Bi tp phn : Tnh in hc

Bi 1. Hai din tch im bng nhau, t trong chn khng, cch nhau mt khong r1= 2cm. Lc4 y gia chng l F1 = 1, 6.10 N.

a. Tm ln ca cc in tch b. Khong cch r2 gia chng l bao nhiu lc tc dng l F2 = 2,5.10-4 N. Bi 2. Cho hai in tch im q1 v q2 t cch nhau mt khong r = 30cm trong khng kh, lc tc dng gia chng l F0. Nu t chng trong du th lc ny b yu i 2,25 ln. Vy cn dch chng li mt khong bng bao nhiu lc tng tc gia chng vn bng F ? Bi 3. Hai in tch im t cch nahu 1 m trong khng kh th y nhau mt lc F = 1,8 N. ln in tch tng cng l 3.10-5 C. Tnh in tch mi vt. Bi 4. Hai qu cu ging nhau, mang in, t cch nhau mt on r = 20 cm, chng ht nhau mt lc F1 = 4.10-3N. Sau , cho chng tip xc v li a ra v tr c th thy chng y nhau bng mt lc F2 = 2,25.10-3 N. Hy xc nh in tch ban u ca mi qu cu. Bi . Hai in tch q1 = 4.10-8 C, q2 = -4.10-8 C t ti hai im A, B cch nhau mt khong a = 4 cm trong khng kh. Xc nh lc tc dng ln in tch im q = 2.10-9 C khi: a. q t ti trung im O ca AB. b. q t ti M sao cho AM = 4 cm, BM = 8 cm. Bi 82. Ba in tch im q1 = 27.10-8 C; q2 = 64.10-8 C, q3 = -10-7 C t ti ba nh ca tam gic ABC vung ti C. Cho AC = 30 cm; BC = 40 cm. Xc nh lc tc dng ln q3. H thng t trong khng kh. Bi 83. Hai in tch im +q v -q t ti hai im A v B cch nhau 2d trong khng kh. Xc nh lc tc dng ln in tch q0 = q t ti im M trn ng trung trc ca AB, cch AB mt on x. p dng bng s: q = 10-6 C; d = 4 cm; x = 3 cm. Bi 84. Hai qu cu c cng khi lng m = 10g, tch in q v treo vo hai dy mnh, di l = 30 cm vo cng mt im. Mt qu cu c gi c nh ti v tr cn bng, dy treo qu cu th hai lch mt gc = 600 so vi phng ng. Xc nh in tch q. Cho g = 10m/s2. Bi 85. Ngi ta treo hai qu cu nh c khi lng bng nhau m = 1g bng nhng dy c cng di l = 50 cm. Khi hai qu cu tch in bng nhau, cng du, chng y nhau v cch nhau r1 = 6cm. a. Tnh in tch mi qu cu b. Nhng c h thng vo ru c hng s in mi = 27. Tnh khong cch r2 gia 2 qu cu khi cn bng. B qua lc y Archimede. Ly g = 10m/s2. Bi 86. Hai qu cu nh ging nhau, cng khi lng m, bn knh r, in tch q c treo bng hai dy mnh c cng chiu di l vo cng mt im. Do lc tng tc Coulomb, mi dy lch 1 gc so vi phng ng. Nhng hai qu cu vo du c hng s in mi = 2 ngi ta thy gc lch ca mi dy vn l . Tnh khi lng ring D ca qu cu, bit khi lng ring ca du l D0 = 0,8.103 kg/m3. Bi 87. Cho ba in tch cng ln q t ba nh ca mt tam gic u cnh a trong khng kh. Xc nh lc tc dng ca hai in tch ln in tch th ba. Bit c mt in tch tri du vi hai in tch kia. Bi 88. Cho ba in tch cng ln q t ba nh ca mt tam gic u cnh a trong khng kh. Xc nh lc tc dng ln in tch q0 = +q ti tm O ca tam gic trong cc trng hp

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a. Cc in tch q cng du b. Mt in tch tri du vi hai in tch kia Bi 89. Hai in tch dng q1 = q v q2 = 4q t cch nhau mt on d trong khng kh. Phi t in tch q0 u, bng bao nhiu q0 nm cn bng. Bi 90. Gii li bi trn trong trng hp c ba in tch nm cn bng Bi 91. Ti ba nh ca tam gic u cnh a t ba in tch dng q. Phi t in tch q 0 u, bng bao nhiu h c 4 in tch nm cn bng. Bi 92. Bn in tch cng loi c ln q t ti 4 nh ca mt hnh vung cnh a trong khng kh. Xc nh lc tc dng ca ba in tch ln in tch th t. Bi 93. Gii li bi ton trn trong trng hp hai in tch dng, hai in tch m nm xen k nhau. Bi 94. Trong bi 92 phi t in tch q0 u h 5 in tch cn bng. Bi 95. Trong nguyn t hiro, electron chuyn ng trn u quanh ht nhn theo qu o c bn knh r = 5.10-9 cm. a. Xc nh lc ht tnh in tch gia ht nhn v electron. b. Xc nh vn tc gc ca electron (tnh ra vng/s) Bi 96. Mt in tch im Q = 10-6C t trong khng kh a. Xc nh cng in trng ti im cch in tch 30cm b. t in tch trong cht lng c hng s in mi = 16. im c cng in trng nh cu a cch in tch bao nhiu? Bi 97. Hai in tch q1 = -10-6 C, q2 = 10-6 C t ti hai im A, B cch nhau 40cm trong chn khng. Xc nh vect cng in trng ti a. M l trung im ca AB b. N c AN = 20cm; BN = 60cm. Bi 98.Ti ba nh ca tam gic vung ABC, AB = 30cm, AC = 40cm t ba in tch dng q1 = q2 = q3 = q = 10-9 C. u r Xc nh E ti chn ng cao h t nh gc vung xung cnh huyn. Bi 100. Ti ba nh A, B, C ca hnh vung cnh a trong chn khng t ba in tch dng q. Xc nh cng in trng: a. Ti tm O ca hnh vung b. Ti nh D. Bi 101. Ti ba im A, B, C trong khng kh to thnh tam gic vung ti A; AB = 4cm; AC = u r 3cm. Ti A t q1 = -2,7.10-9 C, ti B t q2. Bit E tng hp ti C c phng song song AB. Xc nh q2 v E ti C. Bi 102. Hai in tch +q v -q (q > 0) t ti hai im A, B vi AB = 2a trong khng kh. a. Xc nh cng in trng ti M nm trn trung trc ca AB, cch AB mt on x. b. Tnh x EM cc i v tnh gi tr cc i ny. Bi 103 Hai in tch q1 = 4q > 0 v q2 = - q t ti hai im A v B cch nhau 9 cm trong chn khng. Xc nh im M cng in trng tng hp ti bng 0. Bi 104

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Cho ba in tch im q1, q2, q3 t ti ba nh A, B, C ca hnh vung ABCD trong khng kh. Xc nh h thc gia q1, q2, q3 cng in trng ti D bng khng. Bi 105 Mt qu cu nh, khi lng m = 20g mang in tch q = 10 -7 C c treo bi dy mnh r trong in trng u c vect E nm ngang. Khi qu cu cn bng, dy treo hp vi phng ng mt gc = 300. Tnh ln ca cng in trng; cho g = 10 m/s2. Bi 106 Mt git cht lng tch in c khi lng 2.10-9 g nm cn bng trong in trng u c phng thng ng, c E = 1,25.105 V/m. Tnh in tch ca git cht lng v s electron tha hoc thiu trn git cht lng . Ly g = 10m/s2. Bi 107 Mt qu cu nh, bng kim loi c bn knh 1 mm t trong du. H thng t trong in r trng u, E hng thng ng t trn xung, E = 106 V/m. Tm in tch ca qu cu n nm l lng trong du. Cho khi lng ring ca kim loi v du l D = 2,7.103 kg/m3.; D0 = 800 kg/m3. Ly g = 10 m/s2. Bi 108 Mt electron trong mt in trng u thu gia tc a = 1012 m/s2. Hy tm: a. ln ca cng in trng. b. Vn tc ca electron sau khi chuyn ng c 1 s. Cho vn tc ban u bng 0. c. Cng ca lc in trng thc hin c trong s dch chuyn . d. Hiu in th gia im u v im cui ca ng i trn. Bi 109 Cho hai in tch im q1 = 10-8C; q2 = 4.10-8C t cch nhau 12 cm trong chn khng. Tnh in th ca in trng gy ra bi hai in tch trn ti im c cng in trng bng 0. Bi 110 C ba in tch im q1 = 10-8C; q2 = 2.10-8C; q3 = -3.10-8C t ti ba nh ca tam gic u ABC cnh a = 10cm trong khng kh. a. Xc nh in th ti tm O v chn ng cao H k t A. b. Tnh cng ca lc in trng khi electron di chuyn t O n H. Bi 111 u r Mt electron bay dc theo ng sc ca in trng u E vi vn tc v0 = 106 m/s v i c qung ng d = 20 cm th dng li. Tm ln ca cng in trng E. Bi 112 u r Ba im A, B, C nm trong in trng u sao cho E song song vi CA. Cho AB AC v AB = 6 cm, AC = 8 cm. a. Tnh cng in trng E, UAB v UBC Bit UCD= 100V (D l trung im ca AC). b. Tnh cng ca lc in trng khi electron di chuyn t B n C; t B n D.

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Bi 113 Hai electron rt xa nhau cng chuyn ng li gp nhau vi cng vn tc ban u v0 = 106 m/s. Hy xc nh khong cch r nh nht m hai electron c th tin li gn nhau. Bi 114 Hai in tch 9q v -q c gi cht ti hai im A, B trong chn khng (AB = d). Mt ht in tch q, khi lng m chuyn ng dc theo ng thng AB t rt xa n. Tm vn tc ban u ca ht m c th n c B. B qua tc dng ca trng trng. Bi 115 Mt electron chuyn ng vi vn tc u v0 = 4.107 m/s trn ng nm ngang v bay vo in trng ca mt t in, vung gc vi cc ng sc. Cc bn t di l = 4cm v cch nhau d = 1,6 cm. Chu U = 910V. a. Lp phng trnh qu o v xc nh dng qu o ca electron trong in trng. b. Tnh vn tc electron khi va ra khi in trng v lch so vi phng ban u. Bi 116 Cc bn ca t in phng c dng hnh ch nht, chiu rng a = 5 cm, chiu di b = 10 cm t cch nhau d = 2 cm trong khng kh. T c tch in Q = 4.10 -10C. Mt electron bay vo in u u r trng ca t vi vn tc u v0 c phng song song v dc theo chiu di ca cc bn t, cch 3d . 4 a. Hi v0 phi c gi tr ti thiu l bao nhiu electron c th bay ht chiu dai b ca bn t v bay ra khi t in trn. b. Xc nh ng nng ca electron ngay khi bay ra khi t in trn nu vn tc ban u v 0 ca electron c gi tr nh nht trn. bn tch in dng mt khong Bi 117 Mt electron bay vo khong khng gian gia hai bn kim loi tch in tri du vi vn tc v0 = 2,5.107 m/s theo hng hp vi bn tch in dng mt gc =150. di mi bn l = 5cm, khong cch gia hai bn d = 1cm. Tnh hiu in th gia hai bn, bit bng khi ra khi in trng gia hai bn t, electron chuyn ng theo hng song song vi hai bn. Bi 118 Cho ba bn kim loi phng A, B, C t song song vi nhau, tch in u, cch nhau cc khong d1 = 2,5cm; d2 = 4cm. Bit in trng gia cc bn l u, c ln E1 = 8.104 V/m; E2 = 105 V/m v c chiu nh hnh v. Ni bn A vi t (VA = 0), hy tnh cc in th VB, VC ca hai bn B, C. Bi 119 Mt t in phng khng kh, c hai bn hnh trn bn knh R = 6cm t cch nhau d = 0,5 cm. t vo hai bn mt hiu in th U = 10V. Hy tnh: in dng ca t, in tch ca t, nng lng ca t.

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Bi 120 Mt t phng khng kh c in dung C0 = 0,1 F c tch in n hiu in th U = 100V. a. Tnh in tch Q ca t b. Ngt t khi ngun. Nhng t vo in mi lng c = 4. Tnh in dung, in tch v hiu in th ca t lc ny. c. Vn ni t vi ngun ri nhng vo in mi lng trn. Tnh nh cu b. Bi 121 a. Tnh in dung ca t in phng khng kh c in tch mi bn S = 100cm2, khong cch gia hai bn d = 2mm. b. Nu a vo gia hai bn lp in mi dy d=1mm ( = 3) th in dung ca t l bao nhiu? Bi 122 Thay lp in mi bng bn kim loi c cng b dy. Tnh in dung ca t lc ny. in dung ca t c ph thuc vo v tr lp in mi hoc bn kim loi khng? Bi 123 Mt t in phng vi in mi l khng kh, c hai bn cch nhau l d, mi bn c din tch l S. S d Ngi ta a vo mt lp in mi c din tch , c b dy v c hng s in mi 2 2 = 4 (nh hnh) in dung ca t in tng ln hay gim i bao nhiu ln so vi khi cha c in mi. Bi 124 T phng khng kh c in dung c = 1nF c tch in n hiu in th U = 500V. a. Tnh in tch Q ca t. b. Ngt t khi ngun, a hai bn t ra xa khong cch tng gp 2. Tnh C 1, Q1, U1 ca t. c. Vn ni t vi ngun, a hai bn t ra xa nh trn. Tnh C2, Q2, U2. Bi 125 Mt t in phng c din tch mi bn S = 56,25 cm2, khong cch gia hai bn d = 1cm. a. Tnh in dung ca t in khi t t trong khng kh. b. Nhng t vo in mi lng c hng s in mi =8 sao cho in mi ngp phn na t. Tnh in dung, in tch vo hiu in th gia hai bn t khi: + T vn c ni vi hiu in th U = 12V. + T tch in vi hiu in th U = 12V, sau ngt khi ngun ri nhng vo in mi. Bi 126 Cho cc t in: C1 = 10 F; C2 = 6 F; C3 = 4 F c mc vo hiu in th U = 24V nh hnh. Hy tm in dung ca b t, in tch v hiu in th trn mi t.

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Bi 127 Cho b t nh hnh Bit C1 = C2 = 6 F; C3 = C4 = 3 F; U = 12V. Hy tnh in dung b t, in tch v hiu in th trn mi t. Bi 128 Tnh in dung ca b t, in tch mi t. Bit C1 = 2 F ; C2 = 4 F; C3 = C4 = 6 F; U = 20V. Bi 129 Cho 4 t mc vi nhau nh hnh. Khi dng hai cht 1, 2 hoc hai cht 1, 3 th in dung c b vn khng i. Tm h thc h gia cc in dung ca cc t. Bi 130 T xoay gm 30 bn, mi bn c dng na hnh trn bn knh R = 5cm, khong cch gia hai bn lin tip d = 1mm. Phn din tch i din gia hai bn c dng hnh qut m gc tm l . Tnh in dung ca t khi gc tm l . T suy ra gi tr in dung ln nht ca t c th c. Cho in mi l khng kh. Bi 131 Bn tm kim loi phng ging nhau, t song song cch u nhau nh hnh. Ni A, C vi nhay ri ni B, D vi ngun U = 12V. Sau ngt ngun. Tm hiu in th gia B, D nu sau : a. Ni A vi B bng dy dn. b. Khng ni A, B nhng lp y khong gia B, D bng in mi c =4. Bi 132 Cho mch t nh hnh v Bit C1 = 1 F ; C2 = 4 F; C3 = 2 F, C4 = 3 F; C5 = 6 F; UAB = 12V. Hy tnh a. in dung ca b t b. in tch v hiu in th mi t Bi 133 Cho b t c mc nh hnh. Bit cc t c in dung bng nhau a. Cho UAB = 88V, tnh UMN, UPQ. b. Bit UMN = 5,5V, tnh UAB, UPQ. Bi 134 Cho mch in nh hnh v Bit C1 = 1 F ; C2 = 3 F; C3 = 2 F, U = 12V. Tnh UMN khi a. C4 = 6 F b. C4 = 2 F Bi 135

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Cc t ging nhay c mc nh s . in dung mi t l C0. a. Tm in dung ca b t. b. Tm in tch trn t C3 bit C0 = 1 F; UAB = 12V. Bi 136 C mt s t ging nhau, mi t c in dung C0 = 2 F. Hy tm s t ti thiu v cch mc din dung ca b t l a. 3,2 F b. 1,2 F Bi 137 Cho mch t nh hnh v Bit C1 = 2 F ; C2 = 10 F; C3 = 5 F; U2 = 10V. Tnh in tch v hiu in th trn mi t. Bi 138 Ba t in nh nhau c mc vo mch nh hnh v. Bit U1 = 3V, U2 = 1,5 V. Hy tnh UAB, UBO v UCO. Bi 139 T in C1 = 2 F c tch in n hiu in th U1 = 300V; t C2 = 3 F tch in n hiu in th U2 = 400V. a. Ni hai bn tch in cng du vi nhau. b. Ni hai bn tch in tri du vi nhau. Bi 140 Cho mch t nh hnh v Bit C1 = 1 F ; C2 = 3 F; C3 = 4 F; C4 = 2 F; U = 24V. a. Tnh in tch cc t khi K m. b. Tm in lng qua kho K khi K ng. Bi 141 Cho mch in nh hnh v Bit U1 = 12V; U2 = 24V; C1 = 1 F; C2 = 3 F. Lc u kho K m. a. Tnh in tch v hiu in th trn mi t b. Kho K ng li. Tnh in lng qua kho K. c. Sau ta li m kho K. Tnh in tch trn cc t lc ny. Bi 142 Cho mch in nh hnh Bit C1 = 2 F ; C2 = 6 F; C3 = 4 F; U = 40V. Ban u K m, cc t cha tch in. a. Tm in tch v hiu in th cc t b. K chuyn sang v tr 2. Tm in tch v hiu in th trn cc t lc ny. Bi 143

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Cho mch t nh hnh v. Bit C1 = 0,5 F ; C2 = 1 F; U1 = 5V; U2 = 40V. a. ng K vo (1), tnh in tch mi t. b. Chuyn K sang (2), tnh in tch v hiu in th mi t. Ngay sau khi K ng vo (2), in lng chuyn qua K bng bao nhiu? Theo chiu no? Bi 144 Cho ba t mc nh s . Bit C1 = 4 F; hiu in th gii hn 1000V; C2 = 2 F, hiu in th gii hn 500V; C3 = 3 F, hiu in th gii hn 300V. a. Tm hiu in th hai u A, B cn mc vo b t khng b hng. b. Gi UAB c gi tr ln nht. Sau khi ngt b t b ra khi ngun ngi ta ct mch ti ri em ni u vi A, u B li ni vo ch ct. Tm in tch v hiu in th trn cc t lc ny. Bi 145 Cho mch in nh hnh v. Bit C1 = C2 = 2 F; C3 = 4 F; UAB = 12V. Ban u cc t cha tch in v kho K v tr 1. a. Tnh in tch trn cc t. b. Sau , kho K chuyn sang v tr 2. Tm hiu in th trn cc t lc ny. Bi 146 Cho mch t nh hnh v. Bit C1 = 1 F; C2 = 3 F; U = 24V. Tnh hiu in th mi t khi a. Ban u K 1 sau chuyn sang 2. b. Ban u K 2 sau chuyn sang 1 ri li chuyn v 2. Bi 147 Cho mch in nh hnh v. Cc t c in dung C = 2 F; U = 20V. Ban u K 1. Sau K chuyn t v tr 1 sang 3. Tm in tch trn mi t. Bi 148 Bn t: C1 = C3 = 2C0, C2 = C4 = C0. Ban u mc A, B vo hiu in th U = 60V (hnh). Tnh UMN. Sau ngt A, B ra khi ngun ri ni hai im M, N vo ngun trn sao cho UM > UN. Tnh UAB Bi 149 Hai t c in dung C1 = 1 F; C2 = 3 F; ln lt c tch in n hiu in th U1 = 100V, U2 = 200V. Sau ni hai bn cng du li vi nhau. Tnh hiu in th mi t v nng lng ta ra di dng nhit. Bi 150 Hai t in C1 = 2 F; C2 = 0,5 F, c mt bn ni t. Hiu in th gia cc bn pha trn v t ln lt l U1 = 100V, U2 = -50V. Tnh nhit lng ta ra khi ni cc bn pha trn ca hai t bng dy dn. Bi 151

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C bn bng n mc theo s mch in nh hnh v. Hi bng no sng, bng no khng sng khi: a. k1 cht 1, k2 cht 3. b. k1 cht 1, k2 cht 4. c. k1 cht 1, k2 cht 5. d. k1 cht 2, k2 cht 3. e. k1 cht 2, k2 cht 4. f. k1 cht 2, k2 cht 5. Bi 152 C ba bng n 1, 2, 3 cng loi , mt s dy dn in, mt ngun in v mt kha k. Hy v cc s mch in tha mn hai iu kin: a. k ng, ba n u sng. b. k m, ch c hai n 1 v 2 sng, n 3 khng sng Bi 153 C ba bng n 1, 2, 3, mt s dy dn in v mt ngun i. Hy v cc s mch in m khi tho bt mt bng n ra th hai bng cn li vn c th sng. Ch r bng c tho ra trong tng s Bi 154 Cho mt ngun in (b pin), 1 vn k, 1 ampe k, 2 bng n 1 v 2, hai kho k1 v k2 v mt s dy dn. Hy v mt s mch in tho mn cc iu kin sau: a. k1 ng, k2 m: Ampe k ch cng dng in qua n 1 cn n 2 khng sng. b. k1 m, k2 ng: Ampe k ch cng dng in qua n 2 cn n 1 khng sng. c. k1 v k2 u ng: Ampe k ch cng dng in tng cng qua c 2 n v 2 n u sng. (Trong cc trng hp a, b, c vn k u ch hiu in th hai u ngun) Bi 155 Trong thi gian 2 pht, s electron t do dch chuyn qua tit din thng ca vt dn l 37,5.1019 electron. Hi: a. in lng chuyn qua tit din thng ca vt dn trn. b. Cng dng in qua vt dn bng bao nhiu? c. cng dng in qua vt dn tng gp i th trong thi gian 3 pht, in lng chuyn qua vt dn bao nhiu? Bi 156 Vi phn na thi gian, in lng chuyn qua tit din thng ca on mch th nht bng 2 in lng chuyn qua tit din thng ca on mch th hai. Tnh in lng chuyn qua tit 3 din thng ca on mch th hai trong thi gian 5 pht. Bit cng dng in qua mch th nht l 4 A. 3

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Bi 157 Mt dy dn di 100m, tit din 0,28mm2 t gia hai im c hiu in th l 12V th cng dng in qua dy dn l 1,2A. Hi nu thay dy dn trn bng mt dy dn khc cng cht vi dy dn trn, di 25m, in tr 2,8 th dy dn ny c tit din l bao nhiu ? Cng dng in qua n l bao nhiu ? Bi 158 Mt dy ng h c in tr R. Ko gin u cho di ca dy tng ln gp i (nhng th tch ca dy khng i). Hi in tr ca dy sau khi c ko ? Bi 159 Tnh in tr tng ng ca on mch sau. Bit cc in tr bng nhau v bng r. Bi 160 C ba in tr ging nhau v bng r. Hi c bao nhiu cch mc cc in tr ny vi nhau ? Tnh in tr tng ng trong cc trng hp. Bi 161 C mt s in tr r = 5 . Hi phi dng ti thiu bao nhiu in tr r mc thnh mch c in tr tng ng R = 3 . Bi 162 Cho mch in nh hnh v: R1 = 10 ; R2 = 8 ; R3 = 6 ; U = 12V. Tnh: 1. Cng dng in qua mi in tr 2. Hiu in th gia

a. Hai u mi in tr b. Hai im A v N c. Hai im M v BBi 163 Cho mch in nh hnh v R 1 = R2 = 6 ; R 3 = 8 ; R 4 = 4 . Hiu in th gia hai im M v B l UMB = 12V. Tnh:

1. Hiu in th gia hai u R1. 2. Hiu in th gia hai u mch.

Bi 164 Mt mch in gm in tr R1 mc ni tip vi in tr R2 = 9 . Hiu in th hai u R1 v hai u mch ln lt l U = 12V. Tnh in tr R1. Bi 165

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C mch in nh hnh v: R1 = 5 ; R2 = 10 ; U = 18V; cng dng in qua R2 l 1A. Tnh R3. Bi 166 Cho mch in nh hnh v R1 = 6 ; R2 = 4 ; R3 = 12 ; U = 12V. in tr ampe k l Ra khng ng k (Ra 0). Tm s ch ca ampe k A. Bi 167 C hai in tr R1 v R2 mc song song gia hai im c hiu in th U = 6V. Dng am pe k c in tr khng ng k o c cng dng in qua R1 l 0,5A v qua mch chnh l 0,8A. Tnh R1 v R2. Bi 168 Mc hai in tr R1 v R2 vo hiu in th U = 6V. Khi chng mc ni tip nhau th cng dng in qua chng l 0,24A. Khi chng mc song song cng dng in tng cng qua chng l 1A. Tnh R1 v R2. Bi 169 Cho mch in nh hnh v U = 18V, cc in tr ca cc ampe k khng ng k. in tr R3 c th thay i c. S ch cc ampe k A1, A2 theo th t l 0,5A; 0,3A. 1. Tnh R1 v R2. 2. Chnh R3 s ch A l 1A. Tnh R3 tng ng. 3. Gim gi tr R3 so vi cu 2 th s ch cc ampe k thay i nh th no Bi 170 Cho mch in nh hnh v U = 12V; R1 = 6 ; R2 = 3 ; R3 = 6 . in tr ca cc kho v ca ampe k A khng ng k. Tm cng dng in qua cc in tr v tnh cng sut ca mch khi:

1. k1 ng, k2 m 2. k1 m, k2 ng 3. k1 v k2 u ngBi 171 Cho mch in nh hnh v: U = 18V; R1 = 12 ; R2 = 6 ; R3 = 12V. Cc ampe k c in tr khng ng k. Tm s ch ca cc ampe k. Bi 172 Cho mch in nh hnh v: U = 12V; R1 = R2 = 10 ; R3 = 5 ; R4 = 6 . Tnh cng dng in qua mi in tr v hiu in th hai u mi in tr Bi 173 Cho mch in nh hnh v:

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U = 12V; R1 = 24 ; R3 = 3,8 ; ampe k A c in tr Ra = 0,2 . Ampe k A ch 1A. Tnh:

1. in tr R2. 2. Nhit lng to ea trn R2 trong thi gian 5 pht. 3. Cng sut ca in tr R2.Bi 174 Cho mch in nh hnh v: R1 = R2 = R3 = 5 ; R5 = 6 ; U = 24V. Cng sut nhit trn R3 l 7,2W. Tnh cng sut nhit trn R4. Bi 175 Cho mch in nh hnh v: U = 6V; R1 = 6 ; R3 = 4 . Cng dng in qua R2 l I1 = Bi 176 Cho mch in nh hnh v: R1 = 10 ; R2 = 6 R 7 = R3 = 2 ; R 4 = 1 R5 = 4 ; R6 = 2 U = 24V Tnh cng dng in qua mi in tr. Bi 177 Cho mch in nh hnh v: R1 = 12 ; R2 = 16 ; R3 = 4 ; R4 = 14 ; R5 = 8 ; U = 12V. in tr ca cc ampe k v ca dy ni khng ng k. Tnh s ch ca cc ampe k trong cc trng hp: 1. k1 m; k2 ng. 1. k1 ng; k2 m. 3. k1, k2 u m. Bi 178 Cho mch in nh hnh v R1 = 8 ; R2 = 3 ; R3 = 5 ; R4 = 4 ; R5 = 6 ; R6 = 12 ; R7 = 24 ; cng dng in mch chnh l I = 1A. Tnh hiu in th U hai u mch v hiu in th hai u in tr R3. Bi 179 R1 = 4,8 ; R2 = 12 ; R3 = 3 ; R4 = 2 ; U = 6V. Tnh in tr tng ng ca mch, cng dng in qua mi in tr v hiu in th hai u mi in tr khi: 2 A. Tnh R2? 3

1. 2. 3. 4.

k1 ng, k2 m. k1 m, k2 ng. k1, k2 u ng. k1, k2 u m.

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B qua in tr ca cc dy ni v cc kho k. Bi 180 Cho mch in nh hnh v: U = 6V; R1 = 3 . Khi k m, ampe k A1 ch 1,2A. Khi k ng ampe k A2 ch 0,5A. Tnh R2 v R3. B qua in tr ca cc ampe k v kho k. Bi 181 Mt bng n c in tr R1 = 12 , chu c cng dng in ln nht l 0,5A. n mc ni tip vi mt bin tr. t vo hai u mch mt hiu in th U. 1. Hy v s mch in 2. Khi in tr ca bin tr tham gia vo mch l R0 = 24 th cng dng in qua n ln nht. Tnh hiu in th U. Bi 182 Mch in gm mt bin tr mc ni tip vi mt in tr R0. t vo hai u mch mt hiu in th U. iu chnh con chy in tr ca bin tr tham gia vo mch l R 1 = 10 th o c hiu in th hai u bin tr l U1 = 5V, nu l R2 = 40 th hiu in th hai u bin tr l U2 = 10V. Tnh U v R0. Bi 183 Cho mch in nh hnh v R1 = 3 , R2 = 2 ; R4 = 1 ; R5 = 4 ; U = 18V.

1. Khi k m, ampe k A ch 1,8A. Tnh R3. 2. Khi k ng, tnh:- Cng dng in qua mi in tr. - Hiu in th gia M, N; gia M, C. B qua in tr ca ampe k v kho k. Bi 184 Cho mch in nh hnh v: * Nu t vo A, B mt hiu in th UAB = 120V th cng dng in qua R2 l I2 = 2A v hiu in th hai u C, D l UCD = 30V. * Nu t vo C, D mt hiu in th UCD = 120V th hiu in th hai u A, B l UAB = 20V. Tnh R0, R1, R2. Bi 185 C mch in nh hnh v sau: Cho R1 = R4 = 3 ; R2 = 2 ; R3 = 4 . in tr cc dy ni v cc kha khng ng k. Tnh in tr tng ng ca mch khi: 1. k1 m; k2 v k3 ng 2. k2 m; k1 v k3 ng 3. k3 m; k1 v k2 ng

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4. k1 v k2 m; k3 ng 5. k1 v k3 m; k2 ng 6. k2 v k3 m; k1 ng 7. k1, k2, k3 u ng. Bi 186 Cho mch in nh hnh v R1 = 4 ; R2 = 6 ; R3 = 12 ; U = 6V. in tr ca cc ampe k v dy ni khng ng k. Tnh s ch ca cc ampe k khi: 1. k1 m; k2 ng 2. k1 ng; k2 m 3. k1; k2 u m 4. k1; k2 u ng Bi 187 C mch in nh sau: R1 = R3 = 12 ; R2 = R4 = 6 ; U = 12V. B qua in tr cc dy ni v cc kho k. Tnh in tr tng ng v cng dng in qua mi in tr khi: a. k1 ng, k2 m c. k1, k2 u m b. k1 m, k2 ng d. k1, k2 u ng. Bi 188 Cho mch in nh hnh v R1 = 6 ; R2 = 4 ; R3 = 12 ; R4 = 7 ; U = 12V. B qua in tr ca cc kho k. Tnh cng dng in qua mi in tr khi: 1. k1, k2 m; k3, k4 ng. 2. k1, k3 m; k2, k4 ng. 3. k1, k4 m; k3, k2 ng. 4. k3, k2 m; k1, k4 ng. 5. k4, k2 m; k3, k1 ng. 6. k1 m; k2 k3, k4 ng. 7. k2 m; k1, k3, k4 ng. 8. k3 m; k1 k2, k4 ng. 9. k4 m; k1 k2, k3 ng. Bi 189 Cho mch in nh hnh v: U = 12V, b qua in tr ca cc ampe k v cc kho. 1. k1 m, k2 ng, ampe k A2 ch 0,2A. Tnh R1. 2. k1 ng, k2 m, ampe k A1 ch 0,3A. Tnh R3. 3. k1, k2 u ng, ampe k A ch 0,6A. Tnh R2 v s ch ca ampe k A1 v ampe k A2. 4. Thay i in tr no th s ch ng thi ca ba ampe k u thay i khi k1 v k2 u ng. Bi 190

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Cho mch in nh hnh v: U = 12V; R1 = 12 ; R3 = 4 ; R4 = 8 ; R5 = 15 . Ampe k A c in tr Ra = 1 . B qua in tr ca kho k. 1. Khi k m, ampe k A ch 0,5A. Tnh R2. 2. Tm s ch ampe k v cng dng in qua kho k (ch r chiu dng in qua kho k) khi k ng. Bi 191 Cho mch in nh hnh v U = 12V; R1 = 20 ; R2 = 5 ; R3 = 8 . C mt vn k V c in tr rt ln v mt ampe k A c in tr rt nh. 1. Tm s ch ca vn k V khi n mc gia A v N trong hai trng hp k m v k ng. 2. Thay vn k V bng ampe k A. Hi nh cu 1. Bi 192 Dng in chy qua mt vng dy dn ti hai im A,B. Si dy dn to nn vng dy l mt si dy kim loi, ng nht, tit din u, c chiu di l. Xc nh v tr A v B in tr ca vng dy nh hn in tr si dy n ln. Bi 193 Cho mch in nh hnh v U = 12V; R1 = 6 ; R2 = 6 ; R3 = 12 ; R4 = 6 . 1. Tnh cng dng in qua mi in tr v hiu in th gia hai u mi in tr. 2. Ni M v N bng mt vn k V (c in tr rt ln) th vn k ch bao nhiu? Cc dng ca vn k c ni vi im no? 3. Ni M v N bng mt ampe k A (c in tr khng ng k) th ampe k ch bao nhiu? Bi 194 Cho mch in nh hnh v C mt vn k V c in tr rt ln v mt ampe k A c in tr rt nh. R1 = 6 ; R2 = 3 ; R3 = 12 ; R4 = 6 ; R5 = 6 ; U = 12V. 1. Ni vn k gia C v D th vn k ch bao nhiu ? 2. Ni vn k gia D v E th vn k ch bao nhiu ?

3. Ni ampe k gia C v D th ampe k ch bao nhiu ? 4. Ni ampe k gia D v E th ampe k ch bao nhiu ?Bi 195 Cho mch in nh hnh v: R1 = 8 ; R2 = 4 ; R3 = 2 ; U = 12V Khi kha k ng, ampe k ch 0. Tnh in tr R4 v cng dng in qua mi in tr. B qua in tr ca ampe k v ca kha k. Bi 196 R 1 = R3 = R 4 = R5 = 6 ;

R2 = 12 , R6 = 4 ;

R7 = 2 ; U = 12V

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B qua in tr ca ampe k v kha k. Tnh s ch ca ampe k khi:

1. k m. 2. k ng.Bi 197 Cho mch in nh hnh v: R1 = 15 ; R2 = 10 ; R3 = 12 U = 12V. B qua in tr ca ampe k. 1. Cho R4 = 12 . Tnh cng dng in v ch r chiu dng in qua ampe k. 2. Hi nh cu 1 nhng cho R4 = 8 . 3. Tnh R4 khi cho dng in qua ampe k c chiu t C n D v c cng l 0,2A. Bi 198 Cho mch in nh hnh v: R1 = 8 ; R2 = 4 ; R3 = 6 U = 12V Vn k c in tr rt ln, in tr kha k khng ng k.

1. Khi k m, vn k ch bao nhiu ? 2. Cho R4 = 4 . Khi k ng, vn k ch bao nhiu ? 3. k ng, vn k ch 2 V. Tnh R4Bi 199 Cho mch in nh hnh v: B qua in tr ca cc ampe k v kha k. 3 Khi k m, ampe k A1 ch A. . 4 2 1 Khi k ng, ampe k A1 ch A , ampe k A2 ch A. 3 3 Tnh R1, R2, R3. Bit U = 12V. Bi 200 Cho mch in nh hnh v: U = 90V; R1 = 45 ; R2 = 90 ; R4 = 15 ; B qua in tr ca ampe k v ca kha k. Khi k m hoc k ng th s ch ca ampe k A khng i. Tnh s ch ca ampe k A v cng dng in qua kha k khi k ng. Bi 201 Cho mch in nh hnh v: Mc vn k V gia hai im A v B th vn k ch 12V, mc vn k gia hai u R1 th vn k ch 4V, mc vn k gia hai u R2 vn k ch 6V. Hi khi khng mc vn k th hiu in th hai u R1, hai u R2 l bao nhiu ? Bit vn k c in tr l RV. Bi 202

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Cho mch in nh hnh v: 4 in tr u ging nhau. Hiu in th gia A v B lun khng i v l U = 120V. Mc mt vn k V (c in tr Rv) vo hai im A, E th vn k ch 60V. Tm s ch ca vn k khi mc vn k vo hai im: 1. A, D; 2. A, C. Bi 203 Cho mch in nh hnh v: R1 = R4 = 4 ; R2 = 2 ; R3 = 8 ; R5 = 10 ; U = 12V. in tr ca cc dy ni v kha k khng ng k. Tnh cng dng in qua mi in tr khi: 1. k m; 2. k ng. Bi 204 Cho mch in nh hnh v: R1 = R3 = R4 = 4 ; R2 = 2 ; U = 6V. 1. Khi ni gia A v D mt vn k th vn k ch bao nhiu ? Bit in tr vn k rt ln. 2. Khi ni gia A v D mt ampe k th ampe k ch bao nhiu ? Bit in tr ca ampe k rt nh. Tnh in tr tng ng ca mch trong trng hp ny. Bi 205 Cho mch in nh hnh v: R1 = R2 = R3 = R4 = 10 ; U = 12V. 1. Tnh cng dng in qua mi in tr v cng dng in mch chnh. 2. Ni hai im C, B bng mt vn k (c in tr rt ln) th vn k ch bao nhiu ? 3. Ni hai im C, B bng mt ampe k (c in tr rt nh) th ampe k ch bao nhiu ?

Bi 206 Cho mch in nh hnh v: R 1 = 4 ; R 2 = R4 = 6 . 1. Khi k m, cng dng in qua R1 ln gp 2 ln cng dng in qua R2. Tnh R3. 2. ng kha k. Tnh cng dng in qua mi in tr v qua kha k. Cho U = 7,8V. B qua in tr ca kha k. Bi 207 Cho mch in nh hnh v: R 1 = 2 ; R 2 = 2 ; = R3 = 1 . R4 = 6 ; R5 = 3 ; U = 7,2V B qua in tr ca kha k. Tnh cng dng in qua mi in tr khi: 1. k m; 2. k ng. Bi 208 R1 = 600 ; R2 = 500 ; Vn k c in tr Rv = 2000 ; kha k c in tr khng ng k, U = 100V. Tm s ch ca vn k khi:

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1. k m;

2. k ng.

Bi 209 C hai in tr R1 v R2 mc gia hai im c hiu in th U = 12V. Khi R1 ghp ni tip vi R2 th cng sut ca mch l 4W. Khi R1 ghp song song vi R2 th cng sut ca mch l 18W. Tnh R1 v R2. Bi 210 Mt gia nh c hai n loi 220V - 40W, 220V - 100W v mt bp in loi 220V 1000W. Ngun in s dng c hiu in th n nh l 220V. 1. Cho bit ngha cc s liu ghi trn mi dng c. 2. Cch mc cc dng c trn vo mch in. 3. Tnh in tr mi dng c. 4. Trong 1 ngy m, cc n dng trung bnh 5 gi, bp in dng hai gi. Tnh in nng tiu th v s tin in phi tr trong 1 thng (30 ngy). Bit 1 kWh in gi 450 ng. Bi 211 Mt bng n c ghi 120V - 60W c s dng vi mng in c hiu in th 220V. 1. Cn phi mc in tr R vi n ra sao n sng bnh thng. Tnh gi tr ca in tr R. 2. Tm hiu sut ca cch s dng trn. Bi 212 Cho hai n 1: 120V - 40W; 2: 120V - 60W. Tm cng qua n v sng mi n trong hai trng hp ? n no sng hn ? 1. Mc hai n song song vo mng in c hiu in th 120V. 2. Mc ni tip hai n vo mng in c hiu in th 240V. Bi 213 Mt m in c ghi 120V - 480W. 1. Tnh in tr ca m v dng in qua m khi dng in c hiu in th 120V. 2. Dng m trn un si 1,2 lt nc 20 0C. Tm thi gian un si lng nc trn bit hiu sut ca m l 70%, cho C = 4200 J/kg.K. Bi 214 Mt bp in mc vo mch in c hiu in th 110V th cng dng in qua bp l 4A. 1. Tnh in tr ca bp. 2. Tnh cng sut ca bp v nhit lng bp to ra trong 30 pht. 3. Nu ct ngn dy in tr i mt na v vn mc vo hiu in th trn th cng sut ca bp so vi lc cha ct ra sao? 4. Nu ct i dy in tr ri chp li hai u ( mc song song ) v vn mc vo hiu in th trn, cng sut ca bp lc ny ra sao?

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Bi 215 Mt gia nh s dng hai n loi 120V - 60W v mt bp loi 120V - 600W. 1. Cch mc n vo mng in chng hot ng bnh thng? Bit hiu in th mng in c gi khng i l 120V. 2. Cng dng in qua n v qua dy dn chnh gi cao im (s dng ht cc dng c). 3. Bit n dng 5 gi, bp dng hai gi trong 1 ngy m. Tnh in nng tiu th v tin in phi tr trong 1 thng (30 ngy). Gi 1KWh l 450. Bi 216 Cho mt bp in gm hai dy in tr: R1loai 220V - 400W; R2 loi 220V - 600W mc nh s . Trong A, B v C,D l hai cm dng ni tip vi mch in. 1. Tm in tr mi dy khi chng hot ng ng cng sut. 2. Tm cng sut ca bp trong cc trng hp: + Ni AB vi mch in 220V. + Ni CD vi mch in 220V. + Ni C vi D bng dy dn ri ni AB vi mch in 220V. + Ni A v B bng dy dn ri ni CD vi mch in 220V. Bi 217 Mt in tr lm bng dy Niklin cun thnh 100 vng trn mt li s hnh tr ng knh D = 4 cm. Bit ng knh dy in tr d= 0,1 mm v in tr sut ca n 20 C l p = 4.10 m. 1.Tnh in tr ng dy 20 C. 2.Tnh in tr ca ng dy 120 C, bit h s nhit in tr ca Niklin l 4.10 k . Suy ra in tr sut ca Niklin 100 C. Bi 218 Gia hai im c hiu in th U = 220V ngi ta mc dy song song hai dy kim loi. Cng dng in qua dy th nht l I1 = 4A v qua dy th hai l I2 = 2A. 1. Tnh cng sut ca mch trn. 2. cng sut ca mch l 2000W ngi ta phi ct b mt on ca dy th hai ri li mc nh c. Tnh in tr phn dy b ct b. Bi 219 Mt bp in c 2 in tr: R1= 4 v R2= 6 . Nu bp ch dng in tr R1 th un si mt m nc trong 10 pht. Tnh thi gian cn thit un si m nc trn (mng in c hiu in th khng i). 1. Ch dng R2. 2. Dng R1 ni tip R2. 3.Dng R1 song song R2. (Bit khng c s mt nhit ra mi trng) Bi 220 n : 120V - 100 W c mc vi mng in c hiu in th khng i U = 120V. in tr tng cng t mng in n ni tiu th l rd = 6 .

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1. Tm cng dng in qua n; hiu in th hai u n v cng sut ca n. 2. Nu mc thm mt bp in loi 120V - 1000W song song vi n th sng ca n by gi ra sao? Cng xut n lc ny? Bi 221 mc n vo ngun in th ln hn gi tr ghi trn n, c th dng mt trong hai s bn. Bit c hai trng trng hp n u sng bnh thng. S no c hiu sut ln hn.

Bi 222 Dng bp in un nc. Nu ni bp vi U1 = 120V th thi gian nc si l t2 = 20 pht. Hi nu ni bp vi U3 = 60V th nc si sau thi gian t3 bao lu ? Cho nhit lng hao ph t l vi thi gian un nc. Bi 223 C 4 n gm: 1 n 1 loi 120V - 40W; 1 n 2 loi 120V - 60W; 2 n 3 loi 120V 50W. 1. Cn mc chng nh th no vo mng in c hiu in th 240V chng sng bnh thng? V s mch in. 2. Nu 1 n b t dy tc, sng cc n cn li s thay i ra sao? Bi 224 Mt n c ghi 24V - 12W. s dng vo hiu in th 120V ngi ta mc n vi bin tr R theo hai s sau. Bit bin tr R c gi tr ti a l 200 1. Tm v tr con chy C mi s . 2. Hiu sut ca mi cch s dng trn? Bi 225 C hai n loi 1: 120V-100W; 2: 120V-60W. s dng chng vo mng in 240V sao cho chng sng bnh thng, ngi ta mc chng theo hai s sau: 1. Tm r1 v r2. 2. Hiu sut s dng in trong mi cch mc trn. Bi 226 Cho mch in nh hnh v, gi tr ton phn ca bin tr l R = 1000 , vn k V1 c in tr R1 = 600 , ca V2 c R2 = 1200 . Hiu in th hai u mch l U = 180V. 1. Xc nh s ch trn mi vn k khi C v tr sao cho RAC = 400 . 2. Xc nh v tr ca C s ch trn 2 vn k bng nhau. Bi 227 Bp in c ghi 220V - 800W c ni vi hiu in th 220V c dng un si 2 lt nc t 200C. Bit hiu sut s dng bp l H = 80% v nhit dung ring ca nc C = 4200 J/kg.. 1. Tm thi gian un si nc v in nng tiu th ra kWh.

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2. Bit dy in tr c ng knh d = 0,2 mm, in tr sut =5.10-7 m c qun trn mt li s cch in hnh tr c ng knh D = 2cm. Tnh s vng dy ca bp in trn. Bi 228 Cu ch trong mch in c tit din S = 0,1 mm2, nhit 270C. Bit rng khi on mch th cng dng in qua dy ch l I = 10A. Hi sau bao lu th dy ch t? B qua s to nhit ra mi trng xung quanh v s thay i ca in tr, kch thc dy ch theo nhit . Cho bit nhit dung ring, in tr sut, khi lng ring, nhit nng chy v nhit nng chy ca ch ln lt l: C = 120 J/kg ; = 0,22.10-6 m; D = 11300 kg/m3; = 25.000 J/kg; t0 = 3270C. Bi 229 Mt bn l c ghi 120V - 1000W. Khi mc bn l vo mch in th hiu in th trn cm in gim t U1 = 125V xung U2 = 100V. 1. Xc nh in tr cc dy ni (coi in tr bn l khng thay i theo nhit ). 2. Thc t, in tr ca bn l b thay i theo nhit v cng sut tiu th thc t ca bn l P = 650W. Tnh hiu in th gia hai u cm in lc ny v in tr P ca bn l khi . Bi 230 Khi mc mt bp in vo hiu in th U1 = 120V th nc trong m s si sau thi gian t1 = 10 pht. Nu mc bp vo hiu in th U2 = 110V th thi gian cn thit un si lng nc trn l t2 = 15 pht. Tnh vo hiu in th U3 = 100V. Lng nc trong n v nhit bn u ca nc trong cc trng hp l nh nhau. Cho bit nhit lng to ra mi trng xung quanh t l vi thi gian un nc. Bi 231 Mt cu ch c ng knh dy ch d1 = 0,5 mm s chy ra khi dng in qua n I1 5A trong mt thi gian. Hi vi dy ch c ng knh d2 = 1mm s chu c dng in ln nht l bao nhiu? Coi nhit lng to ra mi trng xung quanh t l thun vi din tch xung quanh ca dy ch. B qua s mt nhit do tip xc. Bi 232 Khi c dng in I1 = 1A i qua mt dy dn trong mt khong thi gian th dy nng ln n nhit t1 = 400C. Khi dng in I2 = 2A i qua th n nng ln n nhit t2 = 1000C. Hi khi dng in I3 = 4A i qua th n nng ln n nhit t3 l bao nhiu? Coi nhit mi trng xung quanh v in tr dy dn l khng i. Bit nhit lng to ra mi trng xung quanh t l thun vi chnh lch nhit gia dy dn v mi trng xung quanh. Bi 233 Tm r1, r2, r3 theo R1, R2, R3 mch hnh sao tng ng mch hnh tam gic. Bi 234 Tm r1, r2, r3 theo R1, R2, R3 mch hnh tam gic tng ng mch hnh sao. Bi 235 Cho mch in nh hnh v

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R1 = R2 = R3 = 14 ; R4 = R5 = R6 = R7 = R8 = 7 Tnh in tr tng tng ca mch Bi 236 Gii li bi ton trn vi R2 = 7 . Cc in tr khc c gi tr nh c. Bi 237 Cho mch in nh hnh v R1= R5 = R3 = 3 ; R2 = 2 ; R4 = 5 ; U = 3V. Tnh cng dng in qua mi in tr. Bi 238 Cho mch in nh hnh v, mi phn on mch c in tr r (th d nh OA, OC, CD, DB...) Tnh in tr tng ng ca mch khi cho dng in qua mch vo nt A v ra nt B. Bi 239 Gii li bi 238 nhng cho dng in qua mch vo nt C v ra nt D. Bi 240 Gii li bi 238 nhng cho dng in qua mch vo nt C v ra nt B. Bi 241 Gii li bi 238 nhng cho dng in qua mch vo nt A v ra nt O. Bi 242 Cho mch in nh hnh v, mi phn on mch c in tr r (th d nh AE, OH, CH...). Tnh in tr tng ng ca mch khi cho dng in qua mch vo nt A v ra nt B. Bi 243 Gii li bi 242 khi cho dng in qua mch vo nt A v ra nt C. Bi 244 Gii li bi 242 khi cho dng in qua mch vo nt G v ra nt I. Bi 245 Gii li bi 242 khi cho dng in qua mch vo nt A v ra nt O. Bi 246 Cho mch in nh hnh v, mi phn on mch (ca hnh lp phng) c in tr l r (th d nh AB, IH, DC...). Tnh in tr tng ng ca mch khi cho dng in qua mch vo nt A v ra nt C. Bi 247 Gii li bi 246 khi cho dng in qua mch vo nt A v ra nt D.

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Bi 248 Gii li bi 246 khi cho dng in qua mch vo nt A v ra nt H. Bi 249 Cho mch in nh hnh v, mi phn ca on mch (ca hnh ngi sao) u c in tr l r (th d nh AG, GH, KI, HC ...). Tnh in tr tng ng ca mch khi cho dng in qua mch vo nt A v ra nt I. Bi 250 Gii li bi 249 khi cho dng in qua mch vo nt G v ra nt H. Bi 251 Gii li bi 249 khi cho dng in qua mch vo nt L v ra nt I. Bi 252 Gii li bi 249 khi cho dng in qua mch vo nt A v ra nt E. Bi 253 Cho mch in nh hnh v, mi cnh ca mt hnh vung nh u c in tr l r. Tnh in tr tng ng ca mch khi cho dng in qua mch vo A v ra C. Bi 254 C mch in sau: Tnh t A n B th cm th i s c i in tr mc song song v mi in tr c gi tr l ir. Tnh in tr tng ng ca mch. Bi 255 Cho mch in nh hnh v, mi cnh ca hnh tam gic nh u c in tr l r. Tnh in tr tng ng ca mch khi cho dng in qua mch vo nt A v ra nt B. Bi 256 Gii li bi 255 khi cho dng in qua mch vo nt C v ra nt D. Bi 257 C mch in di v hn, mi in tr trong mt cnh ca mt l r. Tnh in tr tng ng ca on mch AB. Bi 258 C mch in nh hnh v. in tr gia M v N l x, cn cc in tr khc l r bit. Hi x bng bao nhiu in tr tng ng ca on mch AB cng l x. Bi 259 C mch in nh hnh v bi 258. Hi x bng bao nhiu in tr tng ng ca on mch AB khng ph thuc vo s in tr. Bi 260

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Cho mch in di v hn nh sau. Tnh in tr tng ng ca mch. Bit R1 = 4 ; R2 = 3 ; Bi 261 Cho mch in di v hn nh sau. Tnh in tr tng ng ca mch. Bit mi in tr trong mch c gi tr r. Bi 262 Cho mch in di v hn khi ko ra v cng v hai pha ca AB. Tnh in tr tng ng ca on mch AB. Bit mi in tr trong mch c gi tr l r. Bi 263 Cho mch in c 5 nt, gia 2 nt c 1 in tr l r. Cho dng in vo 1 nt v ra 1 nt khc bt k. Tnh in tr tng ng ca mch. p dng cho mch c n nt. Bi 264 C hai loi in tr 2 v 5 . Hi phi dng mi loi bao nhiu khi ghp chng ni tip nhau ta c in tr tng ng ca mch l 30 . Bi 265 1 C ba loi in tr 5 , 3 , , tng ba loi in tr ny l 100 chic. Hi phi dng mi 3 loi bao nhiu chic khi ghp chng ni tip nhau ta c in tr tng ng ca mch l 100 . Bi 266 Mt in k c in tr 20 o c dng in ln nht l 1 mA. Mun bin in k ny thnh ampe k o c dng in ln nht l 1A th phi mc thm mt sn c in tr l bao nhiu ? Bi 267 Mt in k c in tr 12 o c dng in ln nht l 1 mA. Mun bin in k ny thnh vn k o c hiu in th ln nht l 12V th phi mc thm mt in tr ph c in tr l bao nhiu ? Bi 268 Mt in k c in tr 20 , c 100 chia. 1. in k ny chu c dng in ln nht l 6 mA. Hi mi chia c gi tr l bao nhiu ? 2. Mc mt sn 1 bin in ny thnh ampe k. Hi ampe k ny o c dng ln nht l bao nhiu ? nhy ca in k thay i ra sao ? Gi tr mi chia tng ng c gi tr l bao nhiu? 3. Mun o dng in ln nht l 1A th phi lm th no ? (gii bi ton khi cha c sn 1 v khi c sn 1 cu 2) Bi 269

24

C mt in k G m khi mc in tr sn thm N1 ln, cn mc 1.

Rs1 (dng lm ampe k) th gii hn o tng

Rs2

th tng thm N2 ln. Hi gii hn do s tng ln bao nhiu ln khi mc: 2.

Rs1

ni tip

Rs2

Rs1 song song Rs2

Bi 270 Mt ampe k c s cu to nh hnh v. Nu dng hai cht 1 v 2 th o c cng dng in ln nht l 2A. Nu dng hai cht 2 v 3 th o c cng dng in ln nht l 3A. Hi nu dng hai cht 1 v 3 th o c cng ln nht l bao nhiu ? Bi 271 Mt vn k c s cu to nh hnh v. in k G c in tr 10 v chu c hiu in th ln nht l 0,2V. Khi dng hai cht 1 v 2 th hiu in th o c ln nht l 5V, dng hai cht 1 v 3 l 25V; dng hai cht 1 v 4 l 250V. Tnh cc in tr ph R1, R2, R3. Bi 272 C mt in k G m khi mc in tr ph R 1 (dng lm vn k) th gii hn o tng N 1 ln, cn mc R2 th tng thm N2 ln. Hi gii hn o s tng ln bao nhiu ln khi mc: 1. R1 ni tip R2. 2. R1 song song R2. Bi 273 Mt vn k c ghi chia ti 120V, in tr Rv = 12k . 1. Nu mc thm in tr ph Rp = 24 k th vn k o c hiu in th ln nht l bao nhiu ? 2. Mun o hiu in th ln nht l 720V th phi lm th no ? (Gii bi ton khi cha c in tr ph Rp = 24k v khi c in tr ph Rp.) Bi 274 Mt ampe k c cu to nh hnh v. Hai kha k1, k2 c in tr khng ng k. in k G c in tr Rg = 20 v chu c dng in ln nht l 2mA. Tnh cc in tr Rs1 , Rs2 , Rs3 . Bit khi k1, k2 u m th gii hn o l 42mA; khi k1, k2 u ng th gii hn o l 82 mA. Bi 275 Mt ampe k c cu to nh hnh v. in k G c in tr 40 v chu c dng in ln nht l 2mA. Khi dng cht 1 v 2 th gii hn o l 100mA, dng hai cht 1 v 3 gii hn o l 30mA, ding hai cht 1 v 4 gii hn o l 10mA. Hi gii hn o l bao nhiu khi dng hai cht: 1. 2 v 3 2. 2 v 4 3. 3 v 4 Bi 276

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o in tr x bng vn k (c in tr Rv) v ampe k (c in tr l Ra). Ngi ta dng mt trong hai s sau: Gi tr ca x c tnh gn ng lU vi U l s ch ca vn k v I l s ch ca ampe I

k. Hi nn dng s no? Bi 277 C hai in tr R1, R2 mc ni tip nhau gia hai im c hiu in th khng i U. Khi ln lt mc vn k gia A v B, A v C, C v B th vn k ln lt ch 180V, 60V, 100V. Tnh sai s tng i ca php o hiu in th trn R1 v R2. Bi 278 C hai in tr R1, R2 mc song song gia hai im c hiu in th khng i U = 10V. Khi mc mt ampe k (c in tr Ra = 1 ) o dng qua R1 th ampe k ch 1A, o dng qua R2 th ampe k ch 2A. Tnh sai s tng i ca php o cng dng in qua R1 v qua R2. Bi 279 Mt ampe c 100 chia, mi chia tng ng vi 2mA. 1. Tnh gii hn o ca ampe k. 2. Nu dng mt in tr sn l Rs = 0,1 th kh nng o tng ln 10 ln. Tnh gi tr mi chia tng ng. 3. Mun bin ampe k trn thnh mt vn k o c hiu in th ln nht l 36V th phi mc mt in tr ph Rp bng bao nhiu? Bi 280 Mt in k c in tr 5 v c 100 chia. Khi dng in qua in k c cng 20mA th kim in k ch chia 50. 1. Hi phi mc thm mt in tr ph ( thnh vn k) bng bao nhiu khi o hiu in th 16V th kim in k ch chia 10. 2. Hi phi mc thm mt in tr ph ( thnh vn k) bng bao nhiu khi o hiu in th 16V th kim in k ch chia 10. Bi 281 Cho mch in nh hnh v. o cng dng in qua R = 20 vi sai s tng i khng qu 4% th phi dng ampe k c in tr l bao nhiu? Bi 282 Cho mch in nh hnh v o hiu in th hai u R1 vi sai s tng i khng qua 5% th phi dng ampe k c in tr l bao nhiu? p dng s cho R1 = 200 v R2 = 1000 . Bi 283

26

C mt mch phn th nh hnh v, ta c: RAB = R 0, RAC = x, vn k c in tr Rv. Hiu in th hai u mch l U. Tnh s ch ca vn k. Bi 284 Cho mch in nh hnh v. R1 = 40 , R2 = 20 , C1 = 10 F, C2 = 15 F, U = 30V, in tr kha K khng ng k. Tnh hiu in th v in tch trn cc t khi: 1. K m. 2. K ng. Bit lc u K m v cc t cha tch in. Bi 285 C mch in nh hnh v: U = 60V, C1 = 10 F, C2 = 20 F, C3 = 30 F. Tnh in tch trn mi t. Bit trc khi ni vo mch cc t cha tch in. Bi 286 C mch in nh hnh v: R1 = R2 = R3 = 6 ; R4 = 2 , U = 18V F, C 1 = C2 = 6 C3 = 12 F, RK Tnh hiu in th v in tch trn mi t khi: 1. K m 2. K ng. Bit lc u cc t cha tch in. Bi 287 C mch in nh hnh v: R1 = 4 ; R2 = 8 C1 = 10 F, C2 = 5 F, Tnh in tch trn cc t khi: 1. K m. 2. K ng.

0.

R3 = 6 ; U = 9V RK 0

Bi 288 C mch in nh hnh v. R1 = 6 ; R2 = 12 U = 18V; C1 = 4 F; C2 = 5 F; C3 = 20 F; RK 0 Tnh in tch v hiu in th trn cc t khi: 1. K m. 2. K ng. Bit lc u cc t cha tch in. Bi 289 Cho mch in nh hnh v: U = 6V, R1 = 2 ; R2 = 6 R3 = 4 , R4 = 3 , C = 10 F Cc ampe k v kha K c in tr khng ng k. Bit lc u t cha tch in. Tm in tch trn t v s ch cc ampe k khi: 1. K m. 2. K ng.

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Bi 290 C mch in nh hnh v: U = 12V, R1 = 2 ; R2 = 4 R3 = 6 , RK 0 C1 = 15 F Bit lc u cc t cha tch in v K m. Tnh in tch trn cc t khi: 1. K m. 2. K ng. Bi 291 Cho mch in nh hnh v: R1 = 6 ; R2 = 12 U = 9V; C1 = 12 F; C2 = 24 F Cc kha K c in tr khng ng k. Tnh in tch v hiu in th trn cc t trong cc trng hp: 1. K1 v K2 u ng. 2. K1 ng, K2 m. 3. K1 m, K2 ng. Bit trc khi c cc trng hp xy ra th cc t cha tch in. Bi 292 Cho mch in nh hnh v: e = 1,5V; r =1 ; 3

R1 = 4 ; R2 = 8 . Tnh:

1. Cng dng in qua mi in tr. 2. Hiu in th gia hai cc ngun in. Bi 293 Cho mch in nh hnh v: e = 3V; R1 = 5 . Ampe k c Ra ngun.

0, V ch 1,2V, A ch 0,3 V. Tnh in tr trong r ca

Bi 294 Cho mch in nh hnh v R1 = 6 , R2 = 5,5 V c in tr RV rt ln, A v K c in tr rt nh. * Khi K m, V ch 6V. * Khi K ng, V ch 5,75V v A ch 0,5A. Tnh sut in ng e v in tr trong r ca ngun. Bi 295 Mt ngun in c sut in ng e = 1,5V; in tr r = 0,1 . Mc gia hai cc ngun hai in tr R1 v R2. Khi R1 ni tip R2 th cng dng in qua mi in tr l 1,5A. Khi R1 song song R2 th cng dng in tng cng qua R1 v R2 l 5A. Tnh R1 v = R2. Bi 296 C mch in nh hnh v

28

e = 6V; r = 1 ; R1 = 20 ; R2 = 30 ; R3 = 5 . Tnh cng dng in qua mi in tr v hiu in th hai u mch ngoi. Bi 297 Cho mch in nh hnh v. Cc vn k c in tr rt ln, ampe k v kho K c in tr rt nh. K m, V ch 16V. K ng, V1 ch 10V, V2 ch 12V, A ch 1A. Tnh in tr trong ca ngun. Bit R3 = 2R1. Bi 298 C mch in nh hnh v. e = 12,5V; r = 1 ; R1 = 10 ; R2 = 30 ; R3 = 20 ; R4 = 40 . Tnh: 1. Cng dng in qua mi in tr. 2. Cng sut trn in tr R2. 3. Hiu in th gia M v N. Mun o hiu in th ny th cc dng ca vn k mc vo im no ? Bi 299 C mch in nh hnh v. R1 = 12 ; R2 = 16 ; R3 = 8 ; R4 = 11 ; RK Tnh hiu in th gia A v N khi: 1. K m. 2. K ng.

0; e

12V; r = 1 .

Bi 300 Cho mch in nh hnh v. e = 6V; r = 1 Cc ampe k v kha K c in tr khng ng k. R1 = 6 ; R2 = 4 R4 = 3 ; R5 = 5 1. Khi K m, A1 ch 0,5A. Tnh R3 v nhit lng ta ra trn R3 trong 5 pht. 2. Tnh s ch cc ampe k khi K ng. Bi 301 C mch in nh hnh v. Ngun c sut in ng e, in tr trong r = kha K c in tr khng ng k. R1 = R2 = R3 = 6 ; R4 = 2 . 1. Khi moK m, V ch 12V. Tnh e. 2. Tnh s ch V v A khi K ng. Bi 302 C mch in nh hnh v. e = 6V; r = 1 ; R1 = R4 = R5 = 4 ;2 ; vn k c in tr rt ln. Ampe k v 3

R2 = 8 ; R3 = 2 ;

29

RK 0. Tnh hiu in th gia N v B khi: 1. K m; 2. K ng. Bi 303 Cho mch in nh hnh v. e = 9V; r = 1 ; R1 = 5,6 ; R3 = 8 ; R4 = 2 R2 = R5 = R6 = 4 Cc ampe k v kha k c in tr khng ng k. Tm s ch cc ampe k khi: 1. K m. 2. K ng. Bi 304 Cho mch in nh hnh v: e = 9V; r = 1 ; : 6V - 3W Tnh gi tr ca bin tr Rb tham gia vo mch n sng bnh thng. Bi 305 Cho mch in nh hnh v. e = 9V; r = 1 ; 1 : 6V - 3W; 2 3V - 1,5W. Cc n sng bnh thng. Tnh: 1. in tr R1 v R2. 2. Cng sut v hiu sut ca ngun.

Bi 306 Mt ngun in c sut in ng e = 24V; in tr trong r = 3 . C mt s bang n loi 2,4V - 1,44W. Ngi ta mc cc bng trn thnh m dy, mi dy c n bng. Hi phi dng bao nhiu bng v mc nh th no cc bng u sng bnh thng. Bi 307 Mt ngun in c sut in ng e = 24V; in tr trong r = 3 . C mt s bng n loi 2,4V - 1,44W. Ngi ta mc cc bng trn thnh m dy, mi dy c n bang. Hi phi dng bao nhiu bng v mc nh th no cc bng u sng bnh thng. Bi 308 Cho mch in nh hnh v E = 12V; r = 1 . R l bin tr. 1. iu chnh R cng sut mch ngoi l 11W. Tnh gi tr R tng ng. Tnh cng sut ca ngun trong trng hp ny. 2. Phi iu chnh R c gi tr l bao nhiu cng sut trn R l ln nht Bi 309 Cho mch in nh hnh v: e = 12V; r = 3 ; R1 = 12 . Hi R2 bng bao nhiu cng sut mch ngoi l ln nht ? Tnh cng sut ny. Bi 310

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e = 24V; r = 6 ; R1 = 4 . R2 l bin tr. Hi R2 bng bao nhiu cng sut: 1. Mch ngoi ln nht. Tnh cng sut ngun trong trng hp ny. 2. Trn R2 ln nht. Tnh cng sut ny. Bi 311 e = 12V; r = 1 R1 = 6 ; R3 = 4 R2 l bin tr. Hi R2 bng bao nhiu cng sut trn R2 l ln nht. Bi 312 Cho mch in nh hnh v. 4 pin ging nhau mc ni tip, mi pin c sut in ng e = 1,5V; in tr trong r = 0,25 ; R1 = 24 ; R2 = 12 ; R3 = 3 . Tnh: 1. Sut in ng v in tr trong ca b ngun. 2. Cng dng in mch chnh. 3. Cng sut tiu th trn R2. Bi 313 Cho mch in nh hnh v. 4 pin ging nhau mc ni tip, mi pin c sut in ng l e 0 v in tr trong l r0 = 0,25 . R2 = 3 ; R3 = 15 ; R4 = 10 . in tr ca ampe k A rt nh, ca vn k V rt ln. A ch1. A v V ch 2V. Tnh: 3

1. in tr R1. 2. Cng dng in mch chnh. 3. Hiu in th hai u mch ngoi. 4. Sut in ng ca 1 pin. Bi 314 Cho mch in nh hnh v. e1 = 2V; e2 = 4V; e3 = 3V; r1 = r2 = r3 = 0,1 ; R = 8,7 . Tnh cng dng in qua mch v cng sut mch ngoi, cng sut ca b ngun. Bi 315 e1 = e3 = 6V; e2 = 3V r1 = r2 = r3 = 1 R1 = R2 = R3 = 5 Tnh: 1. Sut in ng v in tr trong ca b ngun. 2. Hiu in th gia M v N.

R4 = 10

Bi 316 e3 = 16V; e2 = e1 = 2V; r1 = r2 = r3 = 0,5 R1 = R2 = R3 = 6 R4 = 6,5 Tnh: 1. Sut in ng v in tr trong b ngun. 2. Hiu in th gia A v M. Bi 317 C mch in nh hnh v.

31

3 pin ging nhau, mi pin c e = 6V; r = 0,3 . in tr R = 5,9 Tnh: 1. Hiu in th hai u b ngun. 2. Cng dng in qua 1 pin. 3. Cng sut ca b ngun v cng sut 1 pin.

Bi 318 Hai ngun ging nhau; mi ngun c sut in ng e v in tr trong r. Vn k V v ampe k A l tng. Kha K c in tr khng ng k.

Khi k m, V ch 6V. Khi K ng, V ch 5,5V v ampe k ch 1A.Tnh: 1. e, r. 2. Cng sut mch ngoi khi K ng.

Bi 318 Hai ngun ging nhau; mi ngun c sut in ng e v in tr trong r. Vn k V v ampe k A l tng. Kha K c in tr khng ng k.

Khi k m, V ch 6V. Khi K ng, V ch 5,5V v ampe k ch 1A.Tnh: 1. e, r. 2. Cng sut mch ngoi khi K ng.

Bi 319 e1 = 8V; e2 = 10V r1 = r2 = 2 ; R = 9 Vn k V v ampe k A l cc dng c o in l tng. Tm s ch ca V v A. Bi 320 e1 = 6V; e2 = 4V Tnh:

r1 = r2 = 2 ; R = 9

1. Sut in ng v in tr trong ca b ngun. 2. Cng sut mch ngoi v cng dng in qua mi ngun.Bi 321 Hai ngun c sut in l e1, e2; in tr trong r1 v r2 (gi s e1 > e2). Mch ngoi c in tr R thay i c. Tnh R ngun th hai: 1. Pht dng. 2.Thu dng. 3. Khng pht, khng thu. Bi 322

32

C 6 ngun ging nhau, 1 ngun c sut in ng e = 2V; in tr trong r = 0,5 . in tr ca ampe k A v kha K khng ng k. R1 = 12 ; khi K m ampe k ch24 27

A. Tnh s ch A khi K ng. Bi 323 C 12 ngun ging nhau, 1 ngun c sut in ng e, in tr trong r = 1,5 . Vn k c in tr rt ln v ch 7V. Cng sut mch ngoi l 3,5W. Tnh 1. Sut in ng e. 2. Cng sut mt ngun v cng sut b ngun. Bi 324 Cho mch in nh hnh v: C 10 ngun ging nhau, mi ngun c sut in ng e = 1,5V, in tr trong r = 0,5 mc thnh hai dy song song, dy 1 c 6 ngun ni tip, dy 2 c 4 ngun ni tip. Ampe k c in tr khng ng k. R l bin tr. Hi phi chnh R bng bao nhiu ampe k ch 0. Bi 325 C 12 ngun ging nhau, 1 ngun c sut in ng e = 2V, in tr trong r = 0,5 . in tr R = 13 . Tnh hiu in th gia M v B. Bi 326 C 4 ngun ging nhau, sut in ng v in tr trong ca 1 ngun l e = 9V; r = 1 . Cc in tr R1 = 2 ; R2 = 2 ; R3 = 6 ; R4 = 12 . in tr ca ampe k khng ng k. Cng dng in qua R1 l 3A. Tnh: 1. in tr R5. 2. S ch ampe k A. Bi 327 Hai ngun ging nhau, mi ngun c e = 4,5V, r = 1 . Cc in tr R1 = 1,4 ; R2 = 6 ; R3 = 2 ; R4 = 8 ; R5 = 6 . V c in tr rt ln, A c in tr rt nh. Tm: 1. S ch ca vn k v ampe k. 2. Hiu in th gia hai im M v N. Bi 328 C N = 40 ngun ging nhau, mi ngun c sut in ng e = 2V; in tr trong r = 1 . 1. Cc ngun in c mc hn tp thnh n nhnh, mi nhnh c m ngun ni tip. Hi c bao nhiu cch mc khc nhau? 2. Dng in tr ngoi R = 2,5 th phi chn cch mc no cng sut mch ngoi ln nht? Tnh cng sut ny. Bi 329

33

1. Hai du in tr ghp vi nhau v mc vo hai im c hiu in th 26V. Khi chng ghp ni tip th dng in qua chng l 2A. Khi chng ghp song song th dng in tng cng qua chng l 18 A. Tnh in tr ca hai dy dn trn. 2. Ngi ta mc ln lt dy th nht ri dy th hai vo hai cc b ngun cng sut ta nhit trn hai dy in tr nh nhau. Tnh in tr nh nhau. Tnh in tr trong b ngun. Bi 330 Mt in tr R = 3 c mc gia hai u ca b ngun mc hn tp gm m nhnh, mi nhnh c n pin ging nhau, mc ni tip. Sut in ng v in tr trong ca mi ngun l e = 2V v r = 0,5 . Tnh s ngun t nht cn ding dng in qua R c cng l 8A. Tnh hiu sut ca b ngun. Bi 331 Hy v dng th s ph thuc ca cng sut ngun in v cng sut tiu th mch ngoi vo in tr mch ngoi. Bit ngun c sut in ng e, in tr trong r. Bi 332 Mt b ngun gm 36 ngun ging nhau ghp hn hp thnh m dy song song, mi dy c n ngun ging nhau mc ni tip. Mi ngun c sut in ng e = 12V; in tr trong r = 2 . Mch ngoi c hiu in th U = 120V v cng sut P = 360W. Tnh m v n. Bi 333 C 8 bng n ging nhau loi 3V - 3W v mc thnh p dy song song, mi dy c q bng ni tip. Mi ngun c sut in ng e = 4V; in tr trong r = 1 . Hi phi dng ti thiu bao nhiu ngun v xc nh cc cch mc b n v b ngun. Bi 334 Cho mch in nh hnh v. e1 = 4V; r1 = 2 ; e2 = 3V; r2= 3 . R l bin tr, ampe k c Ra 0. 1. Chnh R gi tr tham gia vo mch l R1 bng bao nhiu ampe k ch O. 2. Khi con chy C c v tr cu 1, nu dch chuyn C th chiu dng in qua ampe k nh th no? Bi 335 Cho mch in nh hnh v: e1 = 55V; e2 = 10 ; e 3 = 15V; r1 = 0,3 ; r2 = 0,4 ; r3 = 0,1 ; r4 = 0,2 ; R1 = 9,5 ; R2 = 19,6 ; R3 = 4,9 . Tnh cng dng in qua cc nhnh. Bi 336169

34

Cho mch in nh hnh v. Ngun c e = 18V; r = 1,4 . Bng n c ghi 5V - 2,5W. Chnh bin tr Rb = 7 th n sng bnh thng. B l bnh in phn c in tr R1 = 10 . 1. Tnh in tr x. 2. Cho bit bnh in phn cha dung dch CuSO 4, dng cc bng ng. Tnh lng ng bm vo catt ca bnh in phn sau 24h. Bi 337 Cho mch in nh hnh v. B ngun e 1, r1 gm 20 pin c e = 1,2V; r = 0,3 . MN l dy in tr ng cht, tit din u, di 1m c in tr RMN = 6 , ampe k c in tr khng ng k. Khi con chy C cch M mt on MC = 12,5 cm th ampe k ch O. 1. Tnh sut in ng e2. 2. Dng b ngun e1 thp sng 6 n loi 6V - 3W. Hi phi mc nh th no cc n sng bnh thng v c li v mt nng lng. Bi 338 Cho ba ngun e1 = e2; r1 = r2 = r v e3 = 2V; r3 = 0 c mc ln lt theo hai s (1) v (2). Bit R1 = 9 ; R2 = 2; Ra = RK 0 1. Khi K m, dng in trong hai s c chiu nh hnh v v I = 0,56A; I = 0,16A. Tm e, r. 2. Tm s ch ampe k trong hai s khi K ng. Bi 339 Cho mch in nh hnh v. B ngun gc 8 pin ging nhau, 1 pin c e = 2,25V; r = 1 . n ghi 3V; 4,5W; Ra = RK 0; bnh in phn ng nc pha xt, c cc in cc bng bch kim v in tr l R3 = 3 . 1. Khi K m, n sng bnh thng. Tnh R1 v s ch ca ampe k. 2. Khi K ng, ngi ta thy cng sut mch ngoi cc, hy tnh th tch oxy c gii phng in cc trong iu kin chun trong thi gian 16 pht 5 giy. Bi 340 Cho mch in nh hnh v, in tr R = 4,5 . C l t in phng m khong cch gia hai bn l d = 0,2cm. Trong mch trn, cng in trng gia hai bn t l E = 2250V . Tnh sut m

in ng e v ngun, bit in tr trong ca n l r = 0,5 . Bi 341 Cho mch in nh hnh v. Ngun in c sut in ng e = 9V, in tr trong r = 1 . Cc in tr R1 = R2 = R3 = 6 , R4 = 18 . T in c in dung C = 8 F. Tnh in tch ca t. Bi 342 Cho mch in nh hnh v. Cc in tr R1 = R2 = 6 ; R3 = R4 = 5 , ngun c sut in ng e = 18V, in tr trong r = 1 . T c in dung C = 10 F. Tnh in tch trn t.

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Bi 343 Cho mch in nh hnh v, cc ngun c e1 = 12V; r1 = 1 ; e2 = 6V; r2 = 1 . Cc in tr R1 = 4 ; R2 = 6 ; R3 = 3 . T c in dung C = 5 F. Tnh in tch trn t v cho bit bn t no tch in dng. Bi 344 Cho mch in nh hnh v. Cc ngun c e1 = 9V; r1 = 2 ; e2 = 5V; r2 = 2 . Trn bng n c ghi 3V - 3W. T c in dung C = 10 F. Bit n sng bnh thng. Tnh: 1. in tr R1. 2. in tch trn t v cho bit bn t no tch in m. Bi 345 Cho mch in nh hnh v. Ngun c sut in ng e, in tr trong r = 1 . Cc in tr R1 = 15 ; R2 = 10 ; R3 = 5 . T c in dung C = 10 F v in tch trn t l l q = 10 C. Tnh: 1. Sut in ng e 2. Cng sut tiu th trn R2.

Bi 346 Cho mch in nh hnh v. Cc ngun c e1 = 12V; r1 = 1 ; e2 = 9V; r2 = 1 ; in tr ca dy in tr AB l RAB = R = 5 . Tnh phn in tr AC l RAC = x in k G ch 0. Bi 347 Cho mch in nh hnh v. B ngun gm 4 oin ging nhau mc ni tip, mi pin c e = 2V, r = 0,5 . Cc in tr R1 = R2 = 20 , R3 = 10 . Kho K c RK 0. Cc t c in dung C1 = 2 F; C2 = 3 F. Tnh in tch trn cc t trong trng hp K m ri K ng, t suy ra lng in tch chuyn qua R1 khi ng kho K. Bi 348 Cho mch in nh hnh v eb = 70V; rb = 10 . Cc in tr R1 = R2 = R3 = R4 = 20 . in tr kho K l RK 0. T c in dung C = 10 F. Tnh lng in tch chuyn qua R4 trong thi gian K ng ri m. Bi 349 Cho mch in nh hnh v. Ngun c e = 12V; r = 1 ; R2 = 2 ; R3 = 4 . Phn bin tr tham gia vo mch l x. T c in dung C = 10 F. Hi x phi bng bao nhiu : 1. in tch trn t l 3.10-5 C v bn t ni vi M tch in m. 2. Cng sut trn x cc i. Bi 350

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Cho mch in nh hnh v. Cc ngun e1 = 4V; r1 = 0,5 ; e2 = 2V; r2 = 1 . Cc in tr R1 v R2 . Cc t C1 = C2 = 2 F ; C3 = 4 F. C in k c in tr khng ng k. in k G1 ch 0,4A, in k G2 ch 0. 1. Tnh R1 v R2. 2. Tnh in tch v in th trn cc t. Bi 351 Cho mch in nh hnh v. Ngun c e = 4V; r = 1 . Cc in tr R1 = R2 = 2 ; R3 = R4 = R5 = 5 . T c in dung C = 2 F; in tr ampe k v kho K khng ng k. Tnh s ch ampe k, in tch trn t v du in tch trn cc bn t khi: 1. K m. 2. K ng. Bi 352 B ngun c 6 ngun ging nhau mc nh hnh v, mt ngun e = 12V, r = 0,75 . Cc in tr R1 = 2 ; R2 = 3 ; R3 = 10,5 . Cc t c C1 = C2 = 2 F, C3 = 6 F. Tnh lng in tch qua kha K khi K m ri ng. Bi 353 Cho mch in nh hnh v. Hai ngun ging nhau, mt ngun c sut in ng e, in tr trong r. Bng n loi 6V - 6W. Cc t c in dung C1 = C2 = 2 F. in tr R1 = 4 , vn k V c in tr rt ln, kha K c in tr khng ng k.

Khi K m, V ch 12V. Khi K ng th n sng bnh thng.1. Tnh e, r. 2. S ch V khi K ng. 3. in lng ti qua R2 khi K m ri ng v cho bit cc t phng hay np in. Bi 354 Cho mch in nh hnh v; e2 = 10V; r1 = 1 ; r2 = 3 ; R1 = 2 ; R2 = 4 . R3 = R4 = 3 . Vn k c in tr rt ln v ch22 V. Tnh e1. 3

Bi 355 Cho mch in nh hnh v, cc ngun e1 = 24V; r1 = 1 ; e2 = 6V; r2 = 4 ; R3 = 5 . Cc t c in dung C1 = 2 F; C2 = 3 F; C3 = 4 F. Tnh in tch trn cc t. Bi 356 Cho mch in nh hnh v. e1 = 6V; e2 = 12V; r1 = r2 = 2 ; R1 = 10 ; R2 = 5 ; C1 = C2 = 6 F. Tnh in tch trn cc t v in lng qua R1 khi K chuyn t ng sang m.

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Bi 357 C mch in nh hnh v. Cc ngun ging nhau v mi ngun c e = 3V; r = 1 . Cc in tr rt ln. Tm s ch ca cc vn k. Nu thay 2 vn k bng 2 t c in dung bng nhau l C 1 = C2 = 6 F th mi t tch mt lng in tch l bao nhiu? Bi 358 C mch in nh hnh v. Bn ngun ging nhau mc ni tip, 1 ngun c e = 0,75V; r = 0,1 . Cc in tr R1 = 1 ; R3 = 2 ; R4 = 4 ; Ra = RK 0. Bit khi K m, A ch 0,2A v khi K ng K ch 0. Tnh R2 v R5. Bi 359 C mch in nh hnh v. Cc ngun ging nhau, mi ngun c e = 3V; r = 1 . Bin tr c in tr ton phn l RMN = 10 ; in tr R1 = 1 ; Ra 0; RV rt ln. T c in dung C0 = 5. Tm s ch vn k, ampe k, in tch trn t v cng suet b ngun, cng sut 1 ngun khi con chy C ca bin tr v tr: 1. L trung im ca MN 2. Trng vi N. Bi 360 Cho mch in nh hnh v, cc ngun c e1 = 6V; r1 = 0,5 ; e2 = 9V; r2 = 0,5 ; r3 = 10 ; R4 = 0,5 ; R1 = 8 . n c ghi 12V - 18W. Cc t c in dung C1 = 6; C2 = 4. n sng bnh thng. Tnh R2, cng sut mi ngun, cng sut mch ngoi, in tch trn cc t. Bi 361 Cho mch in nh hnh v. Mi ngun c sut in ng e, in tr trong r = 4. Cc in tr R1 = R2 = R3 = 40 ; R4 = 30 . Ampe k c in tr Ra 0 v ch 0,5A. 1. Tnh e 2. Nu thay ampe k bng t c in dung C = 10 F th in tch trn t l bao nhiu? Bi 362 Cho mch in nh hnh v. Ngun c e = 18V; r = 2 . Cc in tr R1 = R2 = R3 = R4 = 6 , kho K c RK 0, t c in dung C = 6 F. Tnh in tch ton cc t v cng dng in qua kho K khi: 1. K m 2. K ng Bi 363 Cc ngun c e1 = 12V; r1 = 2 ; e2 = 6V; r2 = 2 . Cc in tr R1 = R3 = 4 , R2 = 6 , cc kho c RK 0, A c in tr khng ng k. T c in dung C = 6 F. Tm s ch ca ampe k v in tch trn t khi: 1. K1, K2 u m.

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2. K1, K2 u ng. 3. K1 ng , K2 m. 4. K1 m, K2 ng Bi 364 C hai ngun ging ht nhau, mi ngun c sut in ng e, in tr trong r. Tnh hiu in th gia hai im A v B khi mc hai ngun theo hai s sau: Bi 365 Cho mch in nh hnh v. Hai ngun ging nhau, mi ngun c e = 3V, r = 0,5 . Cc in tr R1 = 2 ; R2 = 4 ; R3 = 8 ; R4 = 10 . Kho K v ampe k A c in tr khng ng k, x l in tr cha bit. T c in dung C = 10 F. Khi K m A ch 1,2A. 1. Tnh x, in tch trn t khi K m. 2. Khi K ng, in tch trn t s thay i nh th no? Bi 366 C 12 pin ging nhau, mi pin c sut in ng e = 2V, in tr trong r = 0,1 c, mc thnh b ri ni vi mch ngoi c in tr R = 0,3 . 1. Tnh sut in ng, in tr trong ca b ngun v dng in qua R khi: + 12 pin ghp ni tip + 12 pin ghp song song + 12 pin ghp thnh bn dy, mi dy c 3 pin. 2. Nu gho thnh m dy, mi dy c n pin. Tm cch ghp dng in qua R l ln nht. Tnh Imax. 3. Thay R bng R1 = 0,8 . Ghp b ngun thnh 2 dy, 1 dy c x pin, 1 dy c y pin. Tm cch ghp khng c dng in qua dy c y pin. Bi 367 Cho mch in nh hnh. Bit e = 6V, r = 1 ; R1 = R3= R4 = R5 = 1 , R2 = 0,8 . Rx l bin tr ti a l 10 . Ban u Rx = 2 . 1. Tnh s ch ca ampe k; vn k v cng sut ca Rx khi K m v K ng. 2. K ng, cho Rx thay i t 0 n 10 . S ch ca ampe k tng hay gim? Bit V c in tr rt ln, A v kho K c in tr rt nh. Bi 368 Cho mch in nh hnh v. Bit e1 = e2 = 6V, r1 = 1 ; r2 = 2 ; R1 = 5 ; R2 = 4 ; R = 3 . Vn k c in tr rt ln. 1. Tm cng dng in qua cc in tr v ngun in. 2. S ch ca vn k. Bi 369 Cho mch in nh hnh. Bit e1 = 12V, r1 = 1 ; e2 = 6V; r2 = 1 ; R1 = 2 ; R2 = 3 . 1. nh gi tr ca R e2 l my pht, my thu; khng pht khng thu?

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2. Tnh R dng pht ca e1 gp 2 ln dng thu ca e2. Tnh cng sut ca e1 lc ny. Bi 370 Cho mch in nh hnh. Bit e1 = 12V; r1 = 1 ; e2 = 6V; r2 = 1 ; R1 = 2 ; R2 = 3 . 1. nh gi tr ca R e2 l my pht; my thu; khng pht khng thu ? 2. Tnh R dng pht ca e1 gp 2 ln dng thu ca e2. Tnh cng sut ca e1 lc ny. Bi 371 Cho mch in nh hnh. e = 24V, r = 2 ; R1 = 3 ; R2 = 2 . nh mc Rx : 1. Cng sut mch ngoi ln nht. Tnh gi tr ny. 2. Cng sut trn Rx bng 9W. 3. Cng sut trn Rx cc i. Tnh gi tr ny. Bi 372 Cho mch in nh hnh. Bit e1 = 6V; r1 = 1 ; e2 = 2V; r2 = 0,5 ; R1 = 1 ; R2 = 2 ; R3 = 2,5 ; C = 1 F. 1. Tnh in tch trn t C khi K m, bn no tch in dng. 2. Tm in lng qua R4 khi K ng. Bi 373 Cho mch in nh hnh. Bit R1 = 8 ; R2 = 2 ; R3 = 4 ; R4 = 1 ; e = 12V; r = 0,4 , RA = 0. 1. Chng t rng khiR1 R 3 = th khng c dng in qua ampe k. R2 R4

2. Cho R4 = 4 . Xc nh chiu v cng dng in qua ampe k. 3. Bit dng in qua ampe k c chiu t M n N, cng IA = 0,3A. Tnh R4. Bi 374 Cho mch in nh hnh. B ngun 2 dy, mi dy c 6 pin, mi pin c e = 1,5V; r = 0,2 . in tr cc n ln lt l R1 = 2 ; R2 = R3 = 6 . iu chnh bin tr Rb sao cho vn k ch 5V. Tnh: 1. e1, rb ca b ngun. 2. Cng qua mi n v gi tr ca Rb. 3. Nhit lng to ra bin tr sau 10 pht v cng sut n 1. 4. Nu 2 t, sng cc n cn li ra sao? S ch ca vn k thay i th no? Bit vn k c in tr rt ln. Bi 375 Cho mch in nh hnh v. Mi ngun c e = 1,5V; r = 0,1 . n 1 loi 6V - 3W; n 2 loi 3V - 1,5W. 1. Dch chuyn con chy C n v tr cho cc n sng bnh thng. Tnh: a. Hiu in th hai u ngun.

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b. in tr R1 v gi tr ca bin tr R2 tham gi vo mch. 2. T v tr con chy C cu 1, nu dch chuyn C v pha A th sng n 1 thay i th no? Bi 376 Cho mch in nh hnh v. Bit e = 12V, r = 2 ; R1 = 3 ; R2 = 6 ; R3 = 4 ; R4 = 12 ; RA = 0. Tm s ch ca ampe k khi K m v K ng. Bi 377 Cho mch in nh hinh v. Ngun c e = 4V, r = 1 . Cc in tr R1 = R2 = R3 = R4 = R5 = 1 . Kho K c RK 0. Tnh cng sut ca ngun khi: 1. K m. 2. K ng. Bi 378 Cho hai ngun e1 = 6V; r1 = 1 ; e2 = 12V, r2 = 2 . Cc ampe k c RA = 0. 1. Tm s ch ca ampe k c mc trn hnh. 2. Thay ampe k bng cc vn k c RV rt ln. Tm s ch ca vn k. Bi 379 Gii li bi 378 khi ampe k c mc nh sau: Bi 380 Gii li bi 378 khi ampe k c mc nh sau: Bi 381 Gii li bi 378 khi ampe k c mc nh sau: Bi 382 Cho mch in nh hnh. Bit: e1 = 2V; r1 = 0,1 ; e2 = 6V; r2 = 0,2 ; e3 = 8V; r3 = 0,3 ; R1 = 0,4 ; R2 = 1 ; R3 thay i. 1. Tm dng in qua mch v UMN khi R3 = 2 . 2. C th iu chnh R3 UMN = 0 c khng? Nu c tm gi tr R 3 v dng in qua mch lc ny. Bi 383 Cho mch in nh hnh v. B ngun gm 8 pin ghp thnh 2 dy, mi dy c 4 pin, mi pin c e = 1,5V, r = 0,1 . Bit R1 = 1,8 ; R2 = 4 ; R3 = 3 ; R4 = 6 ; RA = 0; dng in qua R1 l 1A. 1. Tnh sut in ng v in tr trong ca b ngun. 2. Tnh R5. 3. Tm s ch ca ampe k.

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Bi 384 Cho mch in nh hnh. B ngun gm 12 pin ging nhau ghp thnh 2 dy, mi dy c 6 pin, mi pin c e = 1,5V; r = 0,1 ; R1 = 4 ; R2 = 2,4 ; R3 = 3 ; R4= 1,7 ; R A 1 = R A 2 = RK = 0; RV rt ln. Tm s ch cc ampe v vn k khi: 1. K1 ng, K2 m. 2. K1 m, K2 ng. 3. K1, K2 cng ng. Bi 385 Cho mch in nh hnh. Bit e = 12V; r = 1 ; R1= 1 ; R2 = 2 . Rx l bin tr. 1. Khi Rx gi tr 5 . Tm cng sut ca Rx. 2. nh Rx cng sut tiu th trn Rx ln nht. Tnh cng sut ny v cng sut ca ngun. Bi 386 Cho mch in nh hnh. Bit e1 = 10V, r1 = 2 ; e2 = 20V; r2 = 3 ; e3 = 30V; r3 = 3 ; R1 = R2 = 1 ; R3 = 3 ; R4 = 4 ; R5 = 5 ; R6 = 6 ; R7 = 7 . Tm dng in qua cc ngun v UMN. Bi 387 Cho mch in nh hnh. Bit e1 = 6V, r1 = 1 ; e2 = 2V; r2 = 0,5 ; RAB = 8 ; RA = 0. 1. Tm s ch ca ampe k khi con chy C chnh gia AB. 2. Tm v tr ca C ampe k ch 0. Bi 388 Cho mch in nh hnh. Bit e = 12V; r = 1 ; R2 = 3 ; R3 = 10K ; C1 = 3C2 = 1. 1. Tnh lng in tch qua kho K khi K m ri ng, 2. Gii s in tch qua K trong thi gian t = 0,01s. Hy cho bit ln v chiu ca dng in trung bnh qua R3. Nhit lng to ra trn R3 l bao nhiu? Bi 389 Cho mch in nh hnh. Sut in ng v in tr trong mi pin (e = 1,5V, r = 0,5 ). R1 = 1 , R2 = 4 , R3 = 2 , R4 = 1 , R5 = 2 , C = 10 F. 1. Tm dng in qua cc in tr. 2. Tm in tch trn t C. 3. R5 b t, tm in tch trn t lc ny. Bi 390 Cho mch in nh hnh v: e1 = 12V; r1 = 1 ; e2 = 6V; r2 = 2 ; e3 = 9V; r3 = 2 ; R3 = 3 ; C = 10 F. Tnh in tch trn t. Bi 391

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Mt my pht in cung cp in cho mt ng c. Sut in ng v in tr trong ca my pht l e = 25V; r = 1 . Dng in chy qua ng c l 1A, in ca cun dy trong ng c l 1,5 . Tnh: 1. Cng sut ca ngun v hiu sut ca n. 2. Cng sut in ton phn v cng sut c hc ca ng c in. Hiu sut ca ng c, 3. Gi s ng c b kt khng quay c, dng in qua ng c c cng bao nhiu? Bi 392 Mt my bm a c mt khi lng nc l m = 75kg ln bnh cha cao h = 4,7m qua mt ng c tit din S = 0,1m2 trong thi gian t = 1s. Ly g = 10m/s2. 1. Tnh cng hu ch ca my bm. 2. Nu my bm tiu th cng sut l P = 10kW th hiu sut ca n l bao nhiu? Bi 393 Tnh cng sut ca dng in v nhit lng to ra trong acquy sau thi gian t = 10s khi: 1. Acquy np in vi dng in I1 = 2A v hiu in th hai cc acquy l U1 = 20V, sut in ng ca acquy l e = 12V. 2. Acquy pht in vi dng in I2 = 1A. Bi 394 Mt vt kim loi em m kn c din tch S = 150cm 2. Hy xc nh b dy h ca lp kn m trn vt. Bit dng in qua bnh in phn c cng I = 2A, thi gian m 30 pht; nguyn t lng, ho tr v khi lng ring ca ln ln lt l A = 5; n = 2; D = 8,8.103 kg/m3. Bi 395 Ngi ta in phn dung dch mui n (NaCl) trong bnh c vch ngn vi cc in cc bng bch kim. catt ngi ta thu c 0,4 lt kh hir p sut 1,2atm, nhit 270C. 1. Tnh cng thc hin ca dng in. Bit hiu in th hai cc bnh in in l 20V, kh hir c A = 1, n = 1. 2. Tnh hiu sut ca bnh in phn. Bit in tr ca bnh l r = 2 v thi gian in phn l 31 pht 21 giy. Bi 396 Cho mch in nh hnh v. Ngun c sut in ng e, in tr trong r. Cc ampe k ging nhau v mi ampe k c in tr l Ra. Ampe k A1 ch 1,5A; A2 ch 2A. 1. Tm s ch ca A3, A4 v cng dng in qua R. 2. Cho R = 1,5 . Tnh Ra. Bi 397 Cho mch in nh hnh v. Ngun c sut in ng e, in tr trong r = 1,8 . Hai vn k ging nhau v mi vn k c in tr l Rv. Bit V1 ch 7V, V2 ch 3V; R0 = 300 ; Ra 0. Tnh: 1. Rv.

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2. S ch ca A. 3. e Bi 398 Cho mch in nh hnh v. Ngun c sut in ng e = 20V, in tr trong r =R0 . Cc 4

in tr R1 = R2 = R3 = R4 = R0. Vn k V ch 5V. Tnh hiu in th hai u ngun. Bit vn k c in tr l Rv. Bi 399 Ngun c sut in ng e, in tr trong r = R0. Cc in tr R1 = R2 = R0. Hai vn k ging nhau c in tr l Rv. Vn k V1 ch 10V; V2 ch 4V. Tnh e. Bi 400 Cho mch in nh hnh v. Cc ngun c e1 = 1,9V, r1 = 0,3 ; e2 = 1,7 ; r2 = 0,1 ; e3= 1,6V; r3 = 0,1 . Ampe k A ch 0. Tnh R v cng dng in qua cc nhnh. Phn VI: t trng Bi 401 Mt dng in 20A chy trong mt dy dn thng di t trong khng kh. a. Tnh cm ng t ti nhng im cch dy dn 10cm. b. Tm nhng im ti cm ng t ln gp i, nh bng na gi tr ca B tnh cu a. Bi 402 Hai dy dn di song song nhau nm c nh trong mt phng P v cch nhau mt khong d. Dng in trong hai dy dn c cng cng I. Tnh cm ng t ti nhng im nm trong mt phng P v cch u hai dy dn trong hai trng hp: a. Dng in trong hai dy dn cng chiu. b. Dng in trong hai dy dn ngc chiu. Cho I = 10A, d = 8 cm. Cc dy dn t trong khng kh. Bi 403 Mt khung dy trn, bn knh 30cm gm 10 vng dy. Cm ng t ti tm ca khung dy B = 3,14.10-5T. Xc nh cng dng in qua khung dy. Bi 404 Mt si dy dn rt di cng thng, khong gia c un thnh mt vng trn nh hnh. Bn knh vng trn R = 6cm. Cho cng dng in chy qua dy dn I = 3,75A. Xc nh cm ng t ti tm ca vng trn.

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Bi 405 Hai dy dn thng, di v hn trng vi hai trc to vung gc xOy. Dng in qua dy Ox, Oy ln lt l I1 = 2A; I2 = 5A. Hy xc nh: a. Cm ng t ti im A c to x = 2cm; y = 4cm. b. Tp hp cc im c cm ng t bng 0. Bi 406 Hai dy dn thng di t song song cch nhau 50cm c dng in ln lt l I1 = 3A; I2 = 2A. Xc nh cm ng t ti im M cch dng I1 30 cm, cch dng I2 40 cm. Bi 407 Mt vng dy hnh trn c ni vi hai dy dn thng di v hn vo ngun in nh hnh v. Bit hai ng thng AM v Mn qua tm O ca vng dy. Tnh cm ng t do dng in gy ra ti tm O ca vng dy. Bi 408 Mt dy ng c ng knh d = 0,8 mm c ph sn cch in rt mng. Ngi ta dng dy ny qun ng dy c ng knh D = 2cm di l = 40 cm. Nu mun t trng trong ng dy c cm ng tfw B = 6,28.10-3T th phi t ng dy vo hiu in th bao nhiu? Bi 409 Ba dy dn thng, song song di v hn cng nm trong mt mt phng, hai dy lin tip cch nhau mt on a = 6cm, ng I1 = I2; I3 = 2I. Dy c I3 nm ngoi I1, I2 v dng I3 ngc chiu I1, I3. Tm v tr cc im c cm ng t bng 0.

Bi 410 Cho hai dy dn thng song song di v hn, t cch nhau mt khong 2a = 20 cm trong chn khng. Hai dng in cng chiu v cng cng I = 10A i qua hai dy. Mt mt phng P vung gc vi hai dy v ct chng ti A1, A2. M l mt im trn ng trung trc ox ca A1A2. t OM = x. a. Xc nh cm ng t to b hai dng in trn ti M. Xtes trng hp x = 20cm. b. Tm im M0 trn ox m ti cm ng t l cc i v tnh cc i y. Bi 411 Cho mt on dy dn ng cht c khi lng m = 10g, di l = 30cm. u trn ca on dy c treo vo im O v c th quay t do chung quanh O. u di ca on dy chm vo thu ngn ng trong mt chic chu. Khi cho dng in c cng I = 8A chy qua on dy v t ton b on dy trong t trng u c phng nm ngang th on dy lc ra khi phng thng ng mt gc = 50. Hy xc nh cm ng t B. Ly g = 9,8 m/s2.

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Bi 412 On dy dn MN c chiu di l = 20cm, khi lng m = 10g c treo nm ngang bng hai dy mnh AM, BN. Thanh MN t trong t trng u B thng ng hng ln vi B = 0,5T. Khi cho dng in I chy qua, on dy MN dch chuyn n v tr cn bng mi, lc hai dy treo AM, BN hp vi phng ng mt gc = 300. Xc nh I v lc cng dy treo. Ly g = 10 m/s2. Bi 413 Khung dy ABCD hnh vung cnh a c th quay d dng quanh cnh AB c nh nm ngang. Khing c t trong t trng u B c phng thng ng hng ln. Cho dng in I chy qua khung dy, khi cn bng mt phng khung hp vi phng ng mt gc . Tnh bit tit din dy lm khung l S, c khi lng ring D. Bi 414 Mt khung dy dn c dng tam gic vung cn ADC nh hnh v. Khung dy t vo t trng u c cm ng t B = 0,1T, B vung gc vi mt phng ABC. Cho AD = AC = 20 cm, dng in chy qua khung I = 5A theo chiu CADC. Xc nh lc t tc dng ln cc cnh ca khung dy. H lc ny lm khung chuyn ng ra sao khu khung t do. B qua trng lng ca khung dy. Bi 415 Mt khung dy hnh vung cnh a = 10cm c dng in I = 1A chy qua. Khung t cnh mt dy dn thng di c dng in I1 = 2A cch cnh gn nht ca khung dy mt on a nh hnh v. a. Xc nh lc t tng hp ln khung dy. b. t thm mt dy dn thng di c dng in I1 cng nm trong mt phng khung dy (vung gc vi dy ban u) sao cho ng cho BD ca khung di qua giao im ca hai dy ny. Xc nh t tng hp lc ny. Bi 416 Mt vng dy dn bn knh R = 20cm nm trong mt phng thng ng. tm vng dy c t mt kim nam chm nh c th quay t do quanh trc thng ng trn mt mt chia . Ban u kim nam chm nm theo phng Nam - Bc ca t trng Tri t, mt phng vng dy song song vi trc kim. a. Cho dng in I1 = 4,5A qua dy, kim chm quay mt gc = 300. Tm cm ng t B ca 1 t trng Tri t ti ni lm th nghim. b. kim lch mt gc 2 = 600 th phi cho dng in qua vng dy I2 l bao nhiu? Bi 417 Khung dy hnh ch nht din tch S = 20 cm2 gm 50 vng dy. Khung dy t thng ng trong t trng u c B nm ngang, B = 0,2T. Cho dng in I = 1A qua khung. Tnh momen lc t ln khung khi:

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a. B song song mt phng khung dy. b. B hp vi mt phng khung mt gc 300. Bi 418 Hai thanh ray nm ngang v cch nhau mt khong l = 20cm. Mt thanh kim loi MN, khi lng m = 100g t ln trn, vung gc vi thanh ray. Dng in qua thanh MN l I = 5A. H thng t trong t trng u B thng ng, hng ln, vi B = 0,2T. Thanh ray MN nm yn. Xc nh h s ma st gia thanh MN v hai thanh ray, ly g = 10 m/s2.

Bi 419 Hai thanh kim loi AB, CD t nm ngang, song song, cch nhau l = 20 cm, hai u thanh c ni vi ngun in c = 12V, r = 1 . Thanh MN c in tr R = 2 , khi lng m = 100 g t vung gc vi hai thanh AB, CD v c th trt trn hai thanh ny vi h s ma st k = 0,2. H thng t trong t trng u thng ng, hng ln vi B = 0,4T nh hnh v. B qua in tr cc thanh ray. a. Tnh gia tc chuyn ng ca ray MN, ly g = 10 m/s2. b. Cn phi nng hai u BD ca thanh hp vi phng ngang mt gc bng bao nhiu thanh MN trt xung hai u A, C vi gia tc nh cu a. Bi 420 Mt in tch chuyn ng trong t trng u. Mt phng qu o ca ht vung gc vi ng cm ng t. Nu in tch chuyn ng vi vn tc v1 = 106 Lorentz tc dng ln in tch l f1 = 3.10-6 N. Hi nu in tch chuyn ng vi vn tc v 2 = 2,5.106 m/s th lc f2 tc dng ln in tch l bao nhiu? Bi 421 Mt in tch c khi lng m1 = 1,60.10-27 kg, c in tch q1 = -e chuyn ng vo t trng u B = 0,4T vi vn tc v1 = 106 m/s. Bit

v

B.

a. Tnh bn knh qu o ca in tch b. Mt in tch th hai c khi lng m2 = 9,60.10-27 kg, in tch q2 = 2e khi bay vung gc vo t trng trn s c bn knh qu o gp 2 ln in tch th nht. Tnh vn tc ca in tch th hai. Bi 422 Mt electron trong n hnh ca my thu hnh c nng lng W = 12kev. ng c t sao cho electron chuyn ng nm ngang theo hng Nam - Bc a l. Cho bit thnh phn thng ng ca t trng Tri t c cm ng t B = 5,5.10-5 T v hng xung.

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a. Di tc dng ca t trng Tri t, electron b lch v pha no? Tnh gia tc a ca electron di tc dng ca lc t. b. Sauk hi bay c mt on l = 20cm trong ng, tia electron b lch i mt khong S bng bao nhiu? B qua tc dng ca trng lc.

Bi 423 Mt dng in I chy qua thanh dn bng ng c tit din hnh ch nht (a = 1mm; b = 2mm). Thanh t trong t trng u c B = 0,2T; B b v dng in. Cho vn tc chuyn ng ca electron l .10-4 m/s. Tnh hiu in th xut hin gia cc cnh ca thanh dn, cho thi gian ln. Phn VII: Cm ng in t Bi 424 Tm chiu ca dng in cm ng xut hin trong cc trng hp sau: 1. a thanh nam chm ra xa khung dy. (h.a) 2. Tng dng in qua dy dn. (h.b) 3. Cho khung chuyn ng theo chiu v . (h.c) Bi 425 Mt vng dy ng c ng knh D = 20cm, tit din dy s = 0,5 mm2 t vo trong t trng u c cm ng t B vung gc mt phng vng dy. Tnh tc bin thin ca cm ng t qua vng dy dng in cm ng xut hin trong vng dy l 2A. Cho in tr sut ca ng = 1,75.10-8 m. Bi 426 Mt vng dy trn c bn knh R = 10cm, t trong t trng u B = 10-2T. Mt phng vng dy vung gc vi cc ng cm ng. Sau thi gian t = 10-2 s, t thng gim u n 0. Tnh sut in ng cm ng xut hin trong vng dy. Bi 427 Mt vng dy trn ng knh D = 10cm, in tr R = 0,1 t nghing mt gc 600 vi cm ng t B ca t trng u nh hnh. Xc nh sut in ng cm ng, ln v chiu ca dng in cm ng xut hin trong vng dy nu trong thi gian t = 0,029 s. a. T trng gim u t B = 0,4T xung 0 b. T trng tng u t B1 = 0,1T n B2 = 0,5T.

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c. T trng khng i B = 0,4T nhng quay u vng dy n v tr m cm ng t B trng vi mt phng vng dy. Bi 428 Mt cun dy c 500 vng, din tch mi vng S = 10 cm 2 c trc song song vi B ca t trng u. Tnh bin thin ca cm ng t trong thi gian t = 10-2 s nu sut in ng cm ng c ln 5V. Bi 429 Khung dy ABCD t thng ng, mt phn khung nm trong t trng u B nh hnh. B = 1T trong khong MNPQ, B = 0 ngoi khong . Cho AB = l = 5cm, khung c in tr R = 2 . Khung di chuyn u xung di vi vn tc 2 m/s. Tnh dng in cm ng qua khung v nhit lng to ra trong khung khi n di chuyn mt on x = 10cm (cnh AB cha ra khi t trng). Bi 430 Mt khung dy hnh vung, ABCD, cnh a = 20cm, in tr tng cng R = 0,8 , trn c cc ngun E1 = 12V; r1 = 0,1 ; E2 = 8V; v2 = 0,1 mc nh hnh v. Mch c t trong t trng u B vung gc vi mt phng ca khung. a. Cho B tng theo thi gian bng quy lut B = k.t (k = 40 T/s). Tnh I chy qua khung dy. b. dng in qua khung dy bng 0, t trng phi thay i th no? Bi 431 Mt vng dy c in tch S = 100 cm 2 , hai u ni vi t c in dung C = 5 F. Mt phng vng dy t vung gc vi cc ng cm ng ca t trng B = kt; (k = 0,5 T/s). a. Tnh in tch trn t. b. Nu khng c t th cng sut to nhit trn vng dy l bao nhiu? Cho in tr ca vng dy R = 0,1 . Bi 432 Mt thanh kim loi di l = 1,2 m quay trong t trng u c B vung gc vi thanh (B = 0,2T). Tm hiu in th hai u thanh khi thanh quay quanh trc vi tn s gc n = 120 vng/pht khi: a. Trc quay qua mt u thanh. b. Trc quay qua mt im trn thanh, cch mt u mt qua l = 20cm. Bi 433

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Mt cun dy c 100 vng, bn knh 10 cm. Tr ca cun dy song song vi cm ng t B ca mt t trng u B = 0,2T. Ta quay u cun dy sao cho sau 0,5s trc ca n vung gc vi vect B . Tnh sut in ng cm ng xut hin trong cun dy. Bi 434 Mt on dy MN di l = 10 cm c treo nm ngang bng hai dy dn mnh, nh, thng ng, di L = 0,9m.

H thng c t trong t trng u B thng ng hng xung, B = 0,2T. Ko lch dy MN dy treo hp vi phng ng mt gc 0 = 600 ri bung ra. a. Tm biu thc sut in ng cmar ng xut hin trong dy MN khi dy treo lch mt gc vi phng ng. b. Tm gi tr sut in ng cc i. B qua sc cn ca khng kh, ly g = 10 m/s2.

Bi 435 Cho mch in nh hnh v, E = 1,2V, r = 1 , MN = l = 40cm; RMN = 3 , vung gc vi khung dy, B = 0,4T. B qua in tr cc phn cn li ca khung dy. Thanh MN c th trt khng ma st trn hai thanh ray. a. Thanh MN chuyn ng u sang phi vi vn tc v = 2m/s. Tm dng in qua mch v lc t tc dng vo thanh MN. b. khng c dng in qua mch, MN phi chuyn ng theo hng no? Vi vn tc bao nhiu? Bi 436 Mt dy dn c un thnh mch in thng c dng hai hnh vung cnh a = 10cm, b = 20cm nh hnh v. Mch t trong t trng u c B vung gc vi mt phng hai khung, B = 3,6.10 -2T. Cho dy dn c tit din 1 mm2, in tr sut =1,5.10-6 m. a. Ngi ta cho t trng gim u xung O trong thi gian t = 10-2 s. Tnh dng in chy qua mch. b. Gi nguyn t trng, m khung cnh b bng cch xoay ngc li, sau dn khung ra thnh hnh vung mi vi cng thi gian. Tnh dng in qua mch lc ny. Bi 437 H thng dy dn t nm ngang nh hnh. Thanh Hz trt trn cch cnh , oy v lun vung gc vi phn gic OH, Hz tip xc vi Oxx, Oy ti M v N. Gc xOy = 2 . Thanh Hz chuyn ng vi vn tc khng i v. Cc dy dn ng cht, cng tit din, c in tr cho mt n v chiu di l r. B qua in tr tip xc ti M, N. H thng t trong t trng u B thng ng, c ln B. Xc nh chiu v ln dng in chy qua MN khi Hz trt u.

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Bi 438 Vng dy trn, bn knh a, in tr 1 n v chiu di r. Mt thanh cng lot trt trn vng trn vi vn tc v. H thng t trong t trng u, B vung gc vi mt phng vng dy nh hnh. Tnh dng in qua khung theo gc . B qua in tr tip xc ti M, N. Bi 439 Cho khung dy dn c kch thc nh hnh, in tr mt n v chiu di l R 0 = 1 /m. Khung t trong t trng u B vung gc mt phng khung. Cho B tng theo quy lut B = kt (k = 10 T/s). Tnh cng dng in qua cc on ca khung. Cho a = 50cm, 2 =1,4. Bi 440 Cho h thng nh hnh v, thanh kim loi MN = l = 20cm, khi lng m = 20g; E = 1,5v, r = 0,1 . Cm ng t B thng ng hng xung, B = 0,4T. Do lc t cn bng vi lc ma st nn thanh MN trt u vi vn tc 5 m/s. Cho in tr ca h thng l R = 0,9 v khng i. Ly g = 10m/s2. a. Tnh ln v chiu dng in trong mch. b. H s ma st gia MN v cc ray. c. dng in chy t N n M vi ln 0,5A th phi ko MN sang pha no? Vn tc v lc ko bao nhiu? Bi 441 Hai thanh kim loi thng ng, in tr khng ng k, hai u ni nhau bng in tr R. Mt thanh kim loi MN = l, khi lng m c th cho trt khng ma st trn hai thanh ng xung di v lun lun nm ngang. H thng t trong t trng u c B vung gc vi mt phng khung nh hnh v. B qua sc cn khng kh. a. Tnh vn tc cc i ca thanh MN. Cho hai thanh ng thng ng di. b. Tnh nh cu a trong trng hp hai thanh ng by gi hp vi phng ngang mt gc . Bi 442 Thay in tr R bng t c in dung C. Tnh gia tc chuyn ng ca thanh MN v cho bit s bin i nng lng trong mch. Bi 443 Thanh ng khi lng m trt trn hai thanh ray t nghing mt gc (tg > k); k l h s ma st gia thanh ng v hai ray. Pha trn hai u thanh ray c ni nhau bng mt in tr R. H thng t trong t trng u c B mt phng ca hai ray. Tnh vn tc ca thanh ng c th t c. Cho khong cch gia hai thanh ray l l; b qua in tr cc phn khc. Bi 444

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Trong bi 443 nu thay R bng t c in dung c. Tm gia tc chuyn ng ca thanh ng. Bi 445 Mt da kim loi c lp, bn knh a quay quanh trc vi vn tc n. Tnh hiu in th gia tm v mp da khi: a. Khng c t trng. b. C t trng u, B mt da. Bi 446 Thanh kim loi khi lng m, quay khng ma st quanh O v trt khng ma st trn mt vng dy kim loi bn knh b. H thng t trong t trng u, B mt phng vng dy. Trc v vng dy ni vi ngun c sut in ng E. a. Tm quy lut ca dng in i thanh quay u vi vn tc gc . b. Sut in ng E ca ngun cn duy tr dng in trn. Cho in tr ton phn ca mch l R v khng i. Bi 447 Hai cun dy c h s t cm L1, L2 c in tr khng ng k mc song song v c ni vi ngun (E, r) qua in tr R (nh hnh). ng K, tm cng dng in n nh trong cc cun dy v qua in tr R. B qua s h cm gia cc cun dy. Bi 448 Cun dy c h s t cm K, in tr khng ng k mc vi t c in dung C nh hnh v. Khi K ng li v dng in qua mch n nh. Tm hiu in th cc i hai u t C sau khi K m. Chn ngun c (E, r). Bi 449 Cun dy h s t cm L, in tr khng ng k mc song song vi in tr R vo mch nh hnh v. u tin K m. Tm in lng chy qua in tr R sau khi ng kho K. Cho ngun c (E, r). Bi 450 Cho mch in nh hnh v. Ban u t C1 c tch in n hiu in th U v K m. T C2 khng tch in. Tm dng in cc i qua cun dy L sau khi ng kho K. Cho C1 = C2 = C, b qua in tr ca cun dy.

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