CNG N TP CHNG II: DNG IN KHNG ICH 1: GHP IN TR V NH LUT M CHO ON MCH CHA R *) Mt s bi tp c bn. Bi 1: Cho mch in nh hnh v: R1 R2 R1 = 2, R2 = 4, R3 = 6, UAB = 9V; A B Tnh RAB , IAB, I cc nhnh. S: IAB = 3A. R3 Bi 2: Cho mch in nh hnh v: Bit R1 = 4 , R3 = 5 , R3=20 . R2 a. Tm in tr tng ng RAB ca on mch? A R1 B b. Tm hiu in th UAB v cng dng trong mi nhnh R3 nu cng trong mch chnh l 5A? S: a. 2; b. 10V; 2,5A; 2A; 0,5A Bi 3: Cho mch in nh hnh v: R1 D R2 Bit R1 = 1 , R2=R3 = 2 , R4 = 0,8 , UAB = 6V. a. Tm in tr tng ng ca mch? A R4 B b. Tm cng dng in qua cc in tr v R3 hiu in th gia hai u mi in tr? C c. Tnh hiu in th UAD S: a. 2; b. I1 = I2 =1,2A; I3 = 1,8A. I4 = 3A U1 =1,2V; U2 = 2,4V; U3 = 3,6V; U4 =2,4V; c. UAD = 3,6V. Bi 4: C mch in nh hnh v: R2 R M 3 Cho R1 = 12 , R2=4 , R3 = 6 , UAB = 24 V. Tnh cng dng in qua mi in tr v A R1 B hiu in th UMN, UAN trong hai trng hp: R R4 a. Khi R4 = 6 , R5 = 9 . N 5 b. Khi R4 = 7 , R5 = 8 . S: a. I1= 4/3A; I2= I3= 0,8A ; I4= I5= 8/15UMN = 0 ; UAN = 19,2V. b. I1= 4/3A; I2= I3= 0,8A ; I4= I5= 8/15A, UMN = 8/15V ; UAN = 296/15V = 19,73V. Bi 5: Cho mch in nh hnh : UAB = 20V. Bit in tr ca kha K khng ng k. R1 R4 M R1 = 2 ; R2 = 1 ; R3 = 6 ; R4 = 4 . Tnh cng dng in qua cc in tr trong cc trng hp : B A K a) K m ; R2 R3 b) K ng. S : a) I1 = I 3 = 2,5A ; I2 = I4 = 4A. N b) I1 2,17A ; I2 4,33A ; I3 2,6A ; I4 3,9A.A *) Mt s bi tp nng cao. Bi 6. Cho mch in nh hnh v : UAB = 18V khng i. R1 = R2 = R3 = 6 ; R4 = 2 ; a) Ni M v B bng mt vn k c in tr rt ln. Tm s ch ca vn k. b) Ni M v B bng mt ampe k c in tr rt nh. Tm s ch ca ampe k v chiu dng in qua ampe k. M S : a) 12V ; b) 3,6A, chiu t M n B. Bi 7. Cho mch in nh hnh : UMN = 4V ; R1 = R2 = 2 ; R3 = R4 = R5 = 1 ; RA 0 ; RV = . N a) Tnh RMN. b) Tnh s ch ca ampe k v vn k. R1 R2 MR4 R1 R5 R2 R3

N R3

R4

B

V

A

S : a) RMN = 1 ; b) 2A ; 1V. Bi 8. Cho mch in nh hnh: UAB = 7,2V khng i ; R1 = R2 = R3 = 2 , R4 = 6 . in tr ca ampe k v ca kha K nh khng ng k. Tnh s ch ca ampe k khi: a) K m. b) K ng. S: a) 0,4A ; b) 1,2A.

R3 R2

A

K

U + R4 B

M

A

N R1

Bi 9. Cho mch in nh hnh : UAB = 12V khng i ; R1 = R4 = 2 ; R2 = 6 ; R3 = 1 . R2 R4 a) Tnh RAB v cng dng in qua mi in tr. R1 D A B b*) Mc t in C = 10 F vo mch in theo hai trng hp sau : R3 * Mc vo hai u DB ; * Mc ni tip vi R3. Tnh in tch ca t in trong mi trng hp. 26 54 6 48 S : a) RAB = 2,9 ; I1= I = A 4,15A ; I2 = I4 = A 0,46A ; I3 = A 3,69A. 9 13 13 13 48 R4 b) * q = .10-5C 3,7.10-5C ; * q = 9,6.10-5C. A 13 Bi 10. Cho mch in nh hnh: UAB = 18V khng i ; R1 = R2 = R3 = R4 = 6 ; A B R1 C R2 U . RA 0 ; RV + D R a) Tnh s ch ca vn k, ampe k. 3 b) i ch ampe k v vn k cho nhau. V Tnh s ch ca ampe k v vn k lc ny. S : a) IA = 1,2A ; UV = 7,2V ; b) UV = 0 ; IA = 2A. R1 M R2 Bi 11. Cho mch in nh hnh v : UAB = 24V ; R1 = 2 ; R2 = 10 ; R3 = 6 . A B V a) Vn k ch s khng, tnh R4. b) iu chnh R4 vn k ch 2V. Tm gi tr ca R4 khi . Cc dng R4 R3 N ca vn k ni vi im no ? S : a) R4 = 30 ; b) * UCD = 2V th R4 = 18 ; * UCD = -2V th R4 = 66 . R2 R3 A B D Bi 12. Cho mch in nh hnh: UAB = 90V ; R1 = R3 = 45 ; R2 = 90 . Tm R4, bit khi R4 K m v khi K ng cng dng in qua R4 l nh nhau. R1 S : R4 = 15 .C K

Bi 13. C mt s in tr ging nhau, mi in tr l R0 = 4 . Tm s in tr t nht v cch mc c in tr tng ng R = 6,4 . s: Mch gm 5 in tr R0 Bi 14. Cho mch in c s nh hnh v R1 = 1 , R2 = 0,4 , R3 = 2 , R4 = 6 . R5 = 1 . UAB = 6V. Tnh cng dng in qua mi in tr v in tr tng ng ca mch in s: I1 = 4A, I2 = 5A, I3 = 1,5A, I4 = 0,5A, I5 = 1A RAB = 1,1

R1 A R3

M

R2 R5 B

N

R4

CH 2: IN NNG, CNG SUT IN Bi 1. Cho mch in nh hnh, trong U = 9V, R1 = 1,5 . Bit hiu

in th hai u R2 = 6v. Tnh nhit lng ta ra trn R2 trong 2 pht ? s: 1440 J. Bi 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 l 18 W. Hy xc nh R1 v R2 ? s: R1 = 24 , R2 = 12 , hoc ngc li. Bi 3*. Hai bng n 1 ghi 6v 3 W v 2 ghi 6V - 4,5 W c mc vo mch in nh hnh v. Ngun in c hiu in th U khng thay i. a. Bit ban u bin tr Rb v tr sao cho 2 n sng Rb bnh thng. Tm in tr ca bin tr lc ny ? Trn mch in, u l 1, u l 2 ? b. Gi s t v tr ban u ta di chuyn bin tr con chy sang phi mt cht th sng cc n thay i th no ? R3 s: Rb = 24 Bi 4. Cho mch in nh hnh vi U = 9V, R1 = 1,5 , R2 = 6 . R2 Bit cng dng in qua R3 l 1 A. R1 a. 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. Bi 5. 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). R1 s: 1980000 J. (hay 0,55 kw). 9900 ng. R3 Bi 6: Cho mch in nh hnh v: U = 12 V; R1 = 24 , R3 = 3,8 . R2 Ra = 0,2 . Am pe k ch 1A. Tnh: a. in tr R2. A Ra b. Nhit lng ta ra trn R1 trong thi gian 5 pht. c. Cng sut ta nhit trn R2. S: a. R2 = 12 . b.. Q = 800J c. 16/3W U1 2 Bi 7: C hai bng n: 1(120V- 60W); 2(120V- 45W) R1 c mc vo hiu in th 240 V nh hai hnh v: R2 a. Tnh in tr R1 v R2 hai cch mc. 2 Bit rng cc n sng bnh thng. b. Tnh cng sut tiu th ca mch in trong hai trng hp trn. U U S: a. R1 = 960/7 v R2 = 960; b. P1 = 210W ; P2 = 120W Bi 8*. Mt m in c hai dy dn R1 v R2 un nc. Nu dng dy R1 th nc trong m s si sau khong thi gian 40 pht. Cn nu dng dy R2 th nc s si sau 60 pht. Vy nu dng c hai dy mc song song th m nc s si sau khong thi gian l bao nhiu ? (Coi in tr ca dy thay i khng ng k theo nhit ). Cng cu hi nu cc day mc ni tip? s: 24 pht ; 100 pht. 1

R Bi 9. Ba in tr ging nhau c mc nh hnh, R3 nu cng sut tiu th trn in tr (1) l 3 W th R cng sut ton mch l bao nhiu ? s: 18 W. Bi 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 th cng sut ca in tr (3) l bao nhiu ? s: 54 W. Bi 11. Mt bp in c ni vi hiu in th U = 120V c cng sut P = 600W c dng un si 2 lt nc (c = 4200 J/kg.) t 20 0C n 1000C. Bit hiu sut ca bp l H = 80%. Tm thi gian un nc v in nng tiu th. s: 23,3 pht ; 0,2 kW Bi 12*. Hai n 1 (12V - 7,2W) v 2 (16V - 6,4W) c mc ni tip ri mc vo ngun U = 40V. Hi phi dng ti thiu bao nhiu in tr ph, cch mc v cc gi tr ca cc in tr hai n sng bnh thng. s: R1 nt 1 nt (2 // R2); R1 = 20 , R2 = 80

CH 3: NH LUT M CHO TON MCH Bi 1: Cho mch in Trong ngun in c in tr trong r = 1 . Cc in tr ca mch ngoi R1 = 6 , R2 = 2 , R3 = 3 mc ni tip nhau. Dng in chy trong mch l 1A. a. Tnh sut in ng ca ngun in v hiu sut ca ngun in. b. Tnh cng sut ta nhit ca mch ngoi v hiu in th hai u mi in tr, S: a. = 12V; H = 91,67% ; b. P = 11W; U1 = 6V; U2 = 2V; U3 = 3V Bi 2: Khi mc in tr R1 = 10 vo hai cc ca mt ngun in th dng in chy trong mch l 2A, khi ni mc in tr R2 = 14 vo hai cc ca mt ngun in th dng in chy trong mch l 1,5 A . Tnh sut in ng v in tr trong ca ngun in. S: = 24V; r = 2 Bi 3: Khi mc in tr R1 = 4 vo hai cc ca mt ngun in th dng in chy trong mch l 0,5A, khi ni mc in tr R2 = 10 vo hai cc ca mt ngun in th dng in chy trong mch l 0,25 A . Tnh sut in ng v in tr trong ca ngun in. S: = 3V; r = 2. Bi 4: Khi mc in tr R1 vo hai cc ca mt ngun in c in tr r = 4 th dng in chy trong mch l 1,2A, khi mc thm mt in tr R 2 = 2 ni tip vi R1 vo mch in th dng in chy trong mch l 1 A . Tnh sut in ng ca ngun in v in tr R1. S: = 12V; R1 = 6. Bi 5: Khi mc in tr R1= 10 vo hai cc ca mt ngun in c sut in ng = 6V th cng sut ta nhit trn in tr l P = 2,5W. Tnh hiu in th hai u ngun in v in tr trong ca ngun in. S: U = 5V; r = 2 , r Bi 6: Cho mch in c s nh hnh v. = 4,5V v r = 1 . R1 R1 = 3 , R2 = 6 . a. Tnh cng dng in qua mch chnh v qua in tr? R2 b. Cng sut ca ngun, cng sut tiu th mch ngoi , cng sut hao ph v hiu sut ca ngun? S: a. I = 1,5A; I1=1A; I2 = 0,5A; b. PN = 6,75W; P = 4,5W; PHP = 2,25W; H = 67% Bi 7: Cho mch in c s nh hnh v. = 12V v r = 1 . R1 = 6 , R2 = R3 = 10 . ,r a. Tnh cng dng in chy trong mch v hiu in th hai u mi in tr. b. Tnh in nng tiu th ca mch ngoi trong R1 R3 10 pht v cng sut ta nhit mi in tr. c. Tnh cng ca ngun in sn ra trong 10 pht R2 v hiu sut ca ngun in. S: a. I = 1A; U1 = 6V; U2 = U3 = 5V; b. A = 6600J; P1 = 6W; P2 = P3 = 2,5W; c.AN = 7200J; H = 91,67%, r

Bi 8: C mch in nh hnh v. Ngun in c sut in ng = 12V, c in tr trong r = 1 . n c ghi 6V 3W. Tnh gi tr ca bin tr Rb n sng bnh thng. S: R = 11 Bi 9: C mch in nh hnh v. Ngun in c sut in ng = 24V v c in tr trong r = 1 . Trn cc bng n c ghi: 1( 12V- 6W), 2(12V 12W), in tr R = 3 . a. Cc bng n sng nh th no? Tnh cng dng in qua cc bng n.

Rb

,r

R

1 2

b. Tnh cng sut tiu th ca mch in v hiu sut ca ngun in. S:a. I = 2A; I1 = 1/3A; I2 = 2/3A. b. P = 44W; H = 91,67%. Bi 10: C mch in nh hnh v. Ngun in c sut in ng = 18V v c in tr trong r = 1 . Trn cc bng n c ghi: 1( 12V- 12W), 2(12V -6W), bin tr R c gi tr bin thin t 0 n 100 . a. iu chnh R = 6 . Tnh cng dng in chy qua cc bng n v in tr. So snh sng ca hai bng n. b. iu chnh R bng bao nhiu n 1 sng bnh thng. S: a. IR = 0,808A; I1 = 1,01A; I2 = 0,202A. b. R = 120/19 Bi 11. Cho mch in c s nh hnh v: Trong : E = 1,2 V, r = 0,1 , R1 = R3 = 2 . R2 = R4 = 4 . Tnh I mch chnh, hiu in th gia hai im A, B. s: I = 0,2A ; U = 1,08 V Bi 12: Cho mch in nh hnh v: R1 = R2 = 6 , R3 = 3 , r = 5 , RA = 0. Ampe k A1 ch 0,6A. Tnh sut in ng ca ngun v s ch ca Ampe k A2. S: = 5,2V ; Ampe k A2 ch 0,4A. Bi 13: Cho mch in nh hnh v: = 15V, R = 5 ,1 (6V 9W). a. K m, n 1 sng bnh thng. Tm s ch ca ampe k v in tr trong ca ngun. b. K ng. Ampe k ch 1A v n 2 sng bnh thng. Bit R2 = 5. Hi n 1 sng th no? Tnh cng sut nh mc ca 2. S: a. Ampe k ch 1,5A ; r = 1 b. n 1 sng mnh; P2 = 5W. Bi 14: Cho mch in nh hnh v. Ngun in c sut in ng = 7,8V,v in tr trong r = 0,4 . Cc in tr mch ngoi R1 = R2 = R3 = 3 , R4 = 6 . a. Tnh cng dng in chy qua cc in tr v hiu in th hai u mi in tr. b. Tnh hiu in th gia hai im C v D. c. Tnh hiu in th hai u ngun in v hiu sut ca ngun in. S: a. I1 = I2 = 1.17A ; I3 = I4 = 0,78A U1 = U2 = 3,51V ; U3 = 2,34V ; U4 = 4,68V b. UCD = -1,17V. c. UAB = 7,02V ; H = 90%. Bi 15: Cho mch in nh hnh v. Ngun in c sut in ng = 21V, v in tr trong r = 1 . Cc in tr mch ngoi R1 = 2 , R2 = 4 , R3 = R4 = 6 , R5 = 2 . a. Tnh cng dng in chy qua cc in tr v hiu in th hai u mi in tr . Tnh cng sut tiu th ca mch ngoi. b. Tnh hiu in th gia hai im C v D. c. Tnh hiu sut ca ngun in. S: a. I1 = I2 = 2A ; I3 = I4 = 1A ; I5 = 3A U1 = 4V; U2 = 8V ; U3 = U4 = 6V ; U5 = 6V ; P = 54W. b. UCD = 2V. c. H = 85,7%.

,r

1

2 R

E,r

B R4 N

R1 A R2 MR1

A 1 11 1 1 1

R3R2A 2

R3

,r2 ,r1 A R 2 A K B

R1 A R3

C D

R2 R4 B

,r

R1 A R5 R3

C

R2 B

D R4

,r

,r

D

R4

R1 R3 C

R4 B

Bi 16: Cho mch in nh hnh v. Ngun in c sut in ng = 12V,v in tr trong r = 0,1 . Cc in tr mch ngoi R1 = R2 = 2 ,R3 = 4 , R4 = 4,4 . a. Tnh cng dng in chy qua cc in tr v hiu in th hai u mi in tr. b. Tnh hiu in th UCD, UAB. Tnh cng sut tiu th ca mch ngoi v hiu sut ngun in. S: a. I1 =1,5A; I2 =I3 = 0,5A;I4 = 2A ; U1 =3V U2 = 1V; U3 =2V; U4 = 8,8V. b. UCD = 10,8V; UAB = 3V. c. P = 23,6W; H = 98,3%. Bi 17: Cho mch in nh hnh v. Ngun in c sut in ng = 6V, v in tr trong r = 0,5 . Cc in tr mch ngoi R1 = R2 = 2 , R3 = R5 = 4 , R4 = 6 . in tr ca ampe k khng ng k. a. Tnh cng dng in chy qua cc in tr v hiu in th hai u mi in tr. b. Tm s ch ca ampe k, tnh cng sut ta nhit ca mch ngoi v hiu sut ngun in. S: a.I1=1A; I2 =0,75A; I4 = 0,25A;I3 = I5 = 0,5A ; U1=2V; U2 =U4 = 1,5V ; U3 =U5 = 2V. b. IA = 0,25A; P = 5,5W ; H = 91,67%. Bi 18: C mch in nh hnh v. Ngun in c sut in ng =12V, in tr trong r = 1 . R l bin tr. a. iu chnh R cng sut mch ngoi l 11W. Tnh gi tr R tng ng. Tnh cng sut ca ngun trong trng hp ny. b. Phi iu chnh R c gi tr bao nhiu cng sut ta nhit trn R l ln nht. S: a. R = 11 ; PN = 12W v R = 1/11 ; P = 132W ; b. R = 1 Bi 19: C mch in nh hnh v. Ngun in c sut in ng = 12V, in tr trong r = 3 . in tr R1 = 12 . Hi R2 bng bao nhiu : Cng sut mch ngoi ln nht. Tnh cng sut ny. S: R2 = 4; P = 12W. Bi 20: C mch in nh hnh v. Ngun in c sut in ng = 24V, in tr trong r = 6 . in tr R1 = 4 . Hi R2 bng bao nhiu : a. Cng sut mch ngoi ln nht. Tnh Pca ngun khi . b. Cng sut trn R2 ln nht. Tnh cng sut ny. S: a. R2 = 2; PN = 48W. b. R2 = 10; P2 = 14,4W. Bi 21: C mch in nh hnh v. Ngun in c sut in in = 12Vv c in tr trong r = 0,5 . Cc in tr mch ngoi R2 = 6 , R3 = 12 . in tr R1 c gi tr thay i t 0 n v cng. in tr ampe k khng ng k. a. iu chnh R1 = 1,5 . Tm s ch ca ampe k v cng dng in qua cc in tr. Tnh cng sut ta nhit ca mch ngoi, hiu sut ca ngun in. b. iu chnh R1 c gi tr bng bao nhiu th cng sut mch ngoi t gi tr cc i. S: a. I = 2A;I1 = 2A;I2 = 4/3A; I3 = 2/3A

A

R2

,rR1 A R2 C R3 B

R4 A R5 D

, r R

, rR1 R2

, r R1 R2 , rR3 R1 R2 ,r

A R1

R2 R3

P = 22W ; H = 91,67% ; b. R1 = 4,5

Bi 22. Cho mch in nh hnh : = 6V ; r = 0,2 ; R1 = 1,6 ; R2 = 2 ; R3 = 3 . Bit RV = ; RA 0. Tnh s ch ca vn k (V) v ca ampe k (A) trong cc trng hp a) K ngt ; b) K ng. S : a) IA = 0 ; UV = 6V ; b) IA = 2A ; UV = 5,6V. Bi 23.Cho mch in nh hnh : = 6V ; r = 1 ; R1 = R4 = 1 ; R2 = R3 = 3 ; Ampe k c in tr nh khng ng k. Tnh cng dng mch chnh, hiu in th UAB v s ch ca ampe k. Ch r chiu ca dng in qua ampe k. S: I = 2,4A ; UAB = 3,6V ; IA = 1,2A c chiu t C n D. Bi 24. Cho mch in nh hnh: = 6V ; r = 1 ; R1 = R4 = 1 ; R2 = R3 = 3 ; Ampe k v kha K c in tr nh khng ng k. Tnh s ch ca ampe k khi: a) K m ; b) K ng. S: a) IA = 1A ; b) IA = 1,8A. Bi 25. Cho mch in nh hnh: Ngun in c sut in ng E v in tr trong r = 1 . Cc in tr R1 = 1 ; R2 = 4 ; R3 = 3 ; R4 = 8 . Bit UMN = 1,5V. Tm . S: = 24V. Bi 26. Cho mch in nh hnh: E = 12V, r = 1 ; n thuc loi 6V 3W ; R1 = 5 ; RV = ; RA 0 ; R2 l mt bin tr. a) Cho R2 = 6 . Tnh s ch ca ampe k, vn k. n c sng bnh thng khng ? b) Tm gi tr ca R2 n sng bnh thng. S : a) IA = 1,2A ; UV = 4,8V ; Yu hn mc bnh thng ; b) R2 = 12 ( Khi cho R2 tng th sng ca n tng). Bi 27. Cho mch in nh hnh: E = 13,5V, r = 0,6 ; R1 = 3 ; R2 l mt bin tr. n thuc loi 6V 6W. a) Cho R2 = 6 . Tm cng dng in qua n, qua R1. n c sng bnh thng khng? b) Tm R2 n sng bng thng. c) Khi cho R2 tng th sng ca n thay i nh th no? S: a) I = 0,9A ; I1 = 3,6A ; n sng yu hn mc bnh thng ; b) R2 = 4,75 ; c) Khi cho R2 tng th sng ca n gim.

V E, r A R2

K

R1

E,r R1 R2 C A A D E,rR1

R3 R3 R4

A

B

A

C K D E,r

R3

B A

R2

R4

A

R1

M

R3 R4

B

R2 A A R1 C

N E, r

B V R2

E, r

R1 R2

Bi 28. Cho mch in nh hnh: E = 15V, r = 2,4 n 1 c ghi 6v 3W, n 2 c ghi 3V 6W. a) Tnh R1 v R2, bit rng hai n u sng bnh thng. b) Tnh cng sut tiu th trn R1 v trn R2. c) C cch mc no khc hai n v hai in tr R 1, R2 (vi gi tr tnh trong cu a) cng vi ngun cho hai n vn sng bnh thng? S: a) R1 = 3 ; R2 = 6 ; b) P1 = 12W ; P2 = 1,5W ; c) (R1 nt 2)//(1 nt R2). Bi 29: C mch in nh hnh v. Ngun in c sut in ng = 12V v c in tr trong r = 0,5 . Cc in tr mch ngoi R1 = 4,5 , R2 = 4 , R3 = 3 . a. K m. Tm s ch ca ampe k , hiu in th hai u mi in tr, cng sut ta nhit ca mch ngoi, hiu sut ca ngun in. b. K ng. Tm s ch ca ampe k , hiu in th hai u mi in tr.

E, r R1 R2

A 1

C

B

2

A R1

,r K

R3

R2

CH 4. NH LUT M CHO CC LOI ON MCH MC NGUN THNH B R2 Bi 1: Cho mch in nh hnh v: Hai ngun in c: E1 = 2V, r1 = 1, E2 = 4V, r2 = 2; R1 C R1 = 5, R2 = 3, R2 = 6 R3 A a/ Tnh Eb, rb b/ in tr mch ngoi c/ cng dng in chy trong mch chnh, qua R2 S: a/ Eb = 6V; rb = 3 ; b/ RN = 7 ; c/ I = 0,6A ; I2 = 0,2A Bi 2: Cho mch in nh hnh v: Hai ngun in c: E1 = 5V, r1 = 1, E2 = 4V, r2 = 2; R1 = 8, R2 = 4, R3 = 12. Tnh: a/ in tr mch ngoi, I mch chnh, hiu in th mch ngoi. b/ Nhit lng ta ra trn R1 v R3 trong thi gian 10 pht S : RN = 6 ; I = 1A ; UAB = 6V; Q1 = 1200J; Q3 = 1800J Bi 3: Cho mch in nh hnh v: Hai ngun in c: E1 = E2 = 6 V, r1 = r2 = 2 R1 = 4, R2 = 2, R3 = 3 . Tnh Tnh cng trong mch chnh, cng sut tiu th trn R1 S : I = 0,5A ; P1 = 1/9W Bi 4: Cho mch in c s nh hnh v. Trong b ngun 6 pin ging nhau, mi pin c c sut in ng = 3V v c in tr trong r = 0,2 . Cc in tr mch ngoi R1 = 18,7 , R2 = 52 , dng in qua R1 l 0,2A a. Tnh Sut in ng v in tr trong ca b ngun. Tnh R3, tnh cng sut tiu th ca mch ngoi. b. Tnh cng sut ca mi pin, hiu sut mi pin. S:a. Eb=9V;rb= 0,3; b. R3 = 52 Bi 5. Cho mch in nh hnh v, trong E1 = 8V ; r1 = 2 ; r2 = 2 . n c ghi 6V, 6W. Xc nh gi tr ca E2 n sng bnh thng. S : E2 = 18V. Bi 6. Cho mch in nh hnh. Cho bit : E1 = 2V ; r1 = 0,1 ; E2 = 1,5V ; r2 = 0,1 ; R = 0,2 . Hy a) Hiu in th UAB. b) Cng dng in qua E1, E2 v R. S : a) UAB = 1,4V ; b) I1 = 6A (pht dng) ; I2 = 1A (pht dng) ; I = 7A. Bi 7. Cho mch in nh hnh. Cc ngun ging nhau, mi ngun c sut in ng e = 7,5V, in tr trong r = 1 ; R1 = R2 = 40 ; R3 = 20 . Tm cng dng in qua mi in tr, qua mi ngun v UCD. S : I1 = I3 = 0,24A ; I2 = 0,36A ; Ie = 0,3A ; UCD = 2,4V.A R1 R3 R2 B

B

A

R1 R3

R2

B

R1

R2 R3E1, r1 E2, r2

E1, r1 E2, r2 A R B

tnh :

C

A

R1

D

R3

B

R2

Bi 8. Cho mch in nh hnh: E1 = 12V, r1 = 1 ; E2 = 6V, r2 = 2 E3 = 9V, r3 = 3 R1 = 4 ; R2 = 2 ; R3 = 3 . a) Tm cng dng in trong mch. Ch r ngun no pht dng, ngun no ng vai tr my thu. b) Tm hiu in th UAB. S : a) I = 0,2A ; E2, E3 pht dng, E1 l my thu ; b) UAB = 4,4V.

E1, r1 A

R2

E2, r2

;R2

R2

E3, r3

B

Bi 9. Ngun in E = 24V, r = 6 c dng thp sng cc bng n. a. C 6 n 6V - 3W, phi mc cch no cc dn sng bnh thng? Cch no c li nht? b. Vi ngun trn, ta c th thp sng bnh thng ti a bao nhiu n 6V - 3W. Nu cch mc n.