in tr bng nhau R1 = R2 = R3 mc nh hnh v. Cngsut tiu th:

A. ln nht R1 B. nh nht R1C. bng nhau R1 v h ni tip R23 D. bng nhau R1, R2 ,

R3Cu hi 10: Hai bng n c hiu in th nh mc ln lt l U1 = 110V, U2 = 220V. Chng ccng sut nh mc bng nhau, t s in tr ca chng bng:

A. B. C. D.

U

R2 R3

R1


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Cu hi 11: bng n 120V 60W sng bnh thng mng inc hiu in th 220V ngi ta mc ni tip n vi in tr ph R. R cgi tr:

A. 120 B. 180 C. 200 D. 240Cu hi 12: Ba in tr bng nhau R1 = R2 = R3 ni vo ngun nh hnhv. Cng sut tiu th :

A. ln nht R1 B. nhnht R1

C. bng nhau R1 v b hai in tr mc song song D. bngnhau R1, R2 v R3

Cu hi 13: Khi hai in tr ging nhau mc song song v mc vo ngun in th cng sut tiuth l 40W. Nu hai in tr ny mc ni tip vo ngun th cng sut tiu th l:

A. 10W B. 80W C. 20W D. 160WCu hi 14: Mc hai in tr R1 = 10 , R2 = 20 vo ngun c hiu in th U khng i. Sosnh cng sut tiu th trn cc in tr ny khi chng mc ni tip v mc song song thy:

A. ni tip P1/P2 = 0,5; song song P1/P2 = 2 B. ni tip P1/P2 = 1,5; song song P1/P2 =0,75C. ni tip P1/P2 = 2; song song P1/P2 = 0,5 D. ni tip P1/P2 = 1; song song P1/P2 = 2

Cu hi 15: Mt bp in gm hai dy in tr R1

v R2. Nu ch dng R

1th thi gian un si

nc l 10 pht, nu ch dng R2 th thi gian un si nc l 20 pht. Hi khi dng R1 ni tip R2th thi gian un si nc l bao nhiu:

A. 15 pht B. 20 pht C. 30 pht D. 10phtCu hi 16: Mt bp in gm hai dy in tr R1 v R2. Nu ch dng R1 th thi gian un sinc l 15 pht, nu ch dng R2 th thi gian un si nc l 30 pht. Hi khi dng R1 song songR2 th thi gian un si nc l bao nhiu:

A. 15 pht B. 22,5 pht C. 30 pht D. 10phtCu hi 17: Mt bn l dng in 220V. C th thay i gi tr in tr ca cun dy trong bn lnh th no dng in 110V m cng sut khng thay i:

A. tng gp i B. tng 4 ln C. gim 2 ln D. gim4 lnCu hi 18: Hai bng n c cng sut nh mc l P1 = 25W, P2= 100W u lm vic bnhthng hiu in th 110V. So snh cng dng in qua mi bng v in tr ca chng:

A. I1.>I2; R1 > R2 B. I1.>I2; R1 < R2 C. I1. R2Cu hi 19: Hai bng n c cng sut nh mc l P1 = 25W, P2= 100W u lm vic bnhthng hiu in th 110V. Khi mc ni tip hai n ny vo hiu in th 220V th:

A. n 1 sng yu, n 2 qu sng d chy B. n 2 sng yu, n 1qu sngd chyC. c hai n sng yu D. c hai n sng bnh thng

Cu hi 20: Hai in tr ging nhau mc ni tip vo ngun in hiu in th U th tng cngsut tiu th ca chng l 20W. Nu chng mc song song vo ngun ny th tng cng sut tiu

th ca chng l:A. 5W B. 40W C. 10W D. 80WCu hi 21: Khi mt ti R ni vo ngun sut in ng v in tr trong r, thy cng sut mchngoi cc i th:

A. = IR B. r =R C. PR= I D. I = /rCu hi 22: Mt ngun in c sut in ng = 12V in tr trong r = 2 ni vi in tr R tothnh mch kn. Xc nh R cng sut ta nhit trn R cc i, tnh cng sut cc i :

A. R= 1, P = 16W B. R = 2, P = 18WC. R = 3, P = 17,3W D. R = 4, P = 21W

U

R2

R3R1


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P N

I . kin thc:nh lut m i vi on mch ch cha R:

RU

=I

Trng hp ngoi in tr, trong mch cn c cc dng c o(Vn k v Ampe k )th cn c vo d kin cho trong bit c phi l dng c o l tng (ngha l Vnk c Rv = , Ampe k c RA = 0) hay khng.

- cng thc R ni tip, R // CH :

* ni tt l:... Trong trng hp khng bit r chiu dng in trong mch in th ta t chn mt chiu

dng in v theo dng in ny m phn bit ngun in no l my pht(dng in i ra t ccdng v i vo cc m), u l my thu (dng in i vo cc dng v i ra t cc m).Nu ta tm c I > 0: chiu dng in ta chn chnh l chiu thc ca dng in trong

mch.Nu ta tm c I < 0: chiu dng in thc trong mch ngc vi chiu ta chn ban

u.

I=R

U

II. Bi tp t lun:1. Cho mch in nh hnh v, Rb l mt bin tr. Hiu in th U giahai u mch in c gi tr khng i. Bit Ampe k c in tr

khngng k, vn k c in tr rt ln. iu chnh bin tr sao cho:

- Khi ampe k ch 0,4 A th vn k ch 24 V.- Khi ampe k ch 0,1 A th vn k ch 36 V.

Tnh hiu in th U v in tr R ? s: 40 , 40 V.

2. Cho mch in nh hnh v:R1 = 3 , R2 = 9 , R3 = 6 .in tr trong ca ampe k khng ng k. UAB = 18 V.

a. Cho R4 = 7,2 th ampe k ch gi tr bao nhiu?

b. iu chnh R4 ampe k ch s 0. Tnh gi tr ca R4 ?

Cu 1 2 3 4 5 6 7 8 9 10p n A A D B A B C A A C

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

Cu 21 22p n B B

13 Ch 3: NH LUT M I VI ON MCH (ch cha R hoc chaR v n un


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s: 0,67 A, 18 .

3. Cho mch in nh hnh v:R1 = 3 , R2 = 9 , R3 = 6 .in tr trong ca ampe k khng ng k. UAB = 18 V.

a. Cho R4 = 7,2 th ampe k ch gi tr bao nhiu?b. iu chnh R4 ampe k ch s 0. Tnh gi tr ca R4 ?

s: 2 A, 180 .

4. Cho mch in nh hnh v, bit UAB = 48 VR1= 2 , R2 = 8 , R3 = 6 , R4 = 16 .

a. Tnh hiu in th gia hai im M v N ?b. Mun o UMN phi mc cc dng ca vnk vo

imno? s: 4V,

im N.5. Xc nh cng dng in qua ampe k theo mch nh hnhv.

Bit RA 0; R1 = R3 = 30 ; R2 = 5 ; R4 = 15 v U = 90 V. s: 5 A.

III. Bi tp trc nghim:

Cu hi 1: Biu thc lin h gia hiu in th, cng dng in v in tr ca hai vt dnmc ni tip v mc song song c dng l:

A. Ni tip ; song song B. Ni tip ; song

song

C. Ni tip ; song song D. Ni tip ; song song

Cu hi 2: Cc dng c in trong nh thng c mc ni tip hay song song, v sao?A. mc song song v nu 1 vt b hng, vt khc vn hot ng bnh thng v hiu in thnh mc cc vt bng hiu in th ca ngunB. mc ni tip v nu 1 vt b hng, cc vt khc vn hot ng bnh thng v cng nh mc ca cc vt lun bng nhauC. mc song song v cng dng in qua cc vt lun bng nhau v hiu in th nhmc ca cc vt bng hiu in th ca ngunD. mc ni tip nhau v hiu in th nh mc ca cc vt bng hiu in th ca ngun, vcng nh mc qua cc vt lun bng nhau

Cu hi 3: Mt bng n in tr 87 mc vi mt ampe k c in tr 1. Hiu in th giahai u on mch l 220V. Tm hiu in th gia hai u bng n:A. 220V B. 110V C. 217,5V D. 188V

Cu hi 4: Gia hai u mng in c mc song song 3 dy dn in tr ln lt l R1 = 4, R2 =5, R3 = 20. Tm hiu in th hai u on mch nu cng dng in trong mch chnh l2,2A:

A. 8,8V B. 11V C. 63,8V D.4,4VCu hi 5: Gia hai u mng in c mc song song 3 dy dn in tr ln lt l R1 = 4, R2 =5, R3 = 20. Tm cng dng in qua R1 nu cng dng in trong mch chnh l 5A:

A. 1,5A B. 2,5A C. 2A D. 0,5A

Cu hi 6: Mt hiu in th nh nhau mc vo hai loi mch: Mch 1 gm hai in tr ging


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nhau u bng R mc ni tip th dng in chy trong mch chnh l I1, mch 2 gm hai intr ging nhau cng u bng R mc song song th dng in chy trong mch chnh l I2. Miquan h gia I1 v I2 l:

A. I1 = I2 B. I2 = 2I1 C. I2 = 4I1 D. I2 = 16I1Cu hi 7: Cho mch in nh hnh v, quan h gia I v I1l:A. I = I1/3 B. I = 1,5I1 C. I = 2I1D. I = 3I1Cu hi 8: Cho mch in nh hnh v. Nu R1 gim xung

th:A. gim th trn R2 gim B. dng in quaR1 l hng sC. dng in qua R1 tng D. cng sut tiuth trn R2 gimCu hi 9: Cho mch in nh hnh v, R = 6, UAB =30V. Cng dng in trong mch chnh v qua nhnh2R ln lt l:A. 2A, 1A B. 3A, 2A C. 2A; 0,67AD. 3A; 1A

Cu hi 10: Cho mch in nh hnh v, R1 = 1, R2 = 2,R3 = 3, R4 = 4,I1 = 2A, tnh UABA. UAB = 10V B. UAB = 11,5V C.UAB = 12VD. UAB = 15,6V

Cu hi 11: Cho mch in nh hnh v, UAB = 30V, cc intr ging nhau u bng 6.Cng dng in trong mchchnh v cng qua R6 ln lt l:

A. 10A; 0,5A B. 1,5A; 0,2A C. 15A; 1A

D. 12A; 0,6A

Cu hi 12:cho mch in nh hnh v. R1 = 10; R2 = R3 =6; R4 = R5 = R6 = 2. Tnh RAB?

A. 10 B. 6 C. 12D. 14

Cu hi 13: bi nh cu 12. Bit cng dng in qua R4 l 2A. Tnh UAB:A. 36V B. 72V C. 90V D. 18V

Cu hi 14: Cho mch in mc nh hnh v. Nu mc vo AB hiuin th UAB = 100V th UCD = 60V, I2 = 1A. Nu mc vo CD: UCD =120V th UAB = 90V. Tnh R1, R2, R3:A. R1 = 120; R2 = 60; R3 = 40 B. R1 = 120; R2 = 40; R3 =60 C. R1 = 90; R2 = 40; R3 = 60D. R1 = 180; R2 = 60; R3 = 90

Cu hi 15: Cho mch in nh hnh v. Nu mc vo AB:UAB =120V th UCD = 30V v I3 = 2A. Nu mc vo CD: UCD = 120V thUAB = 20V. Tnh R1, R2, R3:

A. R1 = 12; R2 = 40; R3 = 20 B. R1 = 6; R2 =

84U

I I1

R2R1U

I I1

C D

A+ _B

R RR

R

C D

A+ _B

R3 R4R2

R1

+A R4

_B R6

R2 R3 R5

R1

R1 R3

A

B D

CR2

R1 R2

A

B D

CR2

R3


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30; R3 = 15C.R1 = 9; R2 = 40; R3 = 30 D. R1 = 18; R2 =

10; R3 = 15

Cu hi 16: Cho mch in nh hnh v. UAB = 20V, R1 = 2, R2 =1, R3 = 6, R4 = 4,K m; tnh cng dng in qua cc intr:

A. I1 = 1,5A; I2 = 3A B. I1 = 2,5A; I2 = 4AC.I1 = 3A; I2 = 5A D.I1 = 3,5A; I2 = 6A

Cu hi 17: bi ging cu 16. Kha K ng. Tnh cng dng in qua R1 v R2 bit Kkhng in tr :

A. I1 = 1,8A; I2 = 3,61A B. I1 = 1,9A; I2 = 3,82A

C. I1 = 2,16A; I2 = 4,33A D.I1 = 2,35A; I2 = 5,16A

Cu hi 18: Mt bng n ghi 3V 3W khi n sng bnh thng in tr n c gi tr l:

A. 9 B. 3 C. 6 D. 12

Cu hi 19: Mt bng n ghi 6V 6W mc vo hiu in th 6V th cng dng in quabng l:

A. 36A B 6A C. 1A D. 12A

Cu hi 20: bng n 120V 60W sng bnh thng mng in c hiu in th 220Vngi ta phi mc ni tip vi n mt mt in tr R c gi tr l:

A. 410 B 80 C. 200 D. 100

Cu hi 21: Cho mch in nh hnh v. R1 = 3, R2 = 2, R3= 3, UAB = 12V. Tnh Rx cng dng in qua ampe k

bng khng:A. Rx = 4 B.Rx = 5 C. Rx = 6

D. Rx = 7

Cu hi 22: Cho mch in nh hnh v cu hi 21. R1 = 3, R2 = 2, R3 = 3, UAB = 12V.Rx =1. Tnh cng dng in qua ampe k, coi ampe k c in tr khng ng k

A. 0,5A B. 0,75A C. 1A D. 1,25A

Cu hi 23: Cho mch in nh hnh v cu hi 21, thay ampe k bng vn k, R1 = 3, R2 = 2,R3 = 1, UAB = 12V. Tnh Rx vn k ch s khng:

A. 2/3 B. 1 C. 2 D. 3Cu hi 24: Cho mch in nh hnh v cu hi 21, thay ampe k bng vn k, R1 = 3, R2 = 2,R3 = 1, UAB = 12V. Vn k ch 2V, cc dng mc vo im M, coi in tr vn k rt ln. TnhRx:

A. 0,1 B. 0,18 C. 1,4 D. 0,28

Cu hi 25: Cho mch in nh hnh v. R1 = 1, R2 = 3, Rv =, UAB = 12V. Kha K m, vn k ch 2V. Tnh R3?

A. 2 B3 C. 4

R1 R3

R2 R4

A+ -B

K

AR1 R3

R2 Rx

A+ -B

VR1 R3

R2 R4

A+ -B

K


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D. 5

Cu hi 26: Cho mch in nh hnh v cu hi 25. R1 = 1, R2 = 3, Rv = , R3 = 5. Kha Kng, vn k ch s khng. Tnh R4?

A. 11 B13 C. 15 D. 17

Cu hi 27: Cho mch in nh hnh v. R1 = 1, R2 = 3, Rv =, UAB = 12V. Kha K ng, vn k ch 1V. Tnh R4?

A. 9 hoc 33 B.9 hoc 18 C. 18 hoc 33D. 12 hoc 24

Cu hi 28: Mt ampe k c in tr bng 9 ch cho dng in ti a l 0,1A i qua. Mun mcvo mch in c dng in chy trong nhnh chnh l 5A m ampe k hot ng bnh thngkhng b hng th phi mc song song vi n in tr R l:

A. 0,1 B. 0,12 C. 0,16 D. 0,18

Cu hi 29: Mt vn k c in tr 10K c th o c ti a hiu in th 120V. Mun mcvo mch in c hiu in th 240V phi mc ni tip vi n mt in tr R l:

A. 5K B. 10K C. 15 K D. 20K

Cu hi 30: Mt ampe k c in tr bng 2 ch cho dng in ti a l 10mA i qua. Mun mcvo mch in c dng in chy trong nhnh chnh l 50mA m ampe k hot ng bnh thngkhng b hng th phi mc vi n in tr R: A. nh hn 2 song song vi ampe k

B. ln hn 2 song song vi ampe k

C. nh hn 2 ni tip vi ampe k D. ln hn 2 ni tip vi ampe k

Cu hi 31: Cho mch in nh hnh v, vn k in tr rt ln, R1= 3, R2 = 2, R3 = 1, UAB = 12V. Vn k ch 3V, cc dng

mc vo im N. Tnh Rx:A. 0,8 B. 1,18 C. 2 D. 2,28

Cu hi 32: Mt vn k c in tr Rv o c hiu in th ti a l 50mV. Mun mc vo mchc hiu in th 20V m vn k khng b hng ngi ta ni vi vn k in tr R:

A. nh hn Rv rt nhiu, song song vi vn k B. ln hn Rv rt nhiu, song songvi vn k

C. nh hn Rv rt nhiu, ni tip vi vn k D. ln hn Rv rt nhiu, ni tipvi vn k

Cu hi 33: bn in tr ging nhau mc ni tip v ni vo mng in c hiu in thkhng i UAB = 132V:Dng vn k c in tr RV khi ni vo A, Cvn k ch 44V. Hi khi vn k ni vo A, D ns ch bao nhiu:

A. 12V B. 20V C. 24VD. 36VCu hi 34: Cho mch in nh hnh v. UAB = 120V, hai vn kc in tr rt ln, R1 c in tr rt nh so vi R2. S ch ca ccvn k l:

A.U1

= 10V; U2

= 110V B. U1

= 60V;

VR1 R3

R2 R4

A+ -B

VR1 R3

R2 Rx

A+ -B

A D C BR R R R+ -

R1 R2

A+ -B

V1 V2


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U2 = 60VC.U1 = 120V; U2 = 0V D.U1 = 0V;

U2 = 120V

Cu hi 35: Mt in k c th o c dng in ti a l 10mA dng lm vn k c th oti a 25V, th ngi ta s dng thm:

A. in tr nh hn 2 mc song song vi in k B. in tr ln hn 2 mc songsong vi in k C. in tr nh hn 2 mc ni tip vi in k D. in tr ln hn 2 mc ni

tip vi in k Cu hi 36: Mt in k c in tr 1, o c dng in ti a 50mA. Phi lm th no sdng in k ny lm ampe k o cng dng in ti a 2,5A:

A. Mc song song vi in k mt in tr 0,2 B. Mc ni tip vi in k mt in tr4C. Mc ni tip vi in k mt in tr 20 D. Mc song song vi in k mtin tr 0,02

Cu hi 37:Mt in k c in tr 2, trn in k c 100 chia, mi chia c gi tr0,05mA. Mun dng in k lm vn k o hiu in th cc i 120V th phi lm th no:

A. Mc song song vi in k in tr 23998 B. Mc ni tip vi in k in tr

23998C. Mc ni tip vi in k in tr 11999 D. Mc song song vi in k intr 11999

Cu hi 38: Mt in k c in tr 24,5 o c dng in ti a l 0,01A v c 50 chia.Mun chuyn in k thnh ampe k m mi chia ng vi 0,1A th phi mc song song vi ink mt in tr:

A. 0,1 B. 0,3 C. 0,5 D. 0,7

Cu hi 39:Mt vn k c in tr 12K o c hiu in th ln nht 110V. Nu mc vn kvi in tr 24K th vn k o c hiu in th ln nht l bao nhiu:

A. 165V B. 220V C. 330V D. 440V

Cu hi 40: Mt ampe k c in tr 0,49 o c dng in ln nht l 5A. Ngi ta mc thmin tr 0,245 song song vi ampe k trn tr thnh h thng c th o c dng in lnnht bng bao nhiu:

A. 10A B. 12,5A C. 15A D. 20A

P NCu 1 2 3 4 5 6 7 8 9 10

p n C C C D B C B A D B

Cu 11 12 13 14 15 16 17 18 19 20p n C C B B B B C B C CCu 21 22 23 24 25 26 27 28 29 30

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

p n C D C D D D B C C B

I. Kin thc:

14 Ch 4: : NH LUT M I VI TON MCH.NH LUT M I VI ON MCH CHA NGUN IN


17/58


18/58

Trong cc trng hp mch c nhiu ngun th cn xc nh xem cc ngun c mc vinhau nh th no: Tnh b, rb thay vo biu thc ca nh lut m ta s tm c I.

rRI

N +=

Bi ton cng c th ra ngc li: Tm in tr hoc tm sut in ng ca ngun. Khi bi ton c th cho cng , hiu in th trn mch hoc cho n sng bnh thng, - Dng ton tnh cng sut cc i m ngun in c th cung cp cho mch ngoi.Ta cn tm biu thc P theo R, kho st biu thc ny ta s tm c R P max v gi tr Pmax.

P = 2

2

2

2

)R(Rr)(

R

rR +=+

XtR

r+R t gi tr cc tiu khi R = r. Khi Pmax =

r.4

2

- Dng ton ghp n ngun ging nhau: Tnh sut in ng, v in tr trong ca b ngun.Kho st cc i, cc tiu: Sut in ng ca b ngun cc i nu cc ngun ni tip nhau, intr trong ca b ngun cc tiu nu cc ngun ghp song song nhau.- Mch cha t in: khng c dng in qua cc nhnh cha t; b qua cc nhnh c t, gii mchin tm cng dng in qua cc nhnh; hiu in th gia hai bn t hoc hai u b t

chnh l hiu in th gia 2 im ca mch in ni vi hai bn t hoc hai u b t.Dng 1: NH LUT M I VI TON MCH.

PP chung: ,rnh lut m i vi ton mch:

rR+=

I

H qu:- Hiu in th mch ngoi (cng l hiu in th gia hai cc dng m ca ngun in):U =

- I.r

- Nu in tr trong r = 0 hay mch h (I = 0) th U = .- Nu in tr mch ngoi R = 0 th I =

r

, lc ny on mch b on mch (Rt nguy

him, v khi I tng ln nhanh t ngt v mang gi tr rt ln.)II.bi tp t lun:1. Tnh hiu in th gia hai cc ca mt ngun c sut in ng l , bit in tr trong v

ngoi l nh nhau ? s:2

2. Nu mc in tr 16 vi mt b pin th cng dng in trong mch bng 1 A. Nu mcin tr 8 vo b pin th cng bng 1,8 A. Tnh sut in ng v in tr trong ca b

pin. s: 18 V, 2 .3. Mt ngun in c sut in ng l 6 V, in tr trong r = 2 , mch ngoi c in tr R.

a. Tnh R cng sut tiu th mch ngoi l 4 W.b. Vi gi tr no ca R cng sut mch ngoi c gi tr cc i? Tnh gi tr ?

s: 4 (1 ); 2 , 4,5 W.4. Mc mt bng n nhvi b pin c sut in ng 4,5 v th vnk cho bit hiu in th giahai u bng n l 4 V v ampe k ch 0,25 A. Tnh in tr trong ca b pin. s: 2 5. Mc mt dy c in tr 2 vi mt pin c sut in ng 1,1 V th c dng in 0,5 A chy quady. Tnh cng dng in nu on mch ? s: 5,5 A.


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6. Dng mt ngun in thp sng ln lt 2 bng n c in tr R1 = 2 v R2 = 8 , khi cng sut tiu th ca hai bng n l nh nhau. Tm in tr trong ca ngun in ? s: 4 .7*. Vn k ch 6 V khi mc vo hai cc ca mt ngun in. Mc thm vo hai cc y mt n Ath vn k ch 3 V. Hy tm s ch ca Vn k khi mc thm n B ging nh n A:

a. Ni tip vi n A.b. Song song vi n A.

8. in tr ca bng n (1) v (2) ln lt l 3 v 12 . Khi ln lt mc tng ci vo ngunin th cng sut tieu th ca chng bng nhau. Tnh:

a. in tr trong ca ngun in.b. Hiu sut ca mi n. s: 6 , 33,3 %, 66,7 %.

9. Cho mch in c s nh hnh v, bit = 12 V, r = 1,1 , R1 = 0,1 . + -a. Mun cho cng sut mch ngi ln nht, R phi c gi tr bng bao , r

nhiu ?a.phi chn R bng bao nhiu cng sut tiu th trn R l ln nht?

tnh cng sut ln nht ? s: 1 ; 2, 4

10. Cho mch in nh hnh trong 1 = 8 V, r1= r2 = 2 . n c ghi 12 V 6 W. 1, r1Xc nh gi tr ca 2 bit rng n sng bnh thng.

s: 2 = 6 V. 2, r2 III. Bi tp trc nghim:Cu hi 1: Cng thc no l nh lut m cho mch in kn gm mt ngun in v mt in trngoi:

A. I = B. UAB = Ir C. UAB = + Ir D. UAB = IAB(R + r)

Cu hi 2: Cho mch in nh hnh v. Biu thc no sau y ng:

A. I1 = B. I3 = 2I2 C. I2R = 2I3R D. I2 = I1 + I3

Cu hi 3: Mt ngun in c in tr trong 0,1 mc thnh mch kn vi in tr 4,8. Khi

hiu in th gia hai cc ngun in l 12V. Tnh sut in ng ca ngun v cng dngin trong mch:

A. 2,49A; 12,2V B. 2,5A; 12,25V C. 2,6A; 12,74V D. 2,9A; 14,2V

Cu hi 4: Cho mch in nh hnh v. S ch ca vn k l:

A. 1V B. 2V C. 3V D. 6V

Cu hi 5: Nu l sut in ng ca ngun in v In l dng ngn mch khi hai cc ngun nivi nhau bng dy dn khng in tr th in tr trong ca ngun c tnh:

A. r = /2In B. r = 2/In C. r = /In D. r = In/

Cu hi 6: Mt ngun in mc vi mt bin tr. Khi in tr ca bin tr l 1,65 th hiu inth hai cc ngun l 3,3V; khi in tr ca bin tr l 3,5 th hiu in th hai cc ngun l3,5V. Tm sut in ng v in tr trong ca ngun:

A. 3,7V; 0,2 B.3,4V; 0,1 C.6,8V;1,95 D. 3,6V; 0,15

Cu hi 7: Cho mch in nh hnh v. Hai pin c sut in ng bng nhau v bng 6V,

r1 = 1, r2 = 2. Tnh cng dng in trong mch v hiu in th gia hai im A v B:

A. 1A; 3V B. 2A; 4V C. 3A; 1V D. 4A; 2V

2RR

I1 I3I2

= 6V

100

100

A

, r1

, r2 B

A

, r1

, r2 B


20/58



A. 0,5A; 1V B. 1A; 1V C. 0A; 2V D. 1A; 2V

Cu hi 9: Cho mch in nh hnh v. Hai pin c sut in ng 1 = 6V, 2 = 3V,


A. 1A; 5V B. 0,8A; 4V C. 0,6A; 3V D. 1A; 2V

Cu hi 10: Tm sut in ng v in tr trong ca b ngun gm 6 cquy mc nh hnh v.

Bit mi cquy c = 2V; r = 1:

A. 12V; 3 B. 6V; 3 C. 12V; 1,5 D. 6V; 1,5

Cu hi 11: Cho mch in nh hnh v. Mi pin c = 1,5V; r = 1.

in tr mch ngoi R = 3,5. Tm cng dng in mch ngoi:

A. 0,88A B. 0,9A C. 1A D. 1,2A

Cu hi 12: Cho mch in nh hnh v. Hai pin c sut in ng 1 = 12V, 2 = 6V,r1 = 3, r2 = 5. Tnh cng dng in trong mch v hiu in th gia hai im A v B:

A. 1A; 5V B. 2A; 8V C. 3A; 9V D. 0,75A; 9,75V


Cng dng in mch ngoi l 0,5A. in tr R l:

A. 20 B. 8 C. 10 D. 12

Cu hi 14: Cho mch in nh hnh v. Bit = 6V, r = 0,5, R1 = R2 = 2,

R3 = R5 = 4, R4 = 6. in tr ca ampe k v dy ni khng ng k.Tm s ch ca ampe k:

A. 0,25A B. 0,5A C. 0,75A D. 1A

Cu hi 15: Cho mch in nh hnh v. Khi dng in qua in tr R5 bng khng th:

A. R1/ R2 = R3/ R4 B. R4/ R3 = R1/ R2

C. R1R4 = R3R2 D. C A v C u ng

Cu hi 16: Cho mch in nh hnh v cu hi 14. Bit = 6V, r = 0,5, R1 = R2 = 2; R3 = R5= 4, R4 = 6. in tr ampe k khng ng k. Cng dng in trong mch chnh l:

A. 0,5A B. 1A C. 1,5A D. 2ACu hi 17: Cho mch in nh hnh v cu hi 14. Bit = 6V, r = 0,5, R1 = R2 = 2,R3 = R5 =4, R4 = 6. in tr ampe k khng ng k. Hiu in th gia hai cc ca ngun in l:

A. 1,5V B. 2,5V C. 4,5V D. 5,5V

Cu hi 18: Cho mch in nh hnh v. Bit = 6,6V; r = 0,12, 1: 6V 3W;

2: 2,5V 1,25W. iu chnh R1 v R2 sao cho 2 n sng bnh thng. Tnh gi tr ca R2:

A. 5 B. 6 C. 7 D. 8

A

1 , r1

2 , r2 B

A B

A

1 , r1

2 , r2 B

RA B

R

C

D

A

A B

R2 R3

R4 R5

C

DAB

R1 R2

R3 R4R5

, r

A BR2

1

2R1 C


21/58

Cu hi 19: Cho mch in nh hnh v cu hi 18. Bit = 6,6V; r = 0,12, 1: 6V 3W; 2:2,5V 1,25W. iu chnh R1 v R2 sao cho 2 n sng bnh thng. Tnh gi tr ca R1:

A. 0,24 B. 0,36 C. 0,48 D. 0,56

Cu hi 20: Mc vn k V1 c in tr R1 vo hai cc ngun in (e,r) th vn k ch 8V. Mcthm vn k V2 c in tr R2 ni tip vi V1 vo hai cc ngun th V1 ch 6V v V2 ch 3V. Tnhsut in ng ca ngun:

A. 10V B. 11V

Cu hi 21: Trong mt mch in kn nu mch ngoi thun in tr RN th hiu sut ca ngunin c in tr r c tnh bi biu thc:

A. H = B. H = C.H = D. H =

Cu hi 22: Cho mch in nh hnh v, b qua cc in tr dy ni v ampe k, = 3V,

r = 1, ampe k ch 0,5A. Gi tr ca in tr R l:

A. 1 B. 2 C. 5 D. 3

Cu hi 23: Cc pin ging nhau c sut in ng 0, in tr trong r0 mc hn hp i xng gmn dy, mi dy c m ngun mc ni tip. B ngun ny mc vi in tr ngoi R th cng

dng in qua in tr R l:A. I = B. I = C. I = D. I =

Cu hi 24: C n ngun ging nhau cng sut in ng e, in tr trong r mc ni tip vi nhauri mc thnh mch kn vi R. Cng dng in qua R l:

A. I = B. I = C. I = D. I =

Cu hi 25: C n ngun ging nhau cng sut in ng e, in tr trong r mc song song vinhau ri mc thnh mch kn vi R. Cng dng in qua R l:

A. I = B. I = C. I = D. I =Cu hi 26: Cho mch in nh hnh v. B qua in tr ca dy ni v ampe k,

bit 1 = 3V, r1 = 1, 2 = 6V, r2 = 1, R = 2,5. Ampe k ch:

A. 2A B. 0,666A C. 2,57A D. 4,5A

Cu hi 27: Cho mch in nh hnh v. B qua in tr ca dy ni v ampe k,

= 30V, r = 3, R1 = 12, R2 = 36, R3 = 18. Xc nh s ch ampe k:

A. 0,741A B. 0,654A C. 0,5A D. 1A

Cu hi 28: Cho mch in nh hnh v. B qua in tr ca dy ni v ampe k, = 30V, r = 3, R1 = 12, R2 = 36, R3 = 18. Xc nh s ch ampe k:

A. 0,75A B. 0,65A C. 0,5A D. 1A

Cu hi 29: Khi mt ti R ni vo ngun c sut in ng , in tr trong r m cng sut mchngoi cc i th:

A. IR = B. r = R C. PR= .I D. I = /r

Cu hi 30: Cho mch in nh hnh v. R1 = R2 = RV = 50, = 3V, r = 0.

B qua in tr dy ni, s ch vn k l:

AR

r

1, r1A

R

2, r2

A

NM

R1 R2 R3

, r

NMR1 R2 R3

A

, r

VR1

R2


22/58

A. 0,5V B. 1V C. 1,5V D. 2V

P NCu 1 2 3 4 5 6 7 8 9 10

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

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

p n C C C C D A A A B B

I. Kin thc:1. nh lut m i vi ton mch: Cng dng in chy trong mch in kn t l

thun vi sut in ng ca ngun in v t l nghch vi in tr ton phn ca mch .

rRI

N += + - (, r)

= I.RN +I.r IVi I.RN = UN : gim th mch ngoi.

I.r: gim th mch trong. UN = - r.I + Nu in tr trong r = 0, hay mch h (I = 0) th UN = .

+ Nu R = 0 thr

I

= , lc ny ngun gi l b on mch.

nh lut m i vi ton mch hon ton ph hp vi nh lut bo ton v chuyn hanng lng.

Theo nh lut bo ton v chuyn ha nng lng ta c: Cng ca ngun in sinh ra trongmch kn bng tng cng ca dng in sn ra mch ngoi v mch trong.A = I.t = (RN + r).I

2.tHin tng on mch xy ra khi ni 2 cc ca mt ngun in ch bng dy dn c in tr

rt nh. Khi on mch, dng in chy qua mch c cng ln v c th gy ra nhiu tc hi.2. nh lut m i vi cc loi on mch: on mch cha my thu: , rTh UAB = + I(R+ r)

Hay UBA = - - I (R +r). on mch cha nhiu ngun in, nhiu in tr: 1, r1 2,

r2Th UAB = 1 - 2 + I (R1+ R2+ r1 +r2).Hay: UBA = 2 - 1 I (R1+ R2+ r1 +r2).

3. Hiu sut ca ngun in:

NNco U

tI

tIUAH ===

..

..

A nguon

ich (%)

4. Mc ngun in:Mc n ngun in ni tip nhau.

b = 1 + 2 + .. + nrb = r1 + r2 + .. + rn

Mc m ngun in ging nhau (0 , r0) song song nhau.

14

Ch 4: : NH LUT M I VI TON MCH.NH LUT M I VI ON MCH CHA NGUN IN


23/58

b = 0 , rb =m

r0

Mc N ngun in ging nhau (0 , r0) thnh m dy, mi dy c n ngun in.

b = n.0 , rb =m

rn 0. .

Mc xung i. Gi s cho 1 > 2. 1, r1 2, r2 b = 1 -2 , rb = r1 + r2 .

*. Hng dn gii bi tp: ch ny c th c cc dng bi tp sau y:

- Tnh cng dng in qua mt mch kn.+ Tnh in tr mch ngoi.+ Tnh in tr ton mch: Rtm = RN + r.

+ p dng nh lut m:rR

IN +

= .

Trong cc trng hp mch c nhiu ngun th cn xc nh xem cc ngun c mc vinhau nh th no: Tnh b, rb thay vo biu thc ca nh lut m ta s tm c I.

rRI

N +=

Bi ton cng c th ra ngc li: Tm in tr hoc tm sut in ng ca ngun. Khi bi ton c th cho cng , hiu in th trn mch hoc cho n sng bnh thng, - Dng ton tnh cng sut cc i m ngun in c th cung cp cho mch ngoi.Ta cn tm biu thc P theo R, kho st biu thc ny ta s tm c R P max v gi tr Pmax.

P = 2

2

2

2

)R(R

r)(

R

rR +=

+

XtR

r+R t gi tr cc tiu khi R = r. Khi Pmax =

r.4

2

- Dng ton ghp n ngun ging nhau: Tnh sut in ng, v in tr trong ca b ngun.

Kho st cc i, cc tiu: Sut in ng ca b ngun cc i nu cc ngun ni tip nhau, intr trong ca b ngun cc tiu nu cc ngun ghp song song nhau.- Mch cha t in: khng c dng in qua cc nhnh cha t; b qua cc nhnh c t, gii mchin tm cng dng in qua cc nhnh; hiu in th gia hai bn t hoc hai u b tchnh l hiu in th gia 2 im ca mch in ni vi hai bn t hoc hai u b t.II.bi tp t lun:1. Tnh hiu in th gia hai cc ca mt ngun c sut in ng l , bit in tr trong vngoi l nh nhau ? s:2. Nu mc in tr 16 vi mt b pin th cng dng in trong mch bng 1 A. Nu mcin tr 8 vo b pin th cng bng 1,8 A. Tnh sut in ng v in tr trong ca b

pin. s:3. Mt ngun in c sut in ng l 6 V, in tr trong r = 2 , mch ngoi c in tr R.

a. Tnh R cng sut tiu th mch ngoi l 4 W.b. Vi gi tr no ca R cng sut mch ngoi c gi tr cc i? Tnh gi tr ?

4. Mc mt bng n nhvi b pin c sut in ng 4,5 v th vnk cho bit hiu in th giahai u bng n l 4 V v ampe k ch 0,25 A. Tnh in tr trong ca b pin. s5. Mc mt dy c in tr 2 vi mt pin c sut in ng 1,1 V th c dng in 0,5 A chy quady. Tnh cng dng in nu on mch ? s:.6. Dng mt ngun in thp sng ln lt 2 bng n c in tr R1 = 2 v R2 = 8 , khi

cng sut tiu th ca hai bng n l nh nhau. Tm in tr trong ca ngun in ? s:


24/58

7*. Vn k ch 6 V khi mc vo hai cc ca mt ngun in. Mc thm vo hai cc y mt n Ath vn k ch 3 V. Hy tm s ch ca Vn k khi mc thm n B ging nh n A:

a. Ni tip vi n A.b. Song song vi n A.

8. in tr ca bng n (1) v (2) ln lt l 3 v 12 . Khi ln lt mc tng ci vo ngunin th cng sut tiu th ca chng bng nhau. Tnh:

a. in tr trong ca ngun in.b. Hiu sut ca mi n.

9. Cho mch in c s nh hnh v, bit = 12 V, r = 1,1 , R1 = 0,1 . + -a. Mun cho cng sut mch ngi ln nht, R phi c gi tr bng bao , r

nhiu ?b.phi chn R bng bao nhiu cng sut tiu th trn R l ln nht?

tnh cng sut ln nht ? s10. Cho mch in nh hnh trong 1 = 8 V, r1= r2 = 2 . n c ghi 12 V 6 W. 1, r1Xc nh gi tr ca 2 bit rng n sng bnh thng.

s:III. Bi tp trc nghim:Cu hi 1: Cng thc no l nh lut m cho mch in kn gm mt ngun in v mt in trngoi:

A. I = B. UAB = Ir C. UAB = + Ir D. UAB = IAB(R + r)

Cu hi 2: Cho mch in nh hnh v. Biu thc no sau y ng:

A. I1 = B. I3 = 2I2 C. I2R = 2I3R D. I2 = I1 + I3

Cu hi 3: Mt ngun in c in tr trong 0,1 mc thnh mch kn vi in tr 4,8. Khi hiu in th gia hai cc ngun in l 12V. Tnh sut in ng ca ngun v cng dngin trong mch:

A. 2,49A; 12,2V B. 2,5A; 12,25V C. 2,6A; 12,74V D. 2,9A; 14,2V

Cu hi 4: Cho mch in nh hnh v. S ch ca vn k l:A. 1V B. 2V C. 3V D. 6V

Cu hi 5: Nu l sut in ng ca ngun in v In l dng ngn mch khi hai cc ngun nivi nhau bng dy dn khng in tr th in tr trong ca ngun c tnh:

A. r = /2In B. r = 2/In C. r = /In D. r = In/

Cu hi 6: Mt ngun in mc vi mt bin tr. Khi in tr ca bin tr l 1,65 th hiu inth hai cc ngun l 3,3V; khi in tr ca bin tr l 3,5 th hiu in th hai cc ngun l3,5V. Tm sut in ng v in tr trong ca ngun:

A. 3,7V; 0,2 B.3,4V; 0,1 C.6,8V;1,95 D. 3,6V; 0,15



A. 1A; 3V B. 2A; 4V C. 3A; 1V D. 4A; 2V



2RR

I1 I3I2

= 6V

100

100

A

, r1

, r2 B

A

, r1

, r2 B


25/58

A. 0,5A; 1V B. 1A; 1V C. 0A; 2V D. 1A; 2V



A. 1A; 5V B. 0,8A; 4V C. 0,6A; 3V D. 1A; 2V

Cu hi 10: Tm sut in ng v in tr trong ca b ngun gm 6 cquy mc nh hnh v.

Bit mi cquy c = 2V; r = 1:

A. 12V; 3 B. 6V; 3 C. 12V; 1,5 D. 6V; 1,5


in tr mch ngoi R = 3,5. Tm cng dng in mch ngoi:

A. 0,88A B. 0,9A C. 1A D. 1,2A



A. 1A; 5V B. 2A; 8V C. 3A; 9V D. 0,75A; 9,75VCu hi 13: Cho mch in nh hnh v. Mi pin c = 1,5V; r = 1.

Cng dng in mch ngoi l 0,5A. in tr R l:

A. 20 B. 8 C. 10 D. 12

Cu hi 14: Cho mch in nh hnh v. Bit = 6V, r = 0,5, R1 = R2 = 2,

R3 = R5 = 4, R4 = 6. in tr ca ampe k v dy ni khng ng k.

Tm s ch ca ampe k:

A. 0,25A B. 0,5A C. 0,75A D. 1ACu hi 15: Cho mch in nh hnh v. Khi dng in qua in tr R5 bng khng th:

A. R1/ R2 = R3/ R4 B. R4/ R3 = R1/ R2

C. R1R4 = R3R2 D. C A v C u ng

Cu hi 16: Cho mch in nh hnh v cu hi 14. Bit = 6V, r = 0,5, R1 = R2 = 2; R3 = R5= 4, R4 = 6. in tr ampe k khng ng k. Cng dng in trong mch chnh l:

A. 0,5A B. 1A C. 1,5A D. 2A

Cu hi 17: Cho mch in nh hnh v cu hi 14. Bit = 6V, r = 0,5, R1 = R2 = 2,R3 = R5 =

4, R4 = 6. in tr ampe k khng ng k. Hiu in th gia hai cc ca ngun in l:A. 1,5V B. 2,5V C. 4,5V D. 5,5V

Cu hi 18: Cho mch in nh hnh v. Bit = 6,6V; r = 0,12, 1: 6V 3W;

2: 2,5V 1,25W. iu chnh R1 v R2 sao cho 2 n sng bnh thng. Tnh gi tr ca R2:

A. 5 B. 6 C. 7 D. 8

Cu hi 19: Cho mch in nh hnh v cu hi 18. Bit = 6,6V; r = 0,12, 1: 6V 3W; 2:2,5V 1,25W. iu chnh R1 v R2 sao cho 2 n sng bnh thng. Tnh gi tr ca R1:

A. 0,24 B. 0,36 C. 0,48 D. 0,56

A

1 , r1

2 , r2 B

A B

A

1 , r1

2 , r2 B

RA B

R

C

D

A

A B

R2 R3

R4 R5

C

DAB

R1 R2

R3 R4R5

, r

A BR2

1

2R1 C


26/58


27/58

I kin thc: on mch cha ngun in: , r

Th UAB = + I(R+ r)Hay UBA = - - I (R +r). on mch cha nhiu ngun in, nhiu in tr: 1, r1 2,

r2Th UAB = 1 - 2 + I (R1+ R2+ r1 +r2).Hay: UBA = 2 - 1 I (R1+ R2+ r1 +r2).

3. Hiu sut ca ngun in:

NNco U

tI

tIUAH ===

..

..

A nguon

ich (%)

4. Mc ngun in:Mc n ngun in ni tip nhau.

b = 1 + 2 + .. + n

rb = r1 + r2 + .. + rnMc m ngun in ging nhau (0 , r0) song song nhau.

b = 0 , rb =m

r0

Mc N ngun in ging nhau (0 , r0) thnh m dy, mi dy c n ngun in.

b = n.0 , rb =m

rn 0. .

Mc xung i. Gi s cho 1 > 2. 1, r1 2, r2 b = 1 -2 , rb = r1 + r2 .

II. Bi tp t lun:1. Cho = 12 V, r = 1 , R l bin tr.

a. iu chnh cho R = 9 . Tm cng ca ngun v nhit lng ta ra trn Rtrong 5 pht ?

b. iu chnh R sao cho in nng tiu th ca on mch cha R trong 2 pht , rbng 3240 J, tnh R ?

c. Vi gi tr no ca R th cng sut tiu th trong R t gi tr cc i ?Tnh gi tr cc i ny ? s: 4320 J, 3240 J. 3 v

3

1 . 36 W (R = r)

2. Cho mch in nh hnh v, 1 = 10 V, 2 = 2 V, r1 = r2 = 1 . R l bin tr. 1 , r1

a. iu chnh R = 10 , tm hiu in th gia hai cc ca ngun 2.Tnh nhit lng ta ra trn R trong 5 pht ? 2, r2 R

b. iu chnh R sao cho hiu in th gia hai cc ca ngun 1 bng khng.Tnh R ?

c. Vi gi tr no ca R th cng sut tiu th trn R t gi tr cc i?Tnh gi tr cc i ny?

s: 1 V, 3000 J; 4 ; 2 , 18 W.3. Mch in nh hnh v. 1 = 6 V, 2 = 3 V, r1 = r2 = 1 . 1

a. Tnh cng dng in v hiu in th ca mi cc ca ngun khi k m.b.* Tnh I qua K khi K ng ?

15 nh lut m cho cc loi on mch


28/58

s: 4,5 A, U1 = 1,5 V, U2 = -1,5 V. 9 A. 24. Cho mch in nh hnh v.R2 = R3 = R4 = 30 . R1= 35 , r = 5 .Rv rt ln, V ch 13,5 V.

a. Tnh sut in ng ca ngun?b. i ch ngun v Vn k, tm s ch ca V ?

s: 18 V, 13,5 V.

5. Cho mch in nh hnh trong 2 = 6 V, r1 = 2 .n ghi 12 V- 6 W. Xc nh gi tr ca 1 v r2 bit n sng thng. 1Hiu in th gia hai cc ca ngun 2 l 5 V.

s: 8 V, 2 2

6. Cho mch in nh hnh v. Bit 1 =12 V, r1 = 1 ; 1 r12 r22 =6 V, r2 = 2 ; 3 = 9 V, r3 = 3 ;R1 = 4 , R2 = 2 , R3 = 3 .Tnh hiu in th gia hai im A B ?

s: 13,6 V. 3 r3

17. Cho mch in nh hnh : 1 = 1,9 V; 2 = 1,7 V; 3 = 1,6 V;r1 = 0,3 ; r2 = r3 = 0,1 . Ampe k A ch s 0. 2Tnh in tr R v cng dng in qua cc mch nhnh.

s: R = 0,8 , I = 2 A, I1 = I2 = 1 A. 38.Cho mch in nh hnh: cho bit 1 = 2 ; R1 = 3 , R2 = 6 ; r2 = 0,4 . 1 2Hiu in th gia hai cc ca ngun 1bng khng. Tnh r1 ?

s: 2,4 9. Cho mch in nh hnh v: = 3v, r = 0,5 . R1 = 2 , R2 = 4 , R4 = 8 , R5 = 100 ,

RA = 0 . Ban u k m v ampe k ch I = 1,2 A.a. Tnh UAB v cng dng in qua mi in tr.b. Tm R3, UMN, UMC.c. Tm cng mch chnh v mi nhnh khi K ng ?

s: 4,8 v, I1 = I2 = 0,4 A. I3 = I4 = 0,8 A.R3 = 4 , UMN = 0 V, UMC = 0,8 V. Khng thay i.

1 r110. Cho mch in nh hnh v:1 = 20V, 2 = 32 V, r1 = 1 , r2 = 0,5 , R = 2 2 r2Xc nh chiu v cng dng in qua mi nhnh ?

s: I1 = 4 A, I2 = 16 A, I = 12 A

III. Bi tp tc nghim:

Cu hi 1: Cho mch in nh hnh v. Phng trnh no din t ng mi

quan h gia cc cng dng in:

A. I1 + I6 = I5 B. I1 + I2 = I3 C. I1 + I4 = I5 D. I1 + I2 = I5 +I6I5

I1

I2I4

I6

I3

4

32

56

10V12V


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Cu hi 13: Cho mch in nh hnh v. 1 = 4,5V; r1 = 1, 2 = 1,8V, RAB = 8,RA = 0. Tm gi tr ca in tr on AC ampe k ch s khng:

A. 1,2 B. 2,4 C. 3,6 D. 4,8

Cu hi 14: Cho mch in nh hnh v. 1 = 4,5V; r1 = 1, 2 = 1,8V, RAB = 8,RA = 0, R = 3. Tm gi tr ca in tr on AC ampe k ch s khng:

A. 3 B. 4 C. 6 D. 8

Cu hi 15: Cho mch in nh hnh v. 1 = 6V; r1 = 2, 2 = 4,5V, r2 = 0,5,RA = 0, R = 2. Tm s ch ca ampe k:

A. 0,5A B. 1A C. 1,5A D. 2A

Cu hi 16:Mt b ngun gm hai ngun 1; r1; 2, r2 khc nhau mc song song vi nhau ri mcvi mch ngoi. Hiu in th hai u b hai ngun trn c biu thc:

A. U = 1 + 2 B. 1/U = 1/1 + 1/2 C. U = |1 - 2 | D. U =

Cu hi 17: Mt b ngun gm hai ngun 1; r1; 2, r2 khc nhau mc song song vi nhau ri mcvi mch ngoi. in tr trong ca b ngun c biu thc:

A. rb = r1 + r2 B. rb = C. rb = |r1 - r2 | D. rb =

Cu hi 18: Ba ngun in ging nhau mi ngun c e = 3V, r = 1 mc nh hnh v.Hiu in th UAB bng:

A. 8/3V B.4V C. 0V D. 5/3V


A. 8/3V B. 4/3V C. 0V D. 5/3V


A. 8/3V B.4/3V C. 0V D. 5/3V

P N

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

IV.Bi tp nng cao hay v kh (cc em th sc nh!):

1. Cng dng in khng i chy qua dy tc ca mt bng n l I=0,273A. Tnh in lng

v s e dch qua tit din thng ca dy tc trong thi gian 1 pht. (1,02.1020 e)

Cu 1 2 3 4 5 6 7 8 9 10p n C C D B D D A A C C

R

A

1 , r1

2 , r2

A BC

A

1 , r1

2 , r2

R

A B

A B

A B


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9. Mt m in c 2 dy dn R1 v R2 un nc. Nu dng dy R1 th nc trong m s si trong

thi gian 10 min. Cn nu dng ring dy R2 th thi gian nc s si l 40 min.

Tnh khong thi gian un si m nc trn trong 2 trng hp:

1) R1 song song vi R2 (8 min)

2) R1 ni tip vi R2 (50 min)

Coi in tr ca dy maiso khng ph thuc vo nhit , hiu sut ca m l 100%

HD: Dng cng thc tR

UQ .

2

= vi Q v U khng i trong mi trng hp

10 (in tr ph thuc nhit )

Mt bn l c hiu in th v cng sut nh mc l 220 V-1,1 KW

1) Tnh in tr R0 v cng dng in nh mc I0 ca bn l

2) h bt nhit ca bn l m vn dng mng in c ht l 220 V ngi ta mc ni tip vi

n mt in tr R= 9 m. Khi bn l ch cn tiu th mt cng sut l P= 800 W.

Tnh cng dng in I, hiu in th U v in tr R ca bn l.

HD: 1) I0= P0/U0=5A; R0=U0/I0=44 m

2) '

''

U

PI = (1) M

R

U

R

UI R

'' 220 == (2) T (1) v (2) ta c U=180V (loi U=40 V)

V khi cng sut khng th bng 80 W c; R=40,5 m

11. Cho mch in nh s hnh v: e=12 V; r=0

R1=3 ; R2=4 ; R3=5

1) Tnh cng dng in chy trong mch (1A)

2) Tnh hiu in th gia 2 cc ca ngun v 2 u in tr R2 (U2=4V)

3) Tnh cng ca ngun in sn ra trong 10 min v cng sut to nhit ca R3 (A=7200J)

4) Tnh hiu sut ca ngun v cng do ngun sn ra trong 1h

1 2. Khi mc in tr R1=500 vo 2 cc ca mt pin mt tri th ht mch ngoi l U

1=0,1

V.Thay in tr R1bng R2=1000 th ht ca mch ngoi by gi l U2=0,15 V

1) Tnh sut in ng v in tr trong ca pin ny

2) Din tch ca pin ny l S=5 cm2 v n nhn c nng

lng nh sng vi cng sut l 2 mW/cm2. R2

Tnh hiu sut H ca pin khi chuyn t nng lng

nh sng thnh nhit nng in tr ngoi R2

HD: Ta dng cng thc U=I.R suy ra I sau p dng e=U+I.r cho 2 trng hp R1,R2

e

R1

R3


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Nng lng nh sng trong 1 s l P=10 mW=0,01 W; cng sut to nhit trn R2 l P2 =I22.R2

Vy H= P2/ P S: e=0,3 V; r=1000 ;H=0,225 %

13. C 36 ngun ging nhau mi ngun S e=12 V v TT r=2 ghp thnh b ngun hn hp

i xng gm n dy song song mi dy gm m ngun ni tip. Mch ngoi l 6 bng n ging ht

nhau c mc song2 .Khi ht mch ngoi l U=120 V v csut mch ngoi 360 W.

1) Tnh in tr mi bng n (cc n sng bnh thng)

2) Tnh m,n3) Tnh cng sut v hiu sut ca ca b ngun trong trng hp ny

HD: 1) P1=P/6=60 W; R1=U2 /P1=240

2) Ta c I=6I1=3 A; R=R1/6=40 ; eb=12m; rb= 2m/n vi m.n=36. Dng L mn=3;m=12;

3) Cng sut ca ngun P=eb.I=432 W; H=U/eb= 83,3 %

4. Cho mch in nh hnh v. B ngun c S eb=42,5V; TT rb=1 ;R1=10 ;R2=15 . Bit

in tr ca cc am pe k v dy ni khng ng k

1) Bit b ngun gm cc pin ging nhau mc theo kiu hn hp i xng,mi pin c S e=1,7V

v in tr trong l r=0,2 . Hi b ngun ny mc th no? ( 5 dy song song x 25 ci ni tip)

2) Bit ampek 1 ch 1,5A. Xc nh s ch A2 v tr s ca R

HD: 2) Tnh UMN=I1R1I2=UMN/R2> I=I1+I2

U=eb-I.rb UR=U-UMN R=10

R

5. Cho mch in sau:R1=4 ;R

2=R

3=6 ;U

AB=33V

1) Mc vo C,D mt A c RA=0; lc ny R4=14 . Tnh s

ch ampe k v chiu dng in qua A (0,5 A)

2) Thay A bng vn k c RV rt ln

a) Tm s ch vn k. Cc + vn k mc vo im no? (3,3 V)

b) iu chnh R4 n khi vn k ch s khng. Tm R4 (9 )

3) Nu iu chnh cho R4=6

Tm in tr tng ngca on mch AB

HD: Dng phng php in th nt

A1

A2

e ,r

R1

R2

R2 R4

R1 R3C

B

D

A

16 n tp Chng II. Dng in khng i


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H vtn:.lpTHPT:

Chng II. Dng in khng iI. H THNG KIN THC TRONG CHNG1. Dng in- Dng in l dng dch chuyn c hng ca cc ht ti in, c chiu quy c l chiu chuynng ca cc ht in tch dng. Tc dng c trng ca dng in l tc dng t. Ngoi ra

dng in cn c th c cc tc dng nhit, ho v mt s tc dng khc.- Cng dng in l i lng c trng nh lng cho tc dng ca dng in. i vi

dng in khng i tht

qI =

2. Ngun inNgun in l thit b to ra v duy tr hiu in th nhm duy tr dng in. Sut in ngca ngun in c xc nh bng thng s gia cng ca lc l lm dch chuyn i tchdng q bn trong ngun in v ln ca in tch q .

E =q

A

My thu in chuyn ho mt phn in nng tiu th thnh cc dng nng lng khc c ch,ngoi nhit. Khi ngun in ang np in, n l my thu in vi sut phn in c tr s bngsut in ng ca ngun in.

3. nh lut m- nh lut m vi mt in tr thun:

R

UI AB= hay UAB = VA VB = IR

Tch ir gi l gim in th trn in tr R. c trng vn ampe ca in tr thun c thl on thng qua gc to .- nh lut m cho ton mch

E = I(R + r) hayrR

I+

=E

- nh lut m cho on mch cha ngun in:

UAB = VA VB = E - Ir, hayr

I ABU+

=E

(dng in chy t A n B, qua ngun t cc m sang cc dng)- nh lut m cho on mch cha my thu

UAB = VA VB = Ir + Ep, hay 'rU

IpAB E-

= (dng in chy t A n B, qua my thu t cc dng sang cc m)4. Mc ngun in thnh b- Mc ni tip:

Eb = E1 + E2 + ...+ Enrb = r1 + r2 + ... + rn

Trong trng hp mc xung i: Nu E1 > E2 thEb = E1 - E2

rb = r1 + r2


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D. Sut in ng ca ngun in l i lng c trng cho kh nng sinh cng ca ngunin v c o bng thng s gia cng ca lc l thc hin khi lm dch chuyn mt intch dng q bn trong ngun in t cc dng n cc m v ln ca in tch q .

2.4 in tch ca lectron l - 1,6.10-19 (C), in lng chuyn qua tit din thng ca dy dntrong 30 (s) l 15 (C). S lectron chuyn qua tit din thng ca dy dn trong thi gian mtgiy l

A. 3,125.1018. B. 9,375.1019. C. 7,895.1019. D. 2,632.1018.2.5 th m t nh lut m l:

2.6 Sut in ng ca ngun in c trng choA. kh nng tch in cho hai cc ca n.B. kh nng d tr in tch ca ngun in.C. kh nng thc hin cng ca ngun in.D. kh nng tc dng lc ca ngun in.

2.7 on mch gm in tr R1 = 100 () mc ni tip vi in tr R2 = 300 (), in tr tonmch l:

A. RTM = 200 (). B. RTM = 300 (). C. RTM = 400 (). D. RTM = 500 ().2.8 Cho on mch gm in tr R1 = 100 (), mc ni tip vi in tr R2 = 200 (), hiu inth gia hai u on mch l 12 (V). Hiu in th gia hai u in tr R

1l

A. U1 = 1 (V). B. U1 = 4 (V). C. U1 = 6 (V). D. U1 = 8 (V).2.9 on mch gm in tr R1 = 100 () mc song song vi in tr R2 = 300 (), in trton mch l:

A. RTM = 75 (). B. RTM = 100 (). C. RTM = 150 (). D. RTM = 400 ().2.10 Cho on mch gm in tr R1 = 100 (), mc ni tip vi in tr R2 = 200 (). t vohai u on mch mt hiu in th U khi hiu in th gia hai u in tr R1 l 6 (V).Hiu in th gia hai u on mch l:

A. U = 12 (V). B. U = 6 (V). C. U = 18 (V). D. U = 24 (V).

Pin v cquy2.11 Pht biu no sau y l ng?A. Trong ngun in ho hc (pin, cquy), c s chuyn ho t ni nng thnh in nng.B. Trong ngun in ho hc (pin, cquy), c s chuyn ho t c nng thnh in nng.C. Trong ngun in ho hc (pin, cquy), c s chuyn ho t ho nng thnh in nng.D. Trong ngun in ho hc (pin, cquy), c s chuyn ho t quang nng thnh in nng.

2.12 Pht biu no sau y l ng?A. Ngun in ho hc c cu to gm hai in cc nhng vo dung dch in phn, trong mt in cc l vt dn in, in cc cn li l vt cch in.

I

o U

A

I

o U

B

I

o U

C

I

o U

D


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B. Ngun in ho hc c cu to gm hai in cc nhng vo dung dch in phn, trong hai in cc u l vt cch in.C. Ngun in ho hc c cu to gm hai in cc nhng vo dung dch in phn, trong hai in cc u l hai vt dn in cng cht.D. Ngun in ho hc c cu to gm hai in cc nhng vo dung dch in phn, trong hai in cc u l hai vt dn in khc cht.

2.13 Trong ngun in lc l c tc dngA. lm dch chuyn cc in tch dng t cc dng ca ngun in sang cc m ca ngun

in.B. lm dch chuyn cc in tch dng t cc m ca ngun in sang cc dng ca ngunin.C. lm dch chuyn cc in tch dng theo chiu in trng trong ngun in.D. lm dch chuyn cc in tch m ngc chiu in trng trong ngun in.

2.14 Pht biu no sau y l khng ng?A. Khi pin phng in, trong pin c qu trnh bin i ha nng thnh in nng.B. Khi acquy phng in, trong acquy c s bin i ho nng thnh in nng.C. Khi np in cho acquy, trong acquy ch c s bin i in nng thnh ho nng.

D. Khi np in cho acquy, trong acquy c s bin i in nng thnh ho nng v nhitnng.

in nng v cng sut in. nh lut Jun Lenx2.15 Pht biu no sau y l khng ng?

A. Cng ca dng in chy qua mt on mch l cng ca lc in trng lm di chuyncc in tch t do trong on mch v bng tch ca hiu in th gia hai u on mch vicng dng in v thi gian dng in chy qua on mch .B. Cng sut ca dng in chy qua on mch bng tch ca hiu in th gia hai u onmch v cng dng in chy qua on mch .

C. Nhit lng to ra trn mt vt dn t l thun vi in tr ca vt, vi cng dng inv vi thi gian dng in chy qua vt.D. Cng sut to nhit vt dn khi c dng in chy qua c trng cho tc to nhit cavt dn v c xc nh bng nhit lng to ra vt n trong mt n v thi gian.

2.16 Nhit lng to ra trn vt dn khi c dng in chy quaA. t l thun vi cng dng in chy qua vt dn.B. t l thun vi bnh phng cng dng in chy qua vt dn.C. t l nghch vi cng dng in chy qua vt dn.D. t l nghch vi bnh phng cng dng in chy qua vt dn.

2.17 Pht biu no sau y l khng ng?A. Nhit lng to ra trn vt dn t l thun vi in tr ca vt.B. Nhit lng to ra trn vt dn t l thun vi thi gian dng in chy qua vt.C. Nhit lng to ra trn vt dn t l vi bnh phng cng dng in cy qua vt.D. Nhit lng to ra trn vt dn t l nghch vi hiu in th gia hai u vt dn.

2.18 Sut phn in ca my thu c trng cho sA. chuyn ho in nng thnh nhit nng ca my thu.B. chuyn ho nhit nng thnh in nng ca my thu.

C. chuyn ho c nng thnh in nng ca my thu.


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D. chuyn ho in nng thnh dng nng lng khc, khng phi l nhit ca my thu.2.19 Pht biu no sau y l khng ng?

A. Sut phn in ca my thu in c xc nh bng in nng m dng c chuyn hothnh dng nng lng khc, khng phi l nhit nng, khi c mt n v in tch dngchuyn qua my.B. Sut in ng ca ngun in l i lng c trng cho kh nng sinh cng ca ngunin v c o bng thng s gia cng ca lc l thc hin khi lm dch chuyn mt intch dng q bn trong ngun in t cc m n cc dng v ln ca in tch q .

C. Nhit lng to ra trn mt vt dn t l thun vi in tr ca vt, vi bnh phng cng dng in v vi thi gian dng in chy qua vt.D. Sut phn in ca my thu in c xc nh bng in nng m dng c chuyn hothnh dng nng lng khc, khng phi l c nng, khi c mt n v in tch dngchuyn qua my.

2.20 Dng mt dy dn mc bng n vo mng in. Dy tc bng n nng sng, dy dn hunh khng sng ln v:

A. Cng dng in chy qua dy tc bng n ln hn nhiu cng dng in chyqua dy dn.

B. Cng dng in chy qua dy tc bng n nh hn nhiu cng dng in chyqua dy dn.C. in tr ca dy tc bng n ln hn nhiu so vi in tr ca dy dn.D. in tr ca dy tc bng n nh hn nhiu so vi in tr ca dy dn.

2.21 Cng ca ngun in c xc nh theo cng thc:A. A = EIt. B. A = UIt. C. A = EI. D. A = UI.

2.22 Cng ca dng in c n v l:A. J/s B. kWh C. W D. kVA

2.23 Cng sut ca ngun in c xc nh theo cng thc:

A. P = EIt. B. P = UIt. C. P = EI. D. P = UI.2.24 Hai bng n 1( 220V 25W), 2 (220V 100W) khi sng bnh thng th

A. cng dng in qua bng n 1 ln gp hai ln cng dng in qua bng n2.B. cng dng in qua bng n 2 ln gp bn ln cng dng in qua bng n1.C. cng dng in qua bng n 1 bng cng dng in qua bng n 2.D. in tr ca bng n 2 ln gp bn ln in tr ca bng n 1.

2.25 Hai bng n c cng sut nh mc bng nhau, hiu in th nh mc ca chng ln lt

l U1 = 110 (V) v U2 = 220 (V). T s in tr ca chng l:A.

2

1

R

R

2

1 = B.1

2

R

R

2

1 = C.4

1

R

R

2

1 = D.1

4

R

R

2

1 =

2.26 bng n loi 120V 60W sng bnh thng mng in c hiu in th l 220V,ngi ta phi mc ni tip vi bng n mt in tr c gi tr

A. R = 100 (). B. R = 150 (). C. R = 200 (). D. R = 250 ().

nh lut m cho ton mch2.27 i vi mch in kn gm ngun in vi mch ngoi l in tr th hiu in th mch

ngoi


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2.38 Cho mt mch in kn gm ngun in c sut in ng E = 12 (V), in tr trong r = 2,5(), mch ngoi gm in tr R1 = 0,5 () mc ni tip vi mt in tr R. cng sut tiuth mch ngoi ln nht th in tr R phi c gi tr

A. R = 1 (). B. R = 2 (). C. R = 3 (). D. R = 4 ().2.39* Cho mt mch in kn gm ngun in c sut in ng E = 12 (V), in tr trong r =2,5 (), mch ngoi gm in tr R1 = 0,5 () mc ni tip vi mt in tr R. cng suttiu th trn in tr R t gi tr ln nht th in tr R phi c gi tr

A. R = 1 (). B. R = 2 (). C. R = 3 (). D. R = 4 ().

nh lut m cho cc loi on mch in. Mc ngun thnh b2.40 Mt mch in kn gm hai ngun in E1, r1 v E2, r2 mc ni tip vi nhau, mch ngoich c in tr R. Biu thc cng dng in trong mch l:

A.21

21

rrRI

++

=EE B.

21

21

rrRI

+

=EE C.

21

21

rrRI

++

=EE D.

21

21

rrRI

+++

=E

2.41 Mt mch in kn gm hai ngun in E, r1 v E, r2 mc song song vi nhau, mch ngoich c in tr R. Biu thc cng dng in trong mch l:

A.21 rrR

2I

++

=E B.

21

21

rrr.rR

I

++

=E C.

21

21

rrr.rR

2I

++

=E D.

21

21

r.rrrR

I

++

=E

2.42 Cho on mch nh hnh v (2.42) trong E1 = 9 (V), r1 = 1,2 (); E2 = 3 (V), r2 = 0,4(); in tr R = 28,4 (). Hiu in th gia hai u on mch UAB = 6 (V). Cng dngin trong mch c chiu v ln l:

A. chiu t A sang B, I = 0,4 (A).B. chiu t B sang A, I = 0,4 (A).C. chiu t A sang B, I = 0,6 (A).D. chiu t B sang A, I = 0,6 (A).

2.43 Ngun in vi sut in ng E, in tr trong r, mc vi in tr ngoi R = r, cng dng in trong mch l I. Nu thay ngun in bng 3 ngun in ging ht n mc ni tipth cng dng in trong mch l:

A. I = 3I. B. I = 2I. C. I = 2,5I. D. I = 1,5I.2.44 Ngun in vi sut in ng E, in tr trong r, mc vi in tr ngoi R = r, cng dng in trong mch l I. Nu thay ngung in bng 3 ngun in ging ht n mc songsong th cng dng in trong mch l:

A. I = 3I. B. I = 2I. C. I = 2,5I. D. I = 1,5I.2.45 Cho b ngun gm 6 acquy ging nhau c mc thnh hai dy song song vi nhau, mi

dy gm 3 acquy mc ni tip vi nhau. Mi acquy c sut in ng E = 2 (V) v in tr trongr = 1 (). Sut in ng v in tr trong ca b ngun ln lt l:A. Eb = 12 (V); rb = 6 (). B. Eb = 6 (V); rb = 1,5 ().C. Eb = 6 (V); rb = 3 (). D. Eb = 12 (V); rb = 3 ().

2.46* Cho mch in nh hnh v (2.46). Mi pin c sut in ng E= 1,5 (V), in tr trong r = 1 (). in tr mch ngoi R = 3,5 ().Cng dng in mch ngoi l:

A. I = 0,9 (A) . B. I = 1,0 (A). C. I = 1,2 (A). D. I = 1,4 (A).

Bi tp v nh lut m v cng sut in

E1, r1 E2, r2 RA B

Hnh 2.42

R

Hnh 2.46


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2.47 Cho mt on mch gm hai in tr R1 v R2 mc song song v mc vo mt hiu in thkhng i. Nu gim tr s ca in tr R2 th

A. st th trn R2 gim. B. dng in qua R1 khng thay i.C. dng in qua R1 tng ln. D. cng sut tiu th trn R2 gim.

2.48 Cho mt mch in kn gm ngun in c sut in ng E = 12 (V), in tr trong r = 2(), mch ngoi gm in tr R1 = 6 () mc song song vi mt in tr R. cng sut tiuth mch ngoi ln nht th in tr R phi c gi tr

A. R = 1 (). B. R = 2 (). C. R = 3 (). D. R = 4 ().

2.49 Khi hai in tr ging nhau mc ni tip vo mt hiu in th U khng i th cng suttiu th ca chng l 20 (W). Nu mc chng song song ri mc vo hiu in th ni trn thcng sut tiu th ca chng l:

A. 5 (W). B. 10 (W). C. 40 (W). D. 80 (W).2.50 Khi hai in tr ging nhau mc song vo mt hiu in th U khng i th cng sut tiuth ca chng l 20 (W). Nu mc chng ni tip ri mc vo hiu in th ni trn th cng suttiu th ca chng l:

A. 5 (W). B. 10 (W). C. 40 (W). D. 80 (W).2.51 Mt m in c hai dy dn R1 v R2 un nc. Nu dng dy R1 th nc trong m s

si sau thi gian t1 = 10 (pht). Cn nu dng dy R2 th nc s si sau thi gian t2 = 40 (pht).Nu dng c hai dy mc song song th nc s si sau thi gian l:A. t = 4 (pht). B. t = 8 (pht). C. t = 25 (pht). D. t = 30(pht).

2.52 Mt m in c hai dy dn R1 v R2 un nc. Nu dng dy R1 th nc trong m ssi sau thi gian t1 = 10 (pht). Cn nu dng dy R2 th nc s si sau thi gian t2 = 40 (pht).Nu dng c hai dy mc ni tip th nc s si sau thi gian l:

A. t = 8 (pht). B. t = 25 (pht). C. t = 30 (pht). D. t = 50 (pht).2.53** Cho mt mch in kn gm ngun in c sut in ng E = 12 (V), in tr trong r =3 (), mch ngoi gm in tr R1 = 6 () mc song song vi mt in tr R. cng sut tiuth trn in tr R t gi tr ln nht th in tr R phi c gi tr

A. R = 1 (). B. R = 2 (). C. R = 3 (). D. R = 4 ().

Thc hnh: o sut in ng v in tr trong ca ngun in2.54 i vi mch in kn gm ngun in vi mch ngoi l in tr th hiu in th mchngoi

A. gim khi cng dng in trong mch tng.B.t l thun vi cng dng in chy trong mch.

C. tng khi cng dng in trong mch tng.D. t l nghch vi cng dng in chy trong mch.2.55 Biu thc no sau y l khng ng?

A.rR

I+

=E B.

R

UI = C. E = U Ir D. E = U + Ir

2.56 o sut in ng ca ngun in ngi ta c th dng cch no sau y?A. Mc ngun in vi mt in tr bit tr s v mt ampek to thnh mt mch kn. Davo s ch ca ampe k cho ta bit sut in ng ca ngun in.


42/58


43/58

2.5 Chn: AHng dn: Biu thc nh lut m I = U/R ng c trng V A l mt ng thng iqua gc to .

2.6 Chn: CHng dn:Sut in ng ca ngun in c trng cho kh nng thc hin cng ca ngunin.

2.7 Chn: CHng dn: in tr ca on mch mc ni tip l R = R1 + R2 +.....+ Rn.

2.8 Chn: BHng dn:- in tr ton mch l: R = R1 + R2 = 300 ().- Cng dng in trong mch l: I = U/R = 0,04 (A).- Hiu in th gia hai u in tr R1 l U1 = I.R1 = 4 (V).

2.9 Chn: AHng dn:

in tr on mch mc song song c tnh theo cng thc: R-1 = R1-1 + R2

-1 suy ra R= 75 ().

2.10 Chn: CHng dn:- in tr ton mch l: R = R1 + R2 = 300 ().- Cng dng in trong mch l: I = U1/R1 = 0,06 (A).- Hiu in th gia hai u on mch l U = I.R = 18 (V).

11. Pin v cquy2.11 Chn: C

Hng dn: Trong ngun in ho hc (pin, cquy), c s chuyn ho t ho nng thnh innng.

2.12 Chn: DHng dn: Ngun in ho hc c cu to gm hai in cc nhng vo dung dch in phn,trong hai in cc u l hai vt dn in khc cht.

2.13 Chn: BHng dn: Trong ngun in lc l c tc dng lm dch chuyn cc in tch dng t ccm ca ngun in sang cc dng ca ngun in.

2.14 Chn: C

Hng dn: Khi np in cho acquy, trong acquy c s bin i in nng thnh ho nng vin nng thnh nhit nng.

12. in nng v cng sut in. nh lut Jun Lenx2.15 Chn: C

Hng dn: Nhit lng to ra trn mt vt dn t l thun vi in tr ca vt, vi bnhphng cng dng in v vi thi gian dng in chy qua vt.

2.16 Chn: BHng dn: Nhit lng to ra trn vt dn khi c dng in chy qua t l thun vi bnh

phng cng dng in chy qua vt dn.


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2.17 Chn: DHng dn: Nhit lng to ra trn mt vt dn t l thun vi in tr ca vt, vi bnh

phng cng dng in v vi thi gian dng in chy qua vt.

Biu thc nh lut Jun Lenx c th vit Q = R.I2.t = tRU2 nh vy pht biu Nhit lng

to ra trn vt dn t l nghch vi hiu in th gia hai u vt dn l khng ng.2.18 Chn: D

Hng dn: Sut phn in ca my thu c trng cho s chuyn ho in nng thnh dng

nng lng khc, khng phi l nhit ca my thu.2.19 Chn: D

Hng dn: Sut phn in ca my thu in c xc nh bng in nng m dng cchuyn ho thnh dng nng lng khc, khng phi l nhit nng, khi c mt n v in tchdng chuyn qua my.

2.20 Chn: CHng dn: Dng mt dy dn mc bng n vo mng in. Dy tc bng n nng sng,dy dn hu nh khng sng ln v in tr ca dy tc bng n ln hn nhiu so vi intr ca dy dn.

2.21 Chn: AHng dn: Cng ca ngun in c xc nh theo cng thc A = EIt.

2.22 Chn: BHng dn: 1kWh = 3,6.106 (J)

2.23 Chn: CHng dn: Cng sut ca ngun in c xc nh theo cng thc P = EI.

2.24 Chn: BHng dn: Hai bng n 1( 220V 25W), 2 (220V 100W) khi sng bnh thng thhiu in th t vo hai u bng n l U = 220 (V), cng sut ca mi bng n ln lt l

P1 = 25 (W) v P2 = 100 (W) = 4P1. Cng dng in qua bng n c tnh theo cngthc I = P/U suy ra cng dng in qua bng n 2 ln gp bn ln cng dng inqua bng n 1.

2.25 Chn: C

Hng dn: in tr ca bng n c tnh theo cng thc R =P

U2 . Vi bng n 1 tao c

R1 =P

U21 . Vi bng n 2 tao c R2 =P

U22 . Suy ra4

1

U

U

R

R22

21

2

1 ==

2.26 Chn: C

Hng dn:- Bng n loi 120V 60W sng bnh thng th hiu in th gia hai u bng n l 120(V), cng dng in qua bng n l I = P/U = 0,5 (A).- bng n sng bnh thng mng in c hiu in th l 220V, ngi ta phi mc nitip vi bng n mt in tr sao cho hiu in th gia hai u in tr l U R= 220 120 =100 (V). in tr ca bng n l R = UR/I = 200 ().

13. nh lut m cho ton mch2.27 Chn: C


45/58

Hng dn: Biu thc nh lut m cho ton mch lrR

I+

= hay E = IR + Ir = U + Ir ta suy

ra U = E Ir vi E, r l cc hng s suy ra khi I tng th U gim.2.28 Chn: D

Hng dn: Nhit lng to ra trn mt vt dn t l thun vi in tr ca vt, vi bnhphng cng dng in v vi thi gian dng in chy qua vt.

2.29 Chn: CHng dn: Biu thc nh lut m cho ton mch trong trng hp mch ngoi cha my

thu l 'rrRI P

++=E-E .

2.30 Chn: C

Hng dn: Cng dng in trong mch l I = )A(5,28,4

12

R

U== .

2.31 Chn: BHng dn:

- Cng dng in trong mch l I = )A(5,28,4

12

R

U== .

- Sut in ng ca ngun in l E = IR + Ir = U + Ir = 12 + 2,5.0,1 = 12,25 (V).2.32 Chn: C

Hng dn:- Khi gi tr ca bin tr rt ln th hiu in th gia hai cc ca ngun in l 4,5 (V). Suyra sut in ng ca ngun in l E = 4,5 (V).- p dng cng thc E = U + Ir vi I = 2 (A) v U = 4 (V) ta tnh c in tr trong cangun in l r = 0,25 ().

2.33 Chn: AHng dn: Cng sut tiu th mch ngoi l P = R.I2, cng dng in trong mch l

rRI

+= E suy ra P = R. 2

rR

+E vi E = 6 (V), r = 2 (), P = 4 (W) ta tnh c R = 1 ().

2.34 Chn: C

Hng dn: p dng cng thc P = R.2

rR

+E ( xem cu 2.33), khi R = R1 ta c P1 =

R1.2

1 rR

+E , khi R = R2 ta c P2 = R2.

2

2 rR

+E , theo bi ra P1 = P2 ta tnh c r = 4 ().

2.35 Chn: B


rR

+E ( xem cu 2.33), vi E = 6 (V), r = 2 () v P =

4 (W) ta tnh c R = 4 ().2.36 Chn: B


rR

+E ( xem cu 2.33), ta c P = E2.

2)rR(R+

=

E2. ++ r2

R

rR

12 E

2.r4

1 suy ra Pmax = E2.

r4

1 xy ra khi R = r = 2 ().

2.37 Chn: D


46/58

Hng dn:- Khi R = R1 = 3 () th cng dng in trong mch l I1 v hiu in th gia hai uin tr l U1, khi R = R2 = 10,5 () th cng dng in trong mch l I2 v hiu in thgia hai u in tr l U2. Theo bi ra ta c U2 = 2U1 suy ra I1 = 1,75.I2.- p dng cng thc E = I(R + r), khi R = R1 = 3 () ta c E = I1(R1 + r), khi R = R2 = 10,5() ta c E = I2(R2 + r) suy ra I1(R1 + r) = I2(R2 + r).

- Gii h phng trnh:

+=+

=

r).(10,5Ir)(3I

1,75.II

21

21 ta c r = 7 ().

2.38 Chn: BHng dn:- in tr mch ngoi l RTM = R1 + R- Xem hng dn cu 2.36: Khi cng sut tiu th mch ngoi ln nht th RTM = r = 2,5 ().

2.39 Chn: CHng dn:- on mch gm ngun in c sut in ng E = 12 (V), in tr trong r = 2,5 (), ni tipvi in tr R1 = 0,5 () c th coi tng ng vi mt ngun in c E = 12 (V), in trtrong r = r + R1 = 3 ().

- Xem hng dn cu 2.36.

14. nh lut m cho cc loi on mch in. Mc ngun thnh b2.40 Chn: D

Hng dn: Mt mch in kn gm hai ngun in E1, r1 v E2, r2 mc ni tip vi nhau,mch ngoi ch c in tr R.- Hai ngun in mc ni tip nn sut in ng E = E1 + E2, in tr trong r = r1 + r2.

- Biu thc cng dng in trong mch l21

21

rrRI

+++

=EE

2.41 Chn: BHng dn: Mt mch in kn gm hai ngun in E, r1 v E, r2 mc song song vi nhau,mch ngoi ch c in tr R.- Hai ngun in mc ni tip nn sut in ng E = E1 = E2, in tr trong r = r1.r2/(r1 + r2).

- Biu thc cng dng in trong mch l

21

21

rr

r.rR

I

++

=E

2.42 Chn: A

Hng dn: Gi s dng in i t A sang B nh hnh v 2.42khi E1 l ngun in, E2 l my thu p dng nh lut m

cho on mch cha my thu:21

AB

rrR

UI

+++

= 21E = 0,4 (A) > 0,

chiu dng in i theo chiu gi s (chiu t A sang B).2.43 Chn: D

Hng dn:

- Cng dng in trong mch khi mch ch c mt ngunR2rR

IEE

=+

= (v R =r)

E1, r1 E2, r2 RA B

Hnh 2.42


47/58

- Thay ngun in trn bng 3 ngun in ging nhau mc ni tip th sut in ng l 3.E,

in tr trong 3.r . Biu thc cng dng in trong mch lR4

3

r3R

3'I

EE=

+= nh vy I=

1,5.I.2.44 Chn: D

Hng dn:

- Cng dng in trong mch khi mch ch c mt ngunR2rR

IEE

=+

= (v R =r)

- Thay ngun in trn bng 3 ngun in ging nhau mc song song th sut in ng l E,in tr trong r/3 . Biu thc cng dng in trong mch l

R4

3

3/rR'I

EE=

+= nh vy I=

1,5.I.2.45 Chn: B

Hng dn: Cho b ngun gm 6 acquy ging nhau c mc thnh hai dy song song vinhau, mi dy gm 3 acquy mc ni tip vi nhau. Mi acquy c sut in ng E = 2 (V) vin tr trong r = 1 ().- Mi dy gm 3 acquy mc ni tip vi nhau nn sut in ng v in tr trong ca midy l Ed = 3E = 6 (V) v rd = 3r = 3 ().

- Hai dy ging nhau mc song song vi nhau nn sut in ng v in tr trong ca bngun ln lt l Eb = Ed = 6 (V); rb = rd/2 = 1,5 ().

2.46* Chn: BHng dn:- Ngun in gm 7 pin mc nh hnh 2.46, y l b ngungm 3 pin ghp ni tip ri li ghp ni tip vi mt b khcgm hai dy mc song song, mi dy gm hai pin mc ni tip.p dng cng thc mc ngun thnh b trong trng hp mc

ni tip v mc song song, ta tnh c sut in ng v intr trong ca b ngun l: E = 7,5 (V), r = 4 ().- p dng cng thc nh lut m cho ton mch

)A(1rR

I =+

=E

15. Bi tp v nh lut m v cng sut in2.47 Chn: B

Hng dn: Cho mt on mch gm hai in tr R1 v R2 mc song song v mc vo mt

hiu in th khng i. Nu gim tr s ca in tr R2 th hiu in th gia hai u in trR1 khng i, gi tr ca in ttr R1 khng i nn dng in qua R1 khng thay i.2.48 Chn: C

Hng dn:

- in tr mch ngoi l RTM =RR

R.R 1+

- Xem hng dn cu 2.36: Khi cng sut tiu th mch ngoi ln nht th RTM = r = 2 ().2.49 Chn: D

Hng dn: Cng sut tiu th trn ton mch l P =R

U2 .

R

Hnh 2.46


48/58

- Khi hai in tr ging nhau mc ni tip th cng sut tiu th l P1 =R2

U2 = 20 (W)

- Khi hai in tr ging nhau song song th cng sut tiu th l P2 =

2

RU2 =4

R2

U2 =80(W)

2.50 Chn: AHng dn: Xem hng dn cu 2.49

2.51 Chn: B

Hng dn: Mt m in c hai dy dn R1 v R2 un nc, trong c 3 trng hp nhitlng m nc thu vo u nh nhau.- Khi dng dy R1 th nc trong m s si sau thi gian t1 = 10 (pht). Nhit lng dy R1 to

ra trong thi gian l Q = R1I12t1 = 1

1

2

tR

U

- Khi dng dy R1 th nc trong m s si sau thi gian t2 = 40 (pht). Nhit lng dy R2 to


2

2

tR

U

- Khi dng c hai dy mc song song th s si sau thi gian t. Nhit lng dy to ra trong

thi gian l Q = tRU2 vi

21 R1

R1

R1 += ta suy ra

21 t1

t1

t1 += t = 8 (pht)

2.52 Chn: DHng dn: Mt m in c hai dy dn R1 v R2 un nc, trong c 3 trng hp nhitlng m nc thu vo u nh nhau.- Khi dng dy R1 th nc trong m s si sau thi gian t1 = 10 (pht). Nhit lng dy R1 to


1

2

tR

U

- Khi dng dy R1 th nc trong m s si sau thi gian t2 = 40 (pht). Nhit lng dy R2 to


2

2t

RU

- Khi dng c hai dy mc ni tip th s si sau thi gian t. Nhit lng dy to ra trong thi

gian l Q = tR

U2 vi R = R1 + R2 ta suy ra t = t1 + t2 t = 50 (pht)

2.53 Chn: BHng dn:- on mch gm ngun in c sut in ng E = 12 (V), in tr trong r = 3 (), mchngoi gm in tr R1 = 6 () mc song song vi mt in tr R, khi mch in c th coi

tng ng vi mt ngun in c E = 12 (V), in tr trong r = r // R1 = 2 (), mch ngoigm c R- Xem hng dn cu 2.36. Cng sut tiu th trn R t gi tr max khi R = r = 2 ()

16. Thc hnh: o sut in ng v in tr trong ca ngun in2.54 Chn: A

Hng dn: p dng nh lut m cho ton mch ta c U = E Ir vi E = hng s, khi I tngth U gim.

2.55 Chn: C


49/58

Hng dn:

- Biu thc nh lut m cho ton mch:rR

I+

=E E = U + Ir

- Biu thc nh lut m cho on mch:R

UI =

2.56 Chn: DHng dn:

- Biu thc nh lut m cho ton mch: rRI +=

E

, khi R rt ln th I 0 khi E = U +Ir U- Mc ngun in vi mt vn k c in tr rt ln to thnh mt mch kn. Da vo s chca vn k cho ta bit sut in ng ca ngun in.

2.57 Chn: CHng dn:- Khi gi tr ca bin tr rt ln th hiu in th gia hai cc ca ngun in l 4,5 (V). Suyra sut in ng ca ngun in l E = 4,5 (V).- p dng cng thc E = U + Ir vi I = 2 (A) v U = 4 (V) ta tnh c in tr trong ca

ngun in l r = 0,25 ().2.58 Chn: C

Hng dn: o c hiu in th v cng dng in trong hai trng hp ta c h

phng trnh:

+=

+=

rIU

rIU

22

11

Egii h phng trnh ta c E v r.

H vtn:.lpTHPT:

Chng II. Dng in khng iI. H THNG KIN THC TRONG CHNG1. Dng in- Dng in l dng dch chuyn c hng ca cc ht ti in, c chiu quy c l chiu chuynng ca cc ht in tch dng. Tc dng c trng ca dng in l tc dng t. Ngoi ra

dng in cn c th c cc tc dng nhit, ho v mt s tc dng khc.- Cng dng in l i lng c trng nh lng cho tc dng ca dng in. i vi

dng in khng i tht

qI =

2. Ngun inNgun in l thit b to ra v duy tr hiu in th nhm duy tr dng in. Sut in ngca ngun in c xc nh bng thng s gia cng ca lc l lm dch chuyn i tchdng q bn trong ngun in v ln ca in tch q .

E =q

A

16 n tp Chng II. Dng in khng i


50/58

My thu in chuyn ho mt phn in nng tiu th thnh cc dng nng lng khc c ch,ngoi nhit. Khi ngun in ang np in, n l my thu in vi sut phn in c tr s bngsut in ng ca ngun in.

3. nh lut m- nh lut m vi mt in tr thun:

R

UI AB= hay UAB = VA VB = IR

Tch ir gi l gim in th trn in tr R. c trng vn ampe ca in tr thun c th

l on thng qua gc to .- nh lut m cho ton mch

E = I(R + r) hayrR

I+

=E

- nh lut m cho on mch cha ngun in:

UAB = VA VB = E - Ir, hayr

I ABU+

=E

(dng in chy t A n B, qua ngun t cc m sang cc dng)- nh lut m cho on mch cha my thu

UAB = VA VB = Ir + Ep, hay'r

UIpAB E-=

(dng in chy t A n B, qua my thu t cc dng sang cc m)4. Mc ngun in thnh b- Mc ni tip:

Eb = E1 + E2 + ...+ Enrb = r1 + r2 + ... + rn

Trong trng hp mc xung i: Nu E1 > E2 thEb = E1 - E2

rb = r1 + r2v dng in i ra t cc dng ca E1.- Mc song song: (n ngun ging nhau)

Eb = E v rb =n

r

4. in nng v cng sut in. nh lut Jun Lenx- Cng v cng sut ca dng in on mch (in nng v cng sut in on mch)

A = UIt; P = UI- nh lut Jun Lenx:

Q = RI2t- Cng v cng sut ca ngun in:

A = EIt; P = EI- Cng sut ca dng c tiu th in:

Vi dng c to nhit: P = UI = RI2 =R

U2

Vi my thu in: P = EI + rI2(P /= EI l phn cng sut m my thu in chuyn ho thnh dng nng lng c ch, khng

phi l nhit)


51/58

- n v cng (in nng) v nhit lng l jun (J), n v ca cng sut l ot (W).

II. CU HI V BI TPDng in khng i. Ngun in

2.1 Pht biu no sau y l khng ng?A. Dng in l dng cc in tch dch chuyn c hng.B. Cng dng in l i lng c trng cho tc dng mnh, yu ca dng in v co bng in lng chuyn qua tit din thng ca vt dn trong mt n v thi gian.

C. Chiu ca dng in c quy c l chiu chuyn dch ca cc in tch dng.D. Chiu ca dng in c quy c l chiu chuyn dch ca cc in tch m.

2.2 Pht biu no sau y l khng ng?A. Dng in c tc dng t. V d: nam chm in.B. Dng in c tc dng nhit. V d: bn l in.C. Dng in c tc dng ho hc. V d: acquy nng ln khi np in.D. Dng in c tc dng sinh l. V d: hin tng in git.

2.3 Pht biu no sau y l ng?

A. Ngun in l thit b to ra v duy tr hiu in th nhm duy tr dng in trong mch.Trong ngun in di tc dng ca lc l cc in tch dng dch chuyn t cc dngsang cc m.B. Sut in ng ca ngun in l i lng c trng cho kh nng sinh cng ca ngunin v c o bng thng s gia cng ca lc l thc hin khi lm dch chuyn mt intch dng q bn trong ngun in t cc m n cc dng v ln ca in tch q .C. Sut in ng ca ngun in l i lng c trng cho kh nng sinh cng ca ngunin v c o bng thng s gia cng ca lc l thc hin khi lm dch chuyn mt intch m q bn trong ngun in t cc m n cc dng v ln ca in tch q .D. Sut in ng ca ngun in l i lng c trng cho kh nng sinh cng ca ngunin v c o bng thng s gia cng ca lc l thc hin khi lm dch chuyn mt intch dng q bn trong ngun in t cc dng n cc m v ln ca in tch q .

2.4 in tch ca lectron l - 1,6.10-19 (C), in lng chuyn qua tit din thng ca dy dntrong 30 (s) l 15 (C). S lectron chuyn qua tit din thng ca dy dn trong thi gian mtgiy l

A. 3,125.1018. B. 9,375.1019. C. 7,895.1019. D. 2,632.1018.2.5 th m t nh lut m l:

2.6 Sut in ng ca ngun in c trng choA. kh nng tch in cho hai cc ca n.

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CHUYÊN ĐỀ 2 - DÒNG ĐIỆN KHÔNG ĐỔI