on tap vat ly lop 11

7/28/2019 on tap vat ly lop 11

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LI NI U

Hin nay, vi b mn Vt L, hnh thc thi trc nghim khchquan c p dng trong cc k thi tt nghip v tuyn sinh i hc,cao ng cho lp 12, cn vi lp 10 v lp 11 th ty theo tng

trng, c trng s dng hnh thc kim tra trc nghim t lun, ctrng s dng hnh thc kim tra trc nghim khch quan, cng ctrng s dng c hai hnh thc ty theo tng chng, tng phn.Tuy nhin d kim tra vi hnh thc g i na th cng cn phi nmvng nhng kin thc c bn mt cch c h thng mi lm tt ccc bi kim tra, bi thi.

gip cc em hc sinh n tp mt cch c h thng nhng kinthc ca chng trnh Vt l lp 11 Ban c bn, gim ti, ti xin

tm tt li phn l thuyt trong sch gio khoa, trong ti liu chunkin thc v tuyn chn ra mt s bi tp t lun v mt s cu trcnghim khch quan theo tng phn trong sch gio khoa, sch bitp v mt s sch tham kho. Hy vng tp ti liu ny s gip chc mt cht g cho cc qu ng nghip trong qu trnh gingdy (c th dng lm ti liu dy t chn, dy ph o) v cc emhc sinh trong qu trnh hc tp, kim tra, thi c.

Ni dung ca tp ti liu c tt c cc chng ca sch gio khoaVt l 11 - Chng trnh c bn. Mi chng l mt phn ca ti liu(ring 2 chng: VI. Khc x nh sng, VII. Mt v cc dng cquang c gp li thnh mt phn l Quang hnh). Mi phn c:

Tm tt l thuyt;Cc cng thc;Bi tp t lun;Trc nghim khch quan.

Cc bi tp t lun trong mi phn u c hng dn gii v ps, cn cc cu trc nghim khch quan trong tng phn th ch cp n, khng c li gii chi tit ( bn c t gii).

D c nhiu c gng trong vic su tm, bin son nhng chcchn trong tp ti liu ny khng trnh khi nhng s sut, thiu st.Rt mong nhn c nhng nhn xt, gp ca cc qu ng nghip,cc bc ph huynh hc sinh, cc em hc sinh v cc bn c chnhsa li thnh mt tp ti liu hon ho hn.

Xin chn thnh cm n.

1


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2


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I. TNH INA. TM TT L THUYT1. Hai loi in tch+ C hai loi in tch: in tch dng (+) v in tch m (-).+ Cc in tch cng du th y nhau, tri du th ht nhau.

+ n v in tch l culng (C).2. S nhim in ca cc vt+ Nhim in do c xt: hai vt khng nhim in khi c xt vinhau th c th lm chng nhim in tri du nhau.+ Nhim in do tip xc: cho thanh kim loi khng nhim inchm vo qu cu nhim in th thanh kim loi nhim in cngdu vi in tch ca qu cu. a thanh kim loi ra xa qu cu ththanh kim loi vn cn nhim in.

+ Nhim in do hng ng: a thanh kim loi khng nhim inn gn qu cu nhim in nhng khng chm vo qu cu, th haiu thanh kim loi s nhim in. u gn qu cu hn nhim intri du vi in tch ca qu cu, u xa hn nhim in cng duvi in tch ca qu cu. a thanh kim loi ra xa qu cu th thanhkim loi tr v trng thi khng nhim in nh lc u.3. nh lut Culng

+ ln ca lc tng tc gia hai in tch im ng yn t lthun vi tch cc ln ca hai in tch v t l nghch vi bnhphng khong cch gia chng.

F = k. 221

.

||

r

qq

; k = 9.109

2

2

C

Nm; l hng s in mi ca mi

trng; trong chn khng (hay gn ng l trong khng kh) th = 1.+ Vc t lc tng tc gia hai in tch im:

C im t trn mi in tch;C phng trng vi ng thng ni hai in tch;C chiu: y nhau nu cng du, ht nhau nu tri du;

C ln: F =2

219

.

||10.9

r

qq

.

+ Lc tng tc gia nhiu in tch im ln mt in tch im:

+++= nFFFF ...21

4. Thuyt electron+ Bnh thng tng i s tt c cc in tch trong nguyn t bngkhng, nguyn t trung ho v in.

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+ Nu nguyn t mt bt electron th tr thnh ion dng; nunguyn t nhn thm electron th tr thnh ion m.+ Khi lng electron rt nh nn linh ng ca electron rt ln.V vy electron d dng bt khi nguyn t, di chuyn trong vt haydi chuyn t vt ny sang vt khc lm cc vt b nhim in.

+ Vt nhim in m l vt tha electron; vt nhim in dng lvt thiu electron.+ Vt dn in l vt cha nhiu in tch t do. Vt cch in (inmi) l vt cha rt t in tch t do. Gii thch hin tng nhim in:- Do c xt hay tip xc m cc electron di chuyn t vt ny sangvt kia.- Do hng ng m cc electron t do s di chuyn v mt pha ca

vt (thc cht y l s phn b li cc electron t do trong vt) lmcho pha d electron tch in m v pha ngc li thiu electron nntch in dng.5. nh lut bo ton in tch+ Mt h c lp v in, ngha l h khng trao i in tch vi cch khc th, tng i s cc in tch trong h l mt hng s.+ Khi cho hai vt tch in q1 v q2 tip xc vi nhau ri tch chng

ra th in tch ca chng s bng nhau v l q /1 = q /2 = 221 qq + .

6. in trng+ in trng l mi trng vt cht tn ti xung quanh cc intch.+ Tnh cht c bn ca in trng l n tc dng lc in ln intch t trong n.+ in trng tnh l in trng do cc in tch ng yn gy ra.+ Vc t cng in trng gy bi mt in tch im:

C im t ti im ta xt;C phng trng vi ng thng ni in tch vi im ta xt;C chiu: hng ra xa in tch nu l in tch dng, hng v

pha in tch nu l in tch m;

C ln: E =2

9

.

||10.9

r

q

.

+ n v cng in trng l V/m.+ Nguyn l chng cht in trng:

nEEEE

+++= ...21 .

4


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+ Lc tc dng ca in trng ln in tch: F= q

E.

+ ng sc in l ng c v trong in trng sao cho hngca tip tuyn ti bt k im no trn ng sc cng trng vihng ca vc t cng in trng ti im .+ Tnh cht ca ng sc:

- Ti mi im trong in trng ta c th v c mt ng scin v ch mt m thi. Cc ng sc in khng ct nhau.

- Cc ng sc in trng tnh l cc ng khng khp kn.- Ni no cng in trng ln hn th cc ng sc in

s c v mau hn (dy hn), ni no cng in trng nhhn th cc ng sc in s c v tha hn.+ Mt in trng m cng in trng ti mi im u bng

nhau gi l in trng u.in trng u c cc ng sc in song song v cch unhau.7. Cng ca lc in in th Hiu in th+ Cng ca lc in tc dng ln mt in tch khng ph thuc vodng ng i ca in tch m ch ph thuc vo im u v imcui ca ng i trong in trng, do ngi ta ni in trngtnh l mt trng th.

AMN = q.E.MN.cos = qEd+ in th ti mt im M trong in trng l i lng c trngring cho in trng v phng din to ra th nng khi t ti mt in tch q. N c xc nh bng thng s gia cng ca lcin tc dng ln q khi q di chuyn t M ra v cc v ln ca q.

VM =q

AM

+ Hiu in th gia hai im M, N trong in trng c trng chokh nng sinh cng ca in trng trong s di chuyn ca mt intch t M n N. N c xc nh bng thng s gia cng ca lcin tc dng ln in tch q trong s di chuyn ca q t M n N v ln ca q.

UMN = VM VN =q

AMN

+ n v hiu in th l vn (V).+ H thc gia cng in trng v hiu in th: E =

d

U.

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+ Ch c hiu in th gia hai im trong in trng mi c gi trxc nh cn in th ti mi im trong in trng th ph thucvo cch chn mc ca in th.8. T in+ T in l mt h hai vt dn t gn nhau v ngn cch nhau bng

mt lp cch in. Mi vt dn gi l mt bn ca t in.+ T in dng cha in tch.+ T in l dng c c dng ph bin trong cc mch in xoaychiu v cc mch v tuyn. N c nhim v tch v phng introng mch in.+ ln in tch trn mi bn ca t in khi tch in gi lin tch ca t in.

+ in dung ca t in C = U

Q

l i lng c trng cho kh nngtch in ca t in mt hiu in th nht nh.+ n v in dung l fara (F).

+ in dung ca t in phng C =d

S

4.10.9 9.

Trong S l din tch ca mi bn (phn i din); d l khongcch gia hai bn v l hng s in mi ca lp in mi chim

y gia hai bn.+ Mi t in c mt hiu in th gii hn. Khi hiu in th giahai bn t vt qu hiu in th gii hn th lp in mi gia haibn t b nh thng, t in b hng.+ Ghp cc t in* Ghp song song:

U = U1 = U2 = = Un;

Q = q1 + q2 + + qn;C = C1 + C2 + + Cn.* Ghp ni tip:

Q = q1 = q2 = = qn;U = U1 + U2 + + Un;

nCCCC

1...

111

21

+++=.

+ Nng lng t in tch in: W =21 QU =

21

CQ

2

=21 CU2.

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B. CC CNG THC

+ Lc tng tc gia hai in tch im: F =2

219

.

||.10.9

r

qq

.

+ Lc tng tc ca nhiu in tch ln mt in tch:

+++=n

FFFF ...2

.

+ Cng in trng gy bi mt in tch im: E =2

9

.

||.10.9

r

q

.

+ Nguyn l chng cht in trng:

+++= nEEEE ...21.

+ Lc in trng tc dng ln in tch im:

= EqF .

+ Cng ca lc in trng: A = q(VB VC) = qUBC.

+ Lin h gia E v U trong in trng u: E =d

U;

Vc t

E hng t ni c in th cao sang ni c in th thp.

+ in dung ca t in C =U

Q.

+ in dung ca t in phng C =d

S

4.10.9 9.

+ Cc t in ghp song song:U = U1 = U2 = = Un;Q = q1 + q2 + + qn;C = C1 + C2 + + Cn;in dung ca b t ghp song song ln hn in dung ca cc t

thnh phn; ghp song song tng in dung ca b t.

+ Cc t in ghp ni tip:Q = q1 = q2 = = qn;U = U1 + U2 + + Un;

nCCCC

1...

111

21

+++=;

in dung ca b t ghp ni tip nh hn in dung ca mi tthnh phn; ghp ni tip tng hiu in th gii hn ca b t.

+ Nng lng t in tch in: W = 21 QU = 21 CQ

2

= 21 CU2.

+ nh l ng nng: W = A.

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C. BI TP T LUN1. Hai qu cu nh ging nhau bng kim loi A v B t trong khngkh, c in tch ln lt l q1 = - 3,2.10-7 C v q2 = 2,4.10-7 C, cchnhau mt khong 12 cm.

a) Xc nh s electron tha, thiu mi qu cu v lc tng tc

in gia chng.b) Cho hai qu cu tip xc in vi nhau ri t v ch c. Xcnh lc tng tc in gia hai qu cu sau .2. Hai in tch q1 v q2 t cch nhau 20 cm trong khng kh, chngy nhau vi mt lc F = 1,8 N. Bit q1 + q2 = - 6.10-6 C v |q1| > |q2|.Xc nh loi in tch ca q1 v q2. V cc vc t lc tc dng cain tch ny ln in tch kia. Tnh q1 v q2.3.Hai in tch q1 v q2 t cch nhau 30 cm trong khng kh, chng

ht nhau vi mt lc F = 1,2 N. Bit q1 + q2 = - 4.10-6 C v |q1| < |q2|.Xc nh loi in tch ca q1 v q2. V cc vc t lc tc dng cain tch ny ln in tch kia. Tnh q1 v q2.4. Hai in tch q1 v q2 t cch nhau 15 cm trong khng kh, chnght nhau vi mt lc F = 4 N. Bit q 1 + q2 = 3.10-6 C; |q1| < |q2|. Xcnh loi in tch ca q1 v q2 . V cc vc t lc tc dng ca intch ny ln in tch kia. Tnh q1 v q2.

5. Hai in tch im c ln bng nhau c t trong khng khcch nhau 12 cm. Lc tng tc gia hai in tch bng 10 N. thai in tch trong du v a chng cch nhau 8 cm th lc tngtc gia chng vn bng 10 N. Tnh ln cc in tch v hng sin mi ca du.6. Cho hai qu cu kim loi nh, ging nhau, tch in v cch nhau20 cm th chng ht nhau mt lc bng 1,2 N. Cho chng tip xcvi nhau ri tch chng ra n khong cch nh c th chng y

nhau vi lc y bng lc ht. Tnh in tch lc u ca mi qucu.7. Ti 2 im A, B cch nhau 10 cm trong khng kh, t 2 in tchq1 = q2 = - 6.10-6 C. Xc nh lc in trng do hai in tch ny tcdng ln in tch q3 = -3.10-8 C t ti C. Bit AC = BC = 15 cm.8. Ti hai im A v B cch nhau 20 cm trong khng kh, t hai intch q1 = -3.10-6C, q2 = 8.10-6C. Xc nh lc in trng tc dngln in tch q3 = 2.10-6C t ti C. Bit AC = 12 cm, BC = 16 cm.9. C hai in tch im q v 4q t cch nhau mt khong r. Cn tin tch th ba Q u v c du nh th no h ba in tchnm cn bng? Xt hai trng hp:

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a) Hai in tch q v 4q c gi c nh.b) hai in tch q v 4q t do.

10. Hai qu cu nh ging nhau bng kim loi, c khi lng 5 g,c treo vo cng mt im O bng hai si dy khng dn, di10 cm. Hai qu cu tip xc vi nhau. Tch in cho mt qu cu th

thy hai qu cu y nhau cho n khi hai dy treo hp vi nhau mtgc 600. Tnh in tch truyn cho qu cu. Ly g = 10 m/s2.11. Hai qu cu nh c cng khi lng m, cng in tch q, ctreo trong khng kh vo cng mt im O bng hai si dy mnh(khi lng khng ng k) cch in, khng co dn, cng chiu dil. Do lc y tnh in chng cch nhau mt khong r (r


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b) Xc nh v tr im M m ti cng in trng tnghp do hai in tch ny gy ra bng 0.18. t 4 in tch c cng ln q ti 4 nh ca mt hnh vungABCD cnh a vi in tch dng t ti A v C, in tch m t tiB v D. Xc nh cng tng hp ti giao im hai ng cho

ca hnh vung.19. t 4 in tch c cng ln q ti 4 nh ca mt hnh vungABCD cnh a vi in tch dng t ti A v D, in tch m t tiB v C. Xc nh cng tng hp ti giao im hai ng choca hnh vung.20. Ti 3 nh ca mt hnh vung cnh a t 3 in tch dng cng ln q. Xc nh cng in trng tng hp do 3 in tch gyra ti nh th t ca hnh vung.

21. Ti 3 nh A, B, C ca mt hnh vung cnh a t 3 in tchdng cng ln q. Trong in tch ti A v C dng, cn intch ti B m. Xc nh cng in trng tng hp do 3 in tchgy ra ti nh D ca hnh vung.22. Hai in tch q1 = q2 = q > 0 t ti hai im A v B trong khngkh cch nhau mt khong AB = 2a. Xc nh vc t cng intrng ti im M nm trn ng trung trc ca on AB v cch

trung im H ca on AB mt on x.23.Hai in tch q1 = - q2 = q > 0 t ti hai im A v B trong khngkh cch nhau mt khong AB = a. Xc nh vc t cng intrng ti im M nm trn ng trung trc ca AB v cch trungim H ca on AB mt khong x.24. A, B, C l ba im to thnh tam gicvung ti A t trong in trng u c E //

BA nh hnh v. Cho = 600; BC = 10 cm vUBC = 400 V.

a) Tnh UAC, UBA v E.b) Tnh cng thc hin dch chuyn in

tch q = 10-9 C t A n B, t B n C v t An C.

c) t thm C mt in tch im q = 9.10 -10 C. Tm cng in trng tng hp ti A.

25. Mt prtn bay trong in trng. Lc prtn im A th vntc ca n bng 2,5.104 m/s. Khi bay n B vn tc ca prtn bngkhng. in th ti A bng 500 V. Tnh in th ti B. Bit prtn ckhi lng 1,67.10-27 kg v c in tch 1,6.10-19 C.

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26. Mt electron di chuyn mt on 0,6 cm, t im M n im Ndc theo mt ng sc in th lc in sinh cng 9,6.10-18 J.

a) Tnh cng m lc in sinh ra khi electron di chuyn tip 0,4 cmt im N n im P theo phng v chiu ni trn.

b) Tnh vn tc ca electron khi n im P. Bit ti M, electron

khng c vn tc ban u. Khi lng ca electron l 9,1.10-31

kg.27. Mt ht bi nh c khi lng m = 0,1 mg, nm l lng trongin trng gia hai bn kim loi phng. Cc ng sc in cphng thng ng v chiu hng t di ln trn. Hiu in thgia hai bn l 120 V. Khong cch gia hai bn l 1 cm. Xc nhin tch ca ht bi. Ly g = 10 m/s2.28. Mt t in phng khng kh c in dung 20 pF. Tch in chot in n hiu in th 250 V.

a) Tnh in tch v nng lng in trng ca t in.b) Sau tho b ngun in ri tng khong cch gia hai bn t

in ln gp i. Tnh hiu in th gia hai bn khi .29. Cho b t c mc nh hnh v. Trong : C 1 = C2 = C3 = 6 F;C4 = 2 F; C5 = 4 F; q4 = 12.10-6 C.

a) Tnh in dung tng ng ca b t.b) Tnh in tch, hiu in th trn tng

t v hiu in th gia hai u on mch.30. Cho b t c mc nh hnh v. Trong C1 = C2 = 2 F; C3 = 3 F; C4 = 6F; C5 =C6 = 5 F. U3 = 2 V. Tnh:a) in dung ca b t.b) Hiu in th v in tch trn tng t.

HNG DN GII

1. a) S electron tha qu cu A: N1 = 19

7

10.6,1

10.2,3

= 2.1012 electron.

S electron thiu qu cu B: N2 = 19

7

10.6,1

10.4,2

= 1,5.1012 electron.

Lc tng tc in gia chng l lc ht v c ln:

F = 9.10

9

2

21 ||

r

qq

= 48.10

-3

N.

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b) Khi cho hai qu cu tip xc vi nhau ri tch ra, in tch ca

mi qu cu l: q1 = q2 = q =2

21 qq + = - 0,4.10-7 C; lc tng tc

in gia chng by gi l lc ht v c ln:

F = 9.109

2

'2

'1 ||

r

qq

= 10-3

N.2. Hai in tch y nhau nn chng cng du; v q1 + q2 < 0 nnchng u l in tch m.

Ta c: F = 9.109 221 ||

r

qq|q1q2| = 9

2

10.9

Fr= 8.10-12; v q1 v q2 cng du

nn |q1q2| = q1q2 = 8.10-12 (1) v q1 + q2 = - 6.10-6 (2). T (1) v (2) tathy q1 v q2 l nghim ca phng trnh:

x2 + 6.10-6x + 8.10-12 = 0

=

=

62

61

10.4

10.2

x

x. Kt qu

=

=

Cq

Cq6

2

61

10.4

10.2hoc

=

=

Cq

Cq6

2

61

10.2

10.4.

V |q1| > |q2|q1 = - 4.10-6 C; q2 = - 2.10-6 C.3. Hai in tch ht nhau nn chng tri du; v q1 + q2 < 0 v |q1|< |q2| nn q1 > 0; q2 < 0.

Ta c: F = 9.109 2 21 || rqq|q1q2| = 9

2

10.9Fr = 12.10-12; v q1 v q2 tri du

nn |q1q2| = - q1q2 = 12.10-12 (1) v q1 + q2 = - 4.10-6 (2). T (1) v (2)ta thy q1 v q2 l nghim ca phng trnh:

x2 + 4.10-6x - 12.10-12 = 0

=

=

62

61

10.6

10.2

x

x. Kt qu

=

=

Cq

Cq6

2

61

10.6

10.2hoc

=

=

Cq

Cq6

2

61

10.2

10.6.

V |q1| < |q2|q1 = 2.10-6 C; q2 = - 6.10-6 C.4. Hai in tch ht nhau nn chng tri du;v q1 + q2 > 0 v |q1| < |q2| nn q1 < 0; q2 > 0.Vc t lc tng tc in gia hai in tch:

Ta c: F = 9.109 221 ||

rqq |q1q2| = 9

2

10.9Fr = 12.10-12; v q1 v q2 tri du

nn |q1q2| = - q1q2 = 12.10-12 (1) v q1 + q2 = - 4.10-6 (2).

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T (1) v (2) ta thy q1 v q2 l nghim ca phng trnh:x2 + 4.10-6x - 12.10-12 = 0

=

=

62

61

10.6

10.2

x

x. Kt qu

=

=

Cq

Cq6

2

61

10.6

10.2hoc

=

=

Cq

Cq6

2

61

10.2

10.6.

V |q1| < |q2|

q1 = 2.10-6

C; q2 = - 6.10-6

C.5. Khi t trong khng kh: |q1| = |q2| = 9

2

10.9

Fr= 4.10-12 C.

Khi t trong du: = 9.109 221 ||

Fr

qq= 2,25.

6. Hai qu cu ht nhau nn chng tch in tri du.V in tch tri du nn:

|q1q2| = - q1q2 = 92

10.9Fr = 1210.

316 q1q2 = -

1210.3

16 (1).

2

21

2

+ qq =

9

2

10.9

Fr= 1210.

9

48 q1 + q2 = 610.

3

192 (2).

T (1) v (2) ta thy q1 v q2 l nghim ca cc phng trnh:3x2 192 .10-6x - 16.10-12 = 0

==

62

61

10.58,510.96,0

xx hoc

==

62

61

10.58,510.96,0

xx

Kt qu:

=

=

Cq

Cq6

2

61

10.58,5

10.96,0hoc

=

=

Cq

Cq6

2

61

10.96,0

10.58,5

=

=

Cq

Cq6

2

61

10.58,5

10.96,0

hoc

=

=

Cq

Cq6

2

61

10.96,0

10.58,5

7. Cc in tch q1 v q2 tc dng ln in tch q3

cc lc

1Fv

2F c phng chiu nh hnh v, c

ln: F1 = F2 = 9.109 231 ||

AC

qq= 72.10-3 N.

Lc tng hp do q1 v q2 tc dng ln q3 l:

F=

1F +

2F ; c phng chiu nh hnh v, c ln:

F = F1cos + F2 cos = 2F1 cos

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= 2.F1.AC

AHAC 22 136.10-3 N.

8. Cc in tch q1 v q2 tc dng ln

in tch q3 cc lc

1Fv

2Fc

phng chiu nh hnh v, c ln:

F1 = 9.109 231 ||

AC

qq= 3,75 N;

F2 = 9.109 232 ||

BC

qq= 5,625 N.

Lc tng hp do q1 v q2 tc dng ln q3 l:

F=

1F+

2F ; c

phng chiu nh hnh v, c ln: F = 222

1 FF + 6,76 N.9. a) Trng hp cc in tch q v 4q c gi c nh: v q v 4qcng du nn cp lc do q v 4q tc dng ln q l cp lc trc ith Q phi nm trn on thng ni im t q v 4q. Gi x l khong

cch t q n Q ta c: 9.109 2||

x

qQ= 9.109 2)(

|4|

xr

qQ

x =

3

r.

Vy Q phi t cch q khong cch3r v cch 4q khong cch

32r

; vi q c ln v du ty .b) Trng hp cc in tch q v 4q t do: ngoi iu kin v

khong cch nh cu a th cn c thm cc iu kin: cp lc do Qv 4q tc dng ln q phi l cp lc trc i, ng thi cp lc do qv Q tc dng ln 4q cng l cp lc trc i. tha mn cc iukin th Q phi tri du vi q v:

9.109.2

3

|.|

r

Qq

= 9.109 2|4.|

r

qqQ = -

9

4q.

10. Khi truyn cho mt qu cu in tch q th do tip xc, mi qu

cu s nhim in tch2

q, chng y nhau v khi v tr cn bng

mi qu cu s chu tc dng ca 3 lc: trng lc P, lc tnh in Fv sc cng si dy T, khi :

14


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tan2

=

P

F=

mgr

q

2

2

9 410.9

q2 =9

2

10.92tan4

mgr . V tan2 =

l

r

2

r = 2ltan2

.

Nn: |q| =9

32

10.9

)2

(tan16

mgl= 4.10-7 C.

11. a) v tr cn bng mi qu cu s chu tc dng ca 3 lc: trng

lc

P, lc tnh in

Fv sc cng si dy

T, khi :

tan =P

F=

mgr

kq2

2

= 2

2

mgr

kq(1).

Mt khc, v r


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= 2E1.AC

AHAC 22 351.103 V/m.

Lc in trng tng hp do q1 v q3 tc dng ln q3 l:

F= q3

E.

V q3 > 0, nn

F cng phng cng chiu vi

E v c ln:

F = |q3|E = 0,7 N.13. Cc in tch q1 v q2 gy ra ti C cc vc t cng in

trng

1E v

2E c phng chiu nh hnh v, c ln:

E1 = E2 = 9.109 21 ||

AC

q= 375.104 V/m.

Cng in trng tng hp ti C do cc

in tch q1 v q2 gy ra l: E=

1E +

2E ; cphng chiu nh hnh v; c ln:

E = E1cos + E2 cos = 2E1 cos

= 2E1.AC

AH 312,5.104 V/m.

Lc in trng tng hp do q1 v q3 tc

dng ln q3

l:

F= q

3

E.

V q3 < 0, nn

F cng phng ngc chiu vi

E v c ln:

F = |q3|E = 0,094 N.14. Tam gic ABC vung ti C. Cc in tch q1 v q2 gy ra ti C cc

vc t cng in trng

1E v

2E c


E1 = 9.109 21||

AC

q= 25.105 V/m;

E2 = 9.109 22 ||

BC

q= 22,5.105 V/m.

Cng in trng tng hp ti C do cc in tch q 1 v q2 gy

ra l: E=

1E +

2E ; c phng chiu nh hnh v; c ln:

E = 22

2

1

EE + 33,6.105 V/m.

Lc in trng tng hp do q1 v q3 tc dng ln q3 l:

F= q3

E.

V q3 < 0, nn

F cng phng ngc chiu vi

E v c ln:16


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F = |q3|E = 0,17 N.15. Tam gic ABC vung ti C. Ccin tch q1 v q2 gy ra ti C cc vc t

cng in trng

1E v

2E c


E1 = 9.109 21 ||

AC

q= 255.104 V/m;

E2 = 9.109 22 ||

BC

q= 600.104 V/m.


ra l: E=

1E +


E = 222

1 EE + 64.105 V/m.

16. a) Cc in tchq1 v q2 gy ra ti Ccc vc t cng

in trng

1E v

2E c phng chiu nh hnh v; c ln:

E1 = 9.1092

1 ||

AC

q= 27.105 V/m; E2 = 9.109

2

2 ||

BC

q= 108.105 V/m.


ra l: E=

1E +


E = E2 E1 = 81.105 V/m.

b) Gi

'1E v

'2E l cng in trng do q1 v q2 gy ra ti M

th cng in trng tng hp do q1 v q2 gy ra ti M l:

E=

'

1E +

'

2E =

0

'

1E = -

'

2E

'

1E v

'

2E phi cng phng,

ngc chiu v bng nhauv ln. tha mn cciu kin th M phi nmtrn ng thng ni A, B; nm ngoi on thng AB v gn q2 hn.

Vi E1 = E2 th 9.109 21 ||

AM

q= 9.109 2

2

)(

||

ABAM

q

||

||

2

1

q

q

ABAM

AM=

= 2AM = 2AB = 30 cm.

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Vy M nm cch A 30 cm v cch B 15 cm; ngoi ra cn c ccim cch rt xa im t cc in tch q 1 v q2 cng c cng in trng bng 0 v cng in trng do cc in tch q 1v q2 gy ra u xp x bng 0.17. a) Cc in tch q1 v q2

gy ra ti C cc vc t cng in trng

1E v

2E c

phng chiu nh hnh v;

c ln: E1 = 9.109 21 ||

AC

q= 9.105 V/m;

E2 = 9.109 22 ||

BC

q= 36.105 V/m.

Cng in trng tng hp ti C do cc in tch q 1 v q2

gy ra l: E=

1E +

2E ; c phng chiu nh hnh v;

c ln: E = E2 + E1 = 45.105 V/m.

b) Gi

'1E v

'2E l cng in trng do q1 v q2 gy ra ti M

th cng in trng tng hp do q1 v q2 gy ra ti M l:

E=

'

1E +

'

2E =

0

'

1E = -

'

2E

'1E v

'2Ephi cng phng, ngc

chiu v bng nhau v ln. thamn cc iu kin th M phi nmtrn ng thng ni A, B; nm trong on thng AB.

Vi E /1 = E/

2 th 9.109

21 ||

AM

q= 9.109 2

2

)(

||

AMAB

q

||

||

2

1

q

q

AMAB

AM=

=

2

3AM =

5

3AB= 12 cm.

Vy M nm cch A 12 cm v cch B 8 cm; ngoi ra cn c ccim cch rt xa im t cc in tch q1v q2 cng c cng in trng bng 0v cng in trng do cc in

tch q1 v q2 gy ra u xp x bng 0.18. Cc in tch t ti cc nh ca hnhvung gy ra ti giao im O ca hai ng

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cho hnh vung cc vc t cng in trng

AE ,

BE ,

CE ,

DE

c phng chiu nh hnh v, c ln:

EA = EB = EC = ED = 22

a

kq

.

Cng in tng tng hp ti O l:E=

AE +

BE +

CE +

DE =

0 ; v

AE +

CE =

0 v

BE +

DE =

0 .

19. Cc in tch t ti cc nh ca hnhvung gy ra ti giao im O ca hai ngcho hnh vung cc vc t cng in

trng

AE ,

BE ,

CE ,

DE ; c phng chiu

nh hnh v, c ln:EA = EB = EC = ED = 2

2

a

kq

.

Cng in tng tng hp ti O l:

E=

AE +

BE +

CE +

DE

C phng chiu nh hnh v; c ln: E = 4EAcos450 = 224

a

kq

.

20. Cc in tch t ti cc nh A, B,C ca hnh vung gy ra ti nh D cahnh vung cc vc t cng in

trng

AE ,

BE ,

CE ; c phng chiu

nh hnh v, c ln:

EA = EC = 2a

kq

; EB = 22 a

kq

.Cng in trng tng hp ti D l:

E=

AE +

BE +

CE ;

c phng chiu nh hnh v; c ln:

E = 2EBcos450 + EA = )122(

2

+kq

.

21. Cc in tch t ti cc nh A, B,C ca hnh vung gy ra ti nh D ca

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hnh vung cc vc t cng in trng

AE ,

BE ,

CE ; c


EB = EC = 2a

kq

; EA = 22 a

kq

.

Cng in trng tng hp ti D l: E= AE + BE +

CE ; cphng chiu nh hnh v; c ln:

E = 2EBcos450 + EA = )122(2

kq

.

22. Cc in tch q1 v q2 gy ra ti M cc vc

t cng in trng

1E v

2E c phng

chiu nh hnh v, c ln:

E1 = E2 = )( 22 xa

kq

+.

Cng in trng tng hp ti M do ccin tch q1 v q2 gy ra l:

E=

1E +

2E ; c phng chiu nh hnh v; c

ln:E = E1cos + E2 cos = 2E1 cos = 2E1. 22 xa

x

+=

( ) 23

22 xa

kqx

+.

23. Cc in tch q1 v q2 gy ra ti M cc

vc t cng in trng

1E v

2E c


E1 = E2 = )( 22 xa kq+ .

Cng in trng tng hp ti M do cc

in tch q1 v q2 gy ra l:

E=

1E +

2E ;

c phng chiu nh hnh v; c ln:E = E1cos + E2 cos = 2E1cos

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21/132

= 2E1. 22 xa

a

+=

( ) 23

22 xa

kqa

+24. a) UAC = E.AC.cos900 = 0.

UBA = UBC + UCA = UBC = 400 V.

E =cos.BCU

BC = 8.103 V/m.

b) AAB = qUAB = -qUBA = -4.10-7 J.ABC = qUBC = 4.10-7 J.AAC = qUAC = 0.

c) in tch q t ti C s gy ra tiA vc t cng in trng

/E c phng chiu nh hnh v; c

ln: E/ = 9.109 2||CAq = 9.109 2)sin.( || BC q = 5,4.10

3 V/m.

Cng in trng tng hp ti A l:

AE =

E +

/E ; c phng

chiu nh hnh v, c ln: EA = 22 'EE + = 9,65.103 V/m.

25. Ta c: W = WB - WA = -2

1mv2 = A = q(VA VB)

VB = VA +q

mv2

2= 503,26 V.

26. a) AMN = q.E.MN E = MNq

AMN.

= - 104 V/m; du - cho bit E

ngc chiu chuyn ng ca electron (c mc nhin chn lmchiu dng); ANP = q.E.NP = 6,4.10-18 J.

b) Ta c: W = WP WM = 21

mv2

P = AMP = AMN + ANP

vp =m

AA NPMN )(2 + = 5,93.106 m/s.

27. Ht bi nm cn bng nn lc in trng cn bng vi trng lc.Lc in trng phi c phng thng ng v hng ln, do ht

bi phi mang in tch dng (lc in

Fcng phng, cng chiu

vi E). Ta c: qE = q dU = mg q =

Umgd = 8,3.10-11 C.

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22/132

28. a) q = CU = 5.10-9 C; W =2

1CU2 = 625.10-9 J.

b) C =kd

S

4; C =

dk

S

24

=

2

C= 10 pF; q = q; U =

'

'

C

q= 500 V.

29. Phn tch on mch: ((C1 nt C2 nt C3) // C4) nt C5.

a) C123 =133221

321

CCCCCCCCC

++ = 2 F; C1234 = C123 + C4 = 4 F;

C =51234

51234

CC

CC

+ = 2 F.

b) U4 = U123 = U1234 =4

4

C

q= 6 V;

q1234 = q5 = Q = C1234U1234 = 24.10-6 C; U5 =5

5

Cq = 6 V;

q123 = q1 = q2 = q3 = C123.U123 = 12.10-6 C;

U1 =1

1

C

q= 2 V = U2 = U3; UAB =

C

Q= 12 V.

30. Phn tch on mch: (((C2 nt C3 nt C4) // C5) nt C1) // C6.

a) C234 =244332

432 CCCCCC

CCC

++ = 1 F; C2345 = C234 + C5 = 6 F;

C12345 =23451

23451

CC

CC

+ = 1,5 F; C = C12345 + C6 = 6,5 F;

b) q3 = q2 = q4 = q234 = C3U3 = 6.10-6 C;

U234 = U5 = U2345 =234

234

C

q= 6 V; q5 = C5U5 = 30.10-6 C;

q2345 = q1 = q12345 = C2345U2345 = 36.10-6 C; U1 =1

1

Cq = 18 V;

U12345 = U6 = UAB =12345

12345

C

q= 24 V; q6 = C6U6 = 120. 10-6 C.

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D. TRC NGHIM KHCH QUAN1. C xt thanh bnit vo ming d, thanh bnit tch in m v

A. Electron chuyn t thanh bnit sang d.B. Electron chuyn t d sang thanh bnit.C. Prtn chuyn t d sang thanh bnit.

D. Prtn chuyn t thanh bnit sang d.2. Hai htbi trong khng kh, mi ht cha 5.108 electron cch nhau2 cm. Lc y tnh in gia hai ht bng

A. 1,44.10-5 N. B. 1,44.10-6 N. C. 1,44.10-7 N. D. 1,44.10-9 N.3. Nu tng khong cch gia hai in tch im ln 3 ln th lctng tc tnh in gia chng s

A. Tng 3 ln. B. Tng 9 ln. C. Gim 9 ln. D. Gim 3 ln.4. Mt thanh bnit khi c xt vi tm d (c hai c lp vi cc vt

khc) th thu c in tch -3.10-8 C. Tm d s c in tchA. -3.10-8 C. B. -1,5.10-8 C. C. 3.10-8 C. D. 0.

5. Lc ht tnh in gia hai in tch l 2.10 -6 N. Khi a chng xanhau thm 2 cm th lc ht l 5.10-7 N. Khong cch ban u giachng l

A. 1 cm. B. 2 cm. C. 3 cm. D. 4 cm.6. Cch biu din lc tng tc gia hai in tch ng yn no sau

y l sai?A. B. C. D.7. Hai in tch im ng yn trong khng kh cch nhau mtkhong r tc dng ln nhau lc c ln bng F. Khi a chng votrong du ho c hng s in mi = 2 v gim khong cch gia

chng cn3

rth ln ca lc tng tc gia chng l

A. 18F. B. 1,5F. C. 6F. D. 4,5F.

8. Haiin tch q1 = q, q2 = -3q t cch nhau mt khong r. Nu intch q1 tc dng ln in tch q2 c ln l F th lc tc dng cain tch q2 ln q1 c ln l

A. F. B. 3F. C. 1,5F. D. 6F.9. Lc tng tc tnh in gia hai in tch im ng yn t cchnhau mt khong 4 cm l F. Nu chng cch nhau 1 cm th lctng tc gia chng l

A. 4F. B. 0,25F. C. 16F. D. 0,5F.

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10. Hai qu cu nh c kch thc ging nhau tch cc in tch l q1= 8.10-6 C v q2 = -2.10-6 C. Cho hai qu cu tip xc vi nhau ri tchng cch nhau trong khng kh cch nhau 10 cm th lc tng tcgia chng c ln l

A. 4,5 N. B. 8,1 N. C. 0.0045 N. D. 81.10-5N.

11. Cu pht biu no sau y ng?A. Electron l ht s cp mang in tch 1,6.10-19 C.B. ln ca in tch nguyn t l 1,6.1019 C.C. in tch ht nhn bng mt s nguyn ln in tch nguyn t.D. Tt c cc ht s cp u mang in tch.

12. a mt thanh kim loi trung ho v in t trn mt gi cchin li gn mt qu cu tch in dng. Sau khi a thanh kim loira tht xa qu cu th thanh kim loi

A. c hai na tch in tri du. B. tch in dng.

C. tch in m.D. trung ho v in.

13. Th nng ca mt electron ti im M trong in trng ca mtin tch im l -3,2.10-19 J. in th ti im M l

A. 3,2 V. B. -3,2 V. C. 2 V. D. -2 V.

14. Hai in tch dng q1 = q v q2 = 4q t ti hai im A, B trongkhng kh cch nhau 12 cm. Gi M l im ti , lc tng hp tcdng ln in tch q0 bng 0. im M cch q1 mt khong

A. 8 cm. B. 6 cm. C. 4 cm. D. 3 cm.15. Cng in trng do in tch +Q gy ra ti im A cch nmt khong r c ln l E. Nu thay bng in tch -2Q v gimkhong cch n A cn mt na th cng in trng ti A c ln l

A. 8E. B. 4E. C. 0,25E. D. E.16. Ti im A trong mt in trng, vc t cng in trngc hng thng ng t trn xung, c ln bng 5 V/m c tin tch q = - 4.10-6 C. Lc tc dng ln in tch q c

A. ln bng 2.10-5N, hng thng ng t trn xung.B. ln bng 2.10-5N, hng thng ng t di ln.C. ln bng 2 N, hng thng ng t trn xung.D. ln bng 4.10-6N, hng thng ng t di ln.

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25/132

17. Mt in tch im Q = - 2.10-7 C, t ti im A trong mi

trng c hng s in mi = 2. Vc t cng in trng E doin tch Q gy ra ti im B vi AB = 6 cm c

A. phng AB, chiu t A n B, ln 2,5.105 V/m.B. phng AB, chiu t B n A, ln 1,5.104 V/m.C. phng AB, chiu t B n A, ln 2,5.105 V/m.D. phng AB, chiu t A n B, ln 2,5.104 V/m.

18. Cng in trng to bi mt in tch im cch n 2 cmbng 105 V/m. Ti v tr cch in tch ny bng bao nhiu th cng in trng bng 4.105 V/m?

A. 2 cm. B. 1 cm. C. 4 cm. D. 5 cm.19. Hai in tch q1 < 0 v

q2 > 0 vi |q2| > |q1| t ti haiim A v B nh hnh v (I ltrung im ca AB). im Mc in trng tng hp dohai in tch ny gy ra bng 0 nm trn

A. AI. B. IB. C. By. D. Ax.20. t 4 in tch c cng ln q ti 4 nh ca mt hnh vungABCD cnh a vi in tch dng ti A v C, in tch m ti B v

D. Cng in trng ti giao im ca hai ng cho ca hnhvung c ln

A. E =2.

24

a

kq

. B. E = 2.

4

a

kq

. C. E =

2.

2

a

kq

. D. E = 0.

21. t hai in tch ti hai im A v B. cng in trngdo hai in tch gy ra ti trung im I ca AB bng 0 th hai intch ny

A. cng dng. B. cng m.C. cng ln v cng du. D. cng ln v tri du.22. Ti 3 nh ca hnh vung cnh a t 3 in tch dng cng ln. Cng in trng do 3 in tch gy ra ti nh th t c ln

A. E = )2

12(

.

.2

a

qk

. B. E = )

2

12(

.

.2

+a

qk

.

C. E = 2.. 2aqk . D. E = 2.2 .3 aqk .

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23. Cu pht biu no sau y cha ng?A. Qua mi im trong in trng ch v c mt ng sc.B. Cc ng sc ca in trng khng ct nhau.C. ng sc ca in trng bao gi cng l ng thng.D. ng sc ca in trng tnh khng khp kn.

24. Qu cu nh khi lng m = 25 g, mang in tch q = 2,5.10-9

Cc treo bi mt si dy khng dn, khi lng khng ng k v

t vo trong mt in trng u vi cng in trng

E c

phng nm ngang v c ln E = 106 V/m. Gc lch ca dy treoso vi phng thng ng l

A. 300. B. 450. C. 600. D. 750.25. Cng ca lc in trng khi mt in tch di chuyn t im M

n im N trong in trng u l A = |q|Ed. Trong d lA. chiu di MN.B. chiu di ng i ca in tch.C. ng knh ca qu cu tch in.D. hnh chiu ca ng i ln phng ca mt ng sc.

26. Mt in tch im di chuyn dc theo ng sc ca mt intrng u c cng in trng E = 1000 V/m, i c mtkhong d = 5 cm. Lc in trng thc hin c cng A = 15.10 -5 J.

ln ca in tch lA. 5.10-6 C. B. 15.10-6 C. C. 3.10-6 C. D. 10-5 C.

27. Mt in tch q = 4.10-6 C dch chuyn trong in trng u ccng in trng E = 500 V/m trn qung ng thng s = 5 cm,to vi hng ca vc t cng in trng gc = 600. Cngca lc in trng thc hin trong qu trnh di chuyn ny v hiuin th gia hai u qung ng ny l

A. A = 5.10-5

J v U = 12,5 V.B. A = 5.10-5 J v U = 25 V.C. A = 10-4 J v U = 25 V.D. A = 10-4 J v U = 12,5 V.

28. Mt electron chuyn ng vi vn tc v 1 = 3.107 m/s bay ra tmt im ca in trng c in th V1 = 6000 V v chy dc theong sc ca in trng n mt im ti vn tc ca electrongim xung bng khng. in th V2 ca in trng ti im l

A. 3441 V. B. 3260 V. C. 3004 V. D. 2820 V.

26


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29. Hai in tch q1 = 2.10-6 C v q2 = - 8.10-6 C ln lt t ti haiim A v B vi AB = 10 cm. Xc nh im M trn ng AB m

ti 2

E = 4 1

E .

A. M nm trong AB vi AM = 2,5 cm.B. M nm trong AB vi AM = 5 cm.C. M nm ngoi AB vi AM = 2,5 cm.D. M nm ngoi AB vi AM = 5 cm.

30. Khi mt in tch q = -2 C di chuyn t im M n im N trongin trng th lc in sinh cng -6 J, hiu in th UMN l

A. 12 V. B. -12 V. C. 3 V. D. -3 V.31. Lc tng tc gia hai in tch q1 = q2 = -3.10-9 C khi t cchnhau 10 cm trong khng kh l

A. 8,1.10-10

N. B. 8,1.10-6

N. C. 2,7.10-10

N. D. 2,7.10-6

N.32. Hai tm kim loi phng t song song, cch nhau 2 cm, nhimin tri du. Mt in tch q = 5.10-9 C di chuyn t tm ny n tmkia th lc in trng thc hin c cng A = 5.10 -8 J. Cng in trng gia hai tm kim loi l

A. 300 V/m. B. 500 V/m. C. 200 V/m. D. 400 V/m.33. Hai in tch im bng nhau t trong chn khng cch nhaumt khong 4 cm th y nhau mt lc l 9.10 -5N. lc y gia

chng l 1,6.10-4N th khong cch gia chng lA. 1 cm. B. 2 cm. C. 3 cm. D. 4 cm.

34. Nu truyn cho qu cu trung ho v in 5.105 electron th qucu mang mt in tch l

A. 8.10-14 C. B. -8.10-14 C. C. -1,6.10-24 C. D. 1,6.10-24 C.35. Hai in tch y nhau mt lc F khi t cch nhau 8 cm. Khi achng v cch nhau 2 cm th lc tng tc gia chng by gi l

A. 0,5F. B. 2F. C. 4F. D. 16F.36. Cho mt hnh thoi tm O, cng in trng ti O trit tiukhi ti bn nh ca hnh thoi t

A. cc in tch cng ln.B. cc in tch cc nh k nhau khc du nhau.C. cc in tch cc nh i din nhau cng du v cng ln.D. cc in tch cng du.

37. Hai qu cu nh ging nhau, c in tch q 1 v q2 khc nhau

khong cch R y nhau vi lc F0. Sau khi chng tip xc, t li khong cch R chng sA. ht nhau vi F < F0. B. ht nhau vi F > F0.

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C. y nhau vi F < F0. D. y nhau vi F > F0.38. Chn cu sai. Cng ca lc in trng lm dch chuyn intch

A. ph thuc vo hnh dng ng i.B. ph thuc vo in trng.

C. ph thuc vo in tch dch chuyn.D. ph thuc vo hiu in th hai u ng i.39. Hai qu cu kim loi ging nhau c treo vo im O bng haisi dy cch in, cng chiu di, khng co dn, c khi lng khngng k. Gi P = mg l trng lng ca mt qu cu, F l lc tngtc tnh in gia hai qu cu khi truyn in tch cho mt qu cu.Khi hai dy treo hp vi nhau gc vi

A. tan = PF

. B. sin = PF

.

C. tan2

=

P

F. D. sin

2

=

F

P.

40. Th cho mt electron khng c vn tc ban u trong mt intrng. Electron s

A. chuyn ng dc theo mt ng sc ca in trng.B. chuyn ng t ni c in th cao sang ni c in th thp.

C. chuyn ngt ni c in th thp sang ni c in th cao.D. ng yn.

41. Th cho mt ion dng khng c vn tc ban u trong mt intrng. Ion dng s

A. chuyn ng dc theo mt ng sc ca in trng.B. chuyn ngt ni c in th cao sang ni c in th thp.C. chuyn ng t ni c in th thp sang ni c in th cao.

D. ng yn.42. Hai qu cu c cng kch thc v cng khi lng, tch cc inlng q1 = 4.10-11 C, q2 = 10-11 C t trong khng kh, cch nhau mtkhong ln hn bn knh ca chng rt nhiu. Nu lc hp dn giachng c ln bng lc y tnh in th khi lng ca mi qucu bng

A. 0,23 kg. B. 0,46 kg. C. 2,3 kg. D. 4,6 kg.43. Hai vin bi st kch thc nh, mang cc in tch q 1 v q2, t

cch nhau mt khong r. Sau cc vin bi c phng in sao choin tch cc vin bi ch cn mt na in tch lc u, ng thi a

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chng n cch nhau mt khong 0,25r th lc tng tc gia chngtng ln

A. 2 ln. B. 4 ln. C. 6 ln. D. 8 ln.44. Mt qu cu tch in +6,4.10-7 C. Trn qu cu tha hay thiubao nhiu electron so vi s prtn qu cu trung ho v in?

A. Tha 4.1012

electron. B. Thiu 4.1012

electron.C. Tha 25.1012 electron. D. Thiu 25.1013 electron.45. Ti A c in tch im q1, ti B c in tch im q2. Ngi tatm c im M ti in trng bng khng. M nm trn onthng ni A, B v gn A hn B. C th ni g v du v ln cacc in tch q1, q2?

A. q1, q2 cng du; |q1| > |q2|. B. q1, q2 khc du; |q1| > |q2|.C. q1, q2 cng du; |q1| < |q2|. D. q1, q2 khc du; |q1| < |q2|.

46. Ti A c in tch im q1, ti B c in tch im q2. Ngi tatm c im M ti in trng bng khng. M nm ngoi onthng ni A, B v gn B hn A. C th ni g v du v ln caq1, q2?

A. q1, q2 cng du; |q1| > |q2|. B. q1, q2 khc du; |q1| > |q2|.C. q1, q2 cng du; |q1| < |q2|. D. q1, q2 khc du; |q1| < |q2|.

47. Mt h c lp gm 3 in tch im c khi lng khng ng k,

nm cn bng vi nhau. Tnh hung no di y c th xy ra?A. Ba in tch cng du nm ba nh ca mt tam gic u.B. Ba in tch cng du nm trn mt ng thng.C. Ba in tch khng cng du nm 3 nh ca mt tam gic

u.D. Ba in tch khng cng du nm trn mt ng thng.

48. Mt electron chuyn ng vi vn tc ban u 106 m/s dc theong sc ca mt in trng u c mt qung ng 1 cm th

dng li. Cng in trng ca in trng u c lnA. 284 V/m. B. 482 V/m. C. 428 V/m. D. 824 V/m.

49. Cng ca lc in tc dng ln in tch im q khi q di chuynt im M n im N trong in trng, khng ph thuc vo

A. v tr ca cc im M, N. B. hnh dng dng i t M n N.C. ln ca in tch q. D. cng in trng ti M v N.

50. Khi mt in tch di chuyn trong mt in trng t mt im An mt im B th lc in sinh cng 2,5 J. Nu th nng ca q ti Al 5 J th th nng ca q ti B l

A. - 2,5 J. B. 2,5 J. C. -7,5 J. D. 7,5J.

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51. Mt electron bay t im M n im N trong mt in trng,gia hai im c hiu in th UMN = 100 V. Cng m lc intrng sinh ra s l

A. 1,6.10-19 J. B. -1,6.10-19 J. C. 1,6.10-17 J. D. -1,6.10-17 J.52. Mt electron chuyn ng dc theo ng sc ca mt in

trng u c cng in trng E = 100 V/m vi vn tc banu 300 km/s theo hng ca vc t

E. Hi electron chuyn ng

c qung ng di bao nhiu th vn tc ca n gim n bngkhng?

A. 1,13 mm. B. 2,26 mm. C. 5,12 mm. D. khng gim.53. Khi mt in tch q = -2.10-6 C di chuyn t im M n im Ntrong in trng th lc in sinh cng -18.10 -6 J. Hiu in th gia

M v N lA. 36 V. B. -36 V. C. 9 V. D. -9 V.54. Mt electron c th khng vn tc ban u st bn m trongin trng u gia hai bn kim loi phng tch in tri du.Cng in trng gia hai bn l 100 V/m. Khong cch giahai bn l 1 cm. Tnh ng nng ca electron khi n n p vobn dng.

A. 1,6.10-17 J. B. 1,6.10-18 J. C. 1,6.10-19 J. D. 1,6.10-20 J.

55. Mt in tch chuyn ng trong in trng theo mt ngcong kn. Gi cng ca lc in trong chuyn ng l A th

A. A > 0 nu q > 0. B. A > 0 nu q < 0.C. A > 0 nu q < 0. D. A = 0.

56. Mt t in phng tch in n hiu in th U1 = 300 V. Saukhi ngt khi ngun in ngi ta gim khong cch gia 2 bn txung cn mt na. Lc ny hiu in th gia hai bn bng

A. 300 V. B. 600 V. C. 150 V. D. 0 V.57. Sau khi ngt t in phng ra khi ngun in, ta tnh tin hai bn khong cch gia chng tng ln hai ln. Khi nng lng intrng trong t s

A. khng i. B. Gim 2 ln. C. tng 2 ln. D. tng 4 ln.58. Mt t in phng khng kh c tch in nu a vo giahai bn mt tm thu tinh c hng s in mi = 3 th

A. Hiu in th gia hai bn khng i.

B. in tch ca t tng gp 3 ln.C. in tch t in khng i.D. in tch ca t gim 3 ln.

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59. Mt t in phng khng kh c in dung C = 2.10 -3 F ctch in n hiu in th U = 500 V. Ngt t ra khi ngun rinhng vo mt cht lng th hiu in th ca t bng U = 250 V.Hng s in mi ca cht lng v in dung ca t lc ny l

A. = 2 v C = 8.10-3 F. B. = 8 v C = 10-3 F.

C. = 4 v C = 2.10-3 F. D. = 2 v C = 4.10-3 F.60. Bn t in nh nhau, mi t c in dung C c ghp ni tipvi nhau. in dung ca b t in bng

A. 4C. B. 2C. C. 0,5C. D. 0,25C.61. Bn t in nh nhau, mi t c in dung C c ghp songsong vi nhau. in dung ca b t in bng

A. 4C. B. 2C. C. 0,5C. D. 0,25C.

62. Chn cu saiA. Khi ni hai bn t vo hai cc ca mt ngun in khng ith hai bn t u mt in tch.

B. Nu t in c tch in th in tch trn hai bn t luntri du v bng nhau v ln.

C. Hai bn t phi c t cch in vi nhau.D. Cc bn ca t in phng phi l nhng tm vt dn phng t

song song v cch in vi nhau vi nhau.

63. Ba t in C1 = 1 F, C2 = 3 F, C3 = 6 F. Cch ghp no sauy cho in dung ca b t l 2,1 F?

A. Ba t ghp ni tip nhau. B. (C1 song song C3) ni tip C2.C. (C2 song song C3) ni tip C1. D. Ba t ghp song song nhau.

64. Mt b t gm 3 t ging nhau ghp song song vi nhau v nivo ngun in khng i c hiu in th 20 V. in dung ca b tbng 1,5 F. in tch trn mi bn t c ln l

A. 10-5

C. B. 9.10-5

C. C. 3.10-5

C. D. 0,5.10-7

C.65. Mt t in c in dung 0,2 F c np in n hiu in th100V. in tch v nng lng ca t in l

A. q = 2.10-5 C ; W = 10-3 J. B. q = 2.105 C ; W = 103 J.C. q = 2.10-5 C ; W = 2.10-4 J. D. q = 2.106 C ; W = 2.104 J.

66. Mt t in phng mc vo hai cc ca mt ngun in c hiuin th 50 V. Ngt t in ra khi ngun ri ko cho khong cchgia hai bn t tng ln gp 2 ln. Hiu in th ca t in khi l

A. 50V. B. 100V. C. 200V. D. 400V

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67. Mt t in c in dung 24 nF c tch in n hiu in th450 V th c bao nhiu electron di chuyn n bn tch in m cat?

A. 6,75.1012. B. 13,3.1012. C. 6,75.1013. D. 13,3.1013.68. Trn v mt t in c ghi 20 F - 200 V. Ni hai bn t in vi

mt hiu in th 120 V. in tch ca t in lA. 12.10-4 C. B. 24.10-4 C. C. 2.10-3 C. D. 4.10-3 C.69. Hai t in cha cng mt in tch th

A. chng phi c cng in dung.B. chng phi c cng hiu in th.C. t in c in dung ln hn s c hiu in th ln hn.D. t in c in dung nh hn s c hiu in th ln hn.

70. T in phng, khng kh c in dung 5 nF. Cng intrng ln nht m t c th chu c l 3.105 V/m, khong cchgia hai bn t l 2 mm. in tch ln nht c th tch c cho t l

A. 2.10-6 C. B. 2,5.10-6 C. C. 3.10-6 C. D. 4.10-6 C.71. Mt in tch q = 3,2.10-19 C chy t im M c in th VM =10 V n im N c in th VN = 5 V. Khong cch t M n N l2 cm. Cng ca lc in trng l

A. 6,4.10-21 J. B. 32.10-19 J. C. 16.10-19 J. D. 32.10-21 J

72. Mt t in phng c in dung 200 pF c tch in di hiuin th 40 V. Khong cch gia hai bn l 0,2 mm. in tch ca tin v cng in trng bn trong t in l

A. q = 5.10-11 C v E = 106 V/m.B. q = 8.10-9 C v E = 2.105 V/m.C. q = 5.10-11 C v E = 2.105 V/m.D. q = 8.10-11 C v E = 106 V/m.

P N1B. 2C. 3C. 4C. 5B. 6B. 7D. 8A. 9C. 10B. 11C. 12D. 13C. 14C. 15A.16B. 17C. 18B. 19D. 20D. 21C. 22B. 23C. 24B. 25D. 26C. 27A. 28A.29B. 30C. 31B. 32B. 33C. 34B. 35D. 36C. 37C. 38A. 39C. 40C. 41B.42A. 43B. 44B. 45C. 46B. 47D. 48A. 49B. 50B. 51D. 52C. 53C. 54C.55D. 56C. 57C. 58C. 59D. 60D. 61A. 62A. 63B. 64A. 65A. 66B. 67C.68B. 69D. 70C. 71C. 72B.

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II. DNG IN KHNG IA. TM TT L THUYT1. Dng in+ Dng in l dng cc in tch dch chuyn c hng.+ Chiu qui c ca dng in l chiu dch chuyn ca cc in tch

dng tc l ngc chiu dch chuyn ca cc electron.+ Cc tc dng ca dng in: dng in c tc dng nhit, tc dngho hc, tc dng t, tc dng c v tc dng sinh l, trong tcdng t l tc dng c trng ca dng in.+ Cng dng in c trng cho tc dng mnh yu ca dngin v c xc nh bng thng s gia in lng q dchchuyn qua tit din thng ca vt dn trong khong thi gian t v

khong thi gian : I = t

q

.Dng in c chiu v cng khng thay i theo thi gian gi

l dng in khng i. Vi dng in khng i ta c: I =t

q.

+ iu kin c dng in trong mt mi trng no l trongmi trng phi c cc in tch t do v phi c mt in trng y cc in tch t do chuyn ng c hng. Trong vt dn inc cc in tch t do nn iu kin c dng in l phi c mthiu in th t vo hai u vt dn in.2. Ngun in+ Ngun in l thit b to ra v duy tr hiu in th nhm duytr dng in trong mch.+ Ngun in c hai cc: cc dng (+) v cc m (-).+ Cc lc l (khc bn cht vi lc in) bn trong ngun in c tc

dng lm cho hai cc ca ngun in c tch in khc nhau v do duy tr hiu in th gia hai cc ca n.+ Sut in ng ca ngun in c trng cho kh nng thc hincng ca ngun in v c o bng cng ca lc l khi lm dchchuyn mt n v in tch dng ngc chiu in trng bn

trong ngun in: E =q

A.

o sut in ng ca ngun ta dng vn k mc vo hai ccca ngun in khi mch ngoi h.+ in tr r ca ngun in c gi l in tr trong ca n.

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3. in nng. Cng sut in+ Lng in nng m mt on mch tiu th khi c dng in chyqua chuyn ha thnh cc dng nng lng khc c o bngcng ca lc in thc hin khi dch chuyn c hng cc in tch.+ Cng sut in ca mt on mch l cng sut tiu th in nng

ca on mch v c tr s bng in nng m on mch tiu thtrong mt n v thi gian, hoc bng tch ca hiu in th gia haiu on mch v cng dng in chy qua on mch .

P =t

A= UI.

+ Nhit lng ta ra trn mt vt dn khi c dng in chy qua t lthun vi in tr ca vt dn, vi bnh phng cng dng inv vi thi gian dng in chy qua vt dn : Q = RI2t.

+ Cng sut ta nhit P vt dn khi c dng in chy qua ctrng cho tc ta nhit ca vt dn v c xc nh bng nhit

lng ta ra vt dn trong mt n v thi gian: P =t

Q= RI2.

+ Cng ca ngun in bng in nng tiu th trong ton mch.Ang = EIt.

+ Cng sut ca ngun in bng cng sut tiu th in nng ca

ton mch: Png =E

I.+ o cng sut in ngi ta dng ot-k. o cng ca dngin, tc l in nng tiu th, ngi ta dng my m in nng haycng t in.

in nng tiu th thng c tnh ra kiloat gi (kWh).1kW.h = 3 600 000J

4. nh lut m i vi ton mch+ Cng dng in chy trong mch kn t l thun vi sut in

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

: I =r+

NR

E.

+ Tch ca cng dng in chy qua mt on mch v in trca n c gi l gim th trn on mch . Sut in ngca ngun in c gi tr bng tng cc gim in th mchngoi v mch trong: E = IRN + Ir.

+ Hin tng on mch xy ra khi ni hai cc ca mt ngun inch bng dy dn c in tr rt nh. Khi on mch, dng in quamch c cng ln v c hi.

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+ nh lut m i vi ton mch hon ton ph hp vi nh lutbo ton v chuyn ha nng lng.

+ Hiu sut ca ngun in: H =E

NU =rR

R

+.

B. CC CNG THC

+ in tr ca dy kim loi hnh tr ng cht: R = Sl .

+ nh lut m cho on mch ch c R:

I =R

Uhay UAB = VA VB = IR.

+ Cc in tr ghp ni tip:I = I1 = I2 = ... = In; U = U1 + U2 + ... + Un; R = R1 + R2 + ... + Rn.

+ Cc in tr ghp song song:I = I1 + I2 + ... + In; U = U1 = U2 = ... = Un;

nRRRR

1...

111

21

+++= .

+ Cng v cng sut ca dng in: A = UIt; P = UI.

+ nh lut Jun Len-x: Q = tR

U2= RI2t.

+ Sut in ng ca ngun in: E = It

A

q

A

= .+ Cng v cng sut ngun in: A = EIt; P = EI.+ Cng sut ca dng c tiu th in ch ta nhit:

P = UI = RI2 =R

U2.

+ nh lut m cho ton mch: I =r+

NR

E.

+ Hiu in th mch ngoi: UN = IR = E Ir

+ Hiu sut ca mch in: H =E

NU =rR

R

+.

+ nh lut m cho cc loi on mch: UAB = I.RAB ei.Vi qui c: trc UAB t du + nu dng in chy t A n

B; du - nu dng in chy t B n A; trc e i t du + nudng in chy qua n i t cc dng sang cc m; trc ei t du nu dng in qua n i t cc m sang cc dng.+ Cc ngun ghp ni tip: eb = e1 + e2 + ... + en ; rb = r1 + r2 + ... + rn.+ Cc ngun ging nhau ghp ni tip: eb = ne; rb = nr.

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+ Cc ngun in ging nhau ghp song song: eb = e; rb =m

r.

+ Cc ngun ging nhau ghp hn hp i xng: eb = ne; rb =m

nr.

Vi m l s nhnh, n l s ngun trong mi nhnh.

+ Ghp xung i: eb = |e1 e2|; rb = r1 + r2.

C. BI TP T LUN1. Cng dng in khng i chy qua dy tc ca mt bng nl 0,64 A.

a) Tnh in lng dch chuyn qua tit din thng ca dy tctrong thi gian mt pht.

b) Tnh s electron dch chuyn qua tit din thng ca dy tctrong khong thi gian ni trn.2. Mt b acquy c sut in ng 6 V, sn ra mt cng l 360 J khiacquy ny pht in.

a) Tnh lng in tch dch chuyn trong acquy.b) Thi gian dch chuyn lng in tch ny l 5 pht. Tnh

cng dng in chy qua acquy khi .3. Mt b acquy c th cung cp dng in 4 A lin tc trong 2 gi

th phi np li.a) Tnh cng dng in m acquy ny c th cung cp lin tc

trong 40 gi th phi np li.b) Tnh sut in ng ca acquy ny nu trong thi gian hot

ng trn y n sn sinh ra mt cng l 172,8 kJ.4. Cho mch in nh hnh v.Trong R1 = R2 = 4 ; R3 = 6 ;

R4 = 3 ; R5 = 10 ; UAB = 24 V.Tnh in tr tng ng ca onmch AB v cng dng inqua tng in tr.5. Cho mch in nh hnh v.Trong R1 = 2,4 ; R3 = 4 ; R2= 14 ; R4 = R5 = 6 ; I3 = 2 A.Tnh in tr tng ng caon mch AB v hiu in th gia hai u cc in tr.

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6. Cho mch in nh hnh v. Trong R1 = R3 = R5 = 3 ; R2 = 8 ; R4 =6 ; U5 = 6 V. Tnh in tr tngng ca on mch AB v cng dng in chy qua tng in tr.

7. Cho mch in nh hnh v. Trong R1 = 8 ; R3 = 10 ; R2 = R4 = R5 =20 ; I3 = 2 A.

Tnh in tr tng ng ca onmch AB, hiu in th v cng dng in trn tng in tr.8. Cho mch in nh hnh v.

Nu t vo AB hiu in th100 V th ngi ta c th ly ra haiu CD mt hiu in th UCD = 40 Vv ampe k ch 1A.

Nu t vo CD hiu in th 60 Vth ngi ta c th ly ra hai u AB hiu in th UAB = 15 V. Coiin tr ca ampe k khng ng k. Tnh gi tr ca mi in tr.9. Cho mch in nh hnh v.

Bit R3 = R4.Nu ni hai u AB vo hiu in th

120 V th cng dng in qua R2 l2 A v UCD = 30 V.

Nu ni 2 u CD vo hiu in th120 V th UAB = 20 V.

Tnh gi tr ca mi in tr.10. Mt ngun in c mc vi mt bin tr. Khi in tr ca bintr l 1,65 th hiu in th gia hai cc ca ngun l 3,3 V, cnkhi in tr ca bin tr l 3,5 th hiu in th gia hai cc cangun l 3,5 V. Tnh sut in ng v in tr trong ca ngun.11. Mt ngun in c sut in ng 12 V v in tr trong 2 .Ni in tr R vo hai cc ca ngun in thnh mch kn th cngsut tiu th trn in tr R bng 16 W. Tnh gi tr ca in tr R vhiu sut ca ngun.

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12. Cho mch in nh hnh v. Trong E = 48 V; r = 0; R1 = 2 ; R2 = 8 ;R3 = 6 ; R4 = 16 . in tr ca ccdy ni khng ng k. Tnh hiu inth gia hai im M v N. Mun o UMN

phi mc cc dng ca vn k vi im no?13. Cho mch in nh hnh v. Trong E= 6 V; r = 0,1 ; R = 11 ; R = 0,9 . Tnhhiu in th nh mc v cng sut nhmc ca bng n, bit n sng bnhthng.14. Cho mch in nh hnh v. Trong

e = 6 V; r = 0,5 ; R1 = R2 = 2 ; R3 = R5= 4 ; R4 = 6 . in tr ca ampe k vca cc dy ni khng ng k. Tmcng dng in qua cc in tr, sch ca ampe k v hiu in th gia haicc ca ngun in.15. Cho mch in nh hnh v. Trong E= 6 V; r = 0,5 ; R1 = 1 ; R2 = R3 = 4 ; R4= 6 . Tnh:

a) Cng dng in trong mch chnh.b) Hiu in th gia hai u R4, R3.c) Cng sut v hiu sut ca ngun in.

16. Cho mch in nh hnh v, trong ngun in c sut in ng e = 6,6 V,in tr trong r = 0,12 ; bng n 1 loi

6 V - 3 W; bng n 2 loi 2,5 V - 1,25 W.a) iu chnh R1 v R2 cho cc bng

n 1 v 2 sng bnh thng. Tnh ccgi tr ca R1 v R2.

b) Gi nguyn gi tr ca R1, iu chnh bin tr R2 n gi tr R2 =1 . Khi sng ca cc bng n thay i nh th no so vitrng hp a?

17. Mt ngun in c sut in ng 6 V, in tr trong 2 , mcvi mch ngoi l mt bin tr R to thnh mt mch kn.a) Tnh R cng sut tiu th ca mch ngoi l 4 W.

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b) Vi gi tr no ca R th cng sut tiu th ca mch ngoi tgi tr cc i. Tnh gi tr cc i .18. Hai ngun c sut in ng e1 = e2 = e, cc in tr trong r1 v r2c gi tr khc nhau. Bit cng sut in ln nht m mi ngun cth cung cp cho mch ngoi l P1 = 20 W v P2 = 30 W. Tnh cng

sut in ln nht m c hai ngun c th cung cp cho mchngoi khi chng mc ni tip v khi chng mc song song.19. Mc in tr R = 2 vo b ngun gm hai pin c sut inng v in tr trong ging nhau. Nu hai pin ghp ni tip thcng dng in qua R l I1 = 0,75 A. Nu hai pin ghp song songth cng dng in qua R l I2 = 0,6 A. Tnh sut in ng vin tr trong ca mi pin.20. Mt ngun in c sut in ng e = 18 V, in tr trong r =6 dng thp sng cc bng n loi 6 V - 3 W.

a) C th mc ti a my bng n cc n u sng bnhthng v phi mc chng nh th no?

b) Nu ch c 6 bng n th phi mc chng th no cc bngn sng bnh thng. Trong cc cch mc cch mc no li hn.21. Cho mch in nh hnh v. Trong e1 =2 V; r1 = 0,1 ; e2 = 1,5 V; r2 = 0,1 ; R = 0,2

in tr ca vn k rt ln. Tnh cng dng in qua e1, e2, R v s ch ca vn k.22. Cho mch in nh hnh v. Trong e1= 18 V; r1 = 4 ; e2 = 10,8 V; r2 = 2,4 ; R1= 1 ; R2 = 3 ; RA = 2 ; C = 2 F. Tnhcng dng in qua e1, e2, s ch caampe k, hiu in th v in tch trn t

in C khi K ng v K m.23. Cho mch in nh hnh v. Bit e1 = 8 V;e3 = 6 V; e2 = 4 V; r1 = r2 = 0,5 ; r3 = 1 ; R1= R3 = 4 ; R2 = 5 . Tnh hiu in th gia2 im A, B v cng dng in qua tngnhnh mch.24. Cho mch in nh hnh v. Trong e1 =55 V; r1 = 0,3

; e2 = 10 V; r2 = 0,4

; e3 =

30 V; r3 = 0,1 ; e4 = 15 V; r4 = 0,2 ; R1 =

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9,5 ; R2 = 19,6 ; R3 = 4,9 . Tnh cng dng in qua ccnhnh.25. Cho mch in nh hnh v. Trong E1 =6 V; E2 = 2 V; r1 = r2 = 0,4 ; n loi 6V - 3 W; R1 = 0,2 ; R2 = 3 ; R3 = 4 ; R4 =

1 . Tnh:a) Cng dng in chy trong mch

chnh.b) Hiu in th gia hai im A v N.

26. Cho mch in nh hnh v. Trong b ngun gm 8 acqui,mi ci c sut in ng e = 2 V, in tr trong r= 0,4 mc thnh 2 nhnh, mi nhnh c 4

ngun mc ni tip; n loi 6 V - 6 W; R1 =0,2 ; R2 = 6 ; R3 = 4 ; R4 = 4 . Tnh:a) Cng dng in chy qua mch chnh.b) Hiu in th gia hai im A v M.

27. Cho mch in nh hnh v. Trong bngun c 5 ngun ging nhau, mi ngun csut in ng e = 2 V, in tr trong r =0,2 mc nh hnh v. n c loi6 V - 12 W; R1 = 2,2 ; R2 = 4 ; R3 = 2 .Tnh UMN v cho bit n c sng bnh thng khng? Ti sao?

HNG DN GII

1. a) q = It = 38,4 C. b) N =e

q= 24.1019 electron.

2. a) q = EA

= 60 C. b) I = t

q= 0,2 A.

3. a) q = It = 28800 C; I ='t

q= 0,2 A.

b) E =q

A= 6 V.

4. Phn tch on mch: R1 nt ((R2 nt R3) // R5) nt R4.

R23 = R2 + R3 = 10 ; R235 =523

523RR RR + = 5 ;

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R = R1 + R235 + R4 = 12 ; I = I1 = I235 = I4 =R

UAB = 2 A;

U235 = U23 = U5 = I235R235 = 10 V;

I5 =5

5

R

U= 1 A; I23 = I2 = I3 =

23

23

R

U= 1 A.

5. Phn tch on mch: R1 nt (R2 // R4) nt (R3 // R5).

R24 =42

42

RR

RR

+ = 4,2 ; R35 = 5353

RR

RR

+ = 2,4 ;

R = R1 + R24 + R35 = 9 ; U3 = U3 = U35 = I3R3 = 8 V;

I35 = I24 = I1 = I =35

35

R

U=

3

10A;

U24 = U2 = U4 = I24R24 = 14 V; U1 = I1R1 = 8 V.6. Phn tch on mch: (R1 nt (R3 // R4) nt R5) // R2.

R34 =43

43

RR

RR

+ = 2 ; R1345 = R1 + R34 + R5 = 8 ;

R =13452

13452

RR

RR

+ = 4 ; I5 = I34 = I1 = I1345 = 55

R

U= 2 A;

U34 = U3 = U4 = I34R34 = 4 V;

I3 =3

3

RU

=34

A; I4 =4

4

RU

=32

A; U1345 = U2 = UAB = I1345R1345 = 16 V;

I2 =2

2

R

U= 2 A.

7. Phn tch on mch: R4 nt (R2 // (R3 nt R5)) // R1.

R35 = R3 + R5 = 30 ; R235 =352

352

RR

RR

+= 12 ;

R4235 = R4 + R235 = 32 ; R =42351

42351

RR

RR

+= 6,4 ; I3 = I5 = I35 = 2 A;

U35 = U2 = U235 = I35R35 = 60 V; I2 =2

2

R

U= 3 A;

I235 = I4 = I4235 =235

235

R

U= 5 A; U4235 = U1 = UAB = I4235R4235 = 160 V;

I1 =1

1

U

U= 20 A.

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8. Trng hp t vo gia A v B hiu in th 100 V th on

mch c (R3 nt R2)// R1, nn I3 = I2 = IA = 1 A; R2 =2I

UCD= 40 ;

UAC = UAB UCD = 60 V; R3 =

3I

UAC= 60 .

Trng hp t vo gia C v D hiu in th 60 V th on mch c(R3 nt R1)// R2. Khi UAC = UCD - UAB = 45 V;

I3 = I1 =3R

UAC= 0,75 A; R1 =

1I

UAB= 20 .

9. Trng hp t vo gia A v B hiu in th 120 V th onmch c ((R3 // R2) nt R4) // R1.

Ta c: R2 =2I

UCD = 15 ; UAC = UAB UCD = 90 V. V R3 = R4

I4 =34

90

RR

UAC = = I2 + I3 = 2 +3

30

R R3 = 30 = R4.

Trng hp t vo gia C v D hiu in th 120 V th on mchc (R1 nt R4) // R2) // R3. Khi UAC = UCD UAB = 100 V;

I4 = I1 = 4R

UAC

= 3

10

A; R1 = 1I

UAB

= 6 .

10. Ta c: I1 =1

1

R

U= 2 =

r+1R

E3,3 + 2r = E (1);

I2 =2

2

R

U= 1 =

r+2R

E3,5 + r = E (2). T (1) v (2)

r = 0,2 ; E = 3,7 V.

11. Ta c: P = I2R =2

+rRE R16 =

4412

2

2

++ RRR

R2 - 5R + 4 = 0R = 4 hoc R = 1 .

Khi H =rR

R

+= 67% hoc H = 33%.

12. Ta c: R =4231

4231 ))((

RRRR

RRRR

+++++

= 6 ; I =rR+

E= 6 A;

UAB = IR = 36 V; I1 = I3 = I13 =31 RR

UAB+ = 4,5 A;

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I2 = I4 = I24 =42 RR

UAB+ = 1,5 A;

UMN = VM VN = VM VA + VA VN = UAN UAM = I2R2 I1R1 = 3 V.V UMN > 0 nn VM > VN do ta phi mc cc dng ca vn k voim M.

13. I =rRR ++

E= 0,5 A; U = IR = 5,5 V; P = I2R = 2,75 W.

14. in tr ca ampe k khng ng k nn mch ngoi gm:R1 nt (R2 // R4) nt (R3 // R5)

Ta c: R = R1 +42

42

RR

RR

+ + 5353

RR

RR

+ = 5,5 ;

I = rR+

E

= 1 A = I1 = I24 = I35;

U24 = U2 = U4 = I24R24 = I2442

42

RR

RR

+ = 1,5 V;

I2 =2

2

R

U= 0,75 A; I4 =

4

4

R

U= 0,25 A;

U35 = U3 = U5 = I35R35 = I3553

53

RR

RR

+= 2 V; I3 =

3

3

R

U= 0,5 A;

I5 =5

5

R

U= 0,5 A; IA = I2 I3 = 0,25 A;

15. a) Chp N vi A ta thy mch ngoi c ((R2 // R3) nt R1) // R4. Do

: R23 =32

32

RR

RR

+ = 2 ; R123 = R1 + R23 = 3 ; R = 41234123

RR

RR

+ = 2 ;

I = rR+E

= 2,4 A.

b) U4 = U123 = UAB = IR = 4,8 A; I123 = I1 = I23 =123

123

R

U= 1,6 A;

U23 = U2 = U3 = I23R23 = 3,2 V.c) Cng sut ca ngun: P = EI = 14,4 W; Hiu sut ca ngun:

H =E

ABU = 0,8 = 80%.

16. Ta c: R1 =1

21

P

U= 12 ; R2 =

2

22

P

U= 5 ;

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a) Cc n 1 v 2 sng bnh thng nn:

U1 = U2R2 = U12R2 = 6 V; I1 =1

1

R

U= 0,5 A;

I2 = I2R2 =

2

2

R

U= 0,5 A; I = I1 + I2 = 1 A; R2R2 =

22

22

R

R

I

U= 12 ; R2

= R2R2 R2 = 7 ; R12R2 =I

U R 221 = 6 ; R =I

e- r = 6,48 ; R1 =

R - R12R2 = 0,48 .b) Khi R2 = 1 : R2R2 = R2 + R2 = 6 ;

R12R2 =122

122

R

R

RR

RR

+ = 4 ;

R = R1 + R12R2 = 4,48 ; I =rR

e+

1,435 A;

U12R2 = U1 = U2R2 = IR12R2 = 5,74 V < 6 V nn n 1 sng yu

hn; I2R2 = I2 = IR2 =22

22

R

R

R

U= 0,96 A >

2

2

U

P= 0,5 A nn n 2 sng

mnh hn.

17. a) Ta c: P = I2

R =

2

+rRE

R4 = 44

62

2

++ RR RR2 - 5R + 4 = 0R = 4 hoc R = 1 .

b) Ta c: P = I2R =2

+rRE

R =

Rr

rR

E2

2

2 ++. V E v r khng

i nn P = Pmax khi (R +R

r2) c gi tr cc tiu, m theo bt ng

thc Csi th (R +R

r2) c gi tr cc tiu khi R =

R

r2R = r = 2 .

Khi Pmax =r4

2E

= 4,5 W.

18. Cng sut cc ai m mi ngun cung cp:

P1 = 1

2

4r

e

; P2 = 2

2

4r

e

21

1

41

e

r

P=

; 22

2

41

e

r

P = .Khi hai ngun mc ni tip cng sut cc i m b ngun cung cp:

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Pnt =)(4

4

21

2

rr

e

+

2122

21

4

1

4

11

PPe

r

e

r

Pnt+=+=

Pnt =21

214

PP

PP

+ = 48 W.

Khi hai ngun mc song song, cng sut cc i m b ngun cung

cp: P// = 2

2

1

2

21

21

2

444 r

e

r

e

rrrr

e+=

+= P1 + P2 = 50 W.

19. Khi mc ni tip ta c: 0,75 =r

e

22

2

+(1).

Khi mc song song ta c: 0,6 = r

e

r

e

+=+ 42

22 (2).

T (1) v (2) ta c r = 1 ; e = 1,5 V.20. in tr v cng dng in nh mc ca mi bng n l:

R =

P

U2= 12 ; I =

U

P= 0,5 A.

a) Gi N l s bng n c thp sng. Khi chng sng bnhthng th cng sut tiu th ca mch ngoi l:P = 3N = UI = (e rI)I = 24I 6I2 6I2 8I + N = 0 (1).

phng trnh c nghim th = 16 2N 0 N 8. Vy s bngn ti a l 8 bng.

Vi N = 8 th phng trnh (1) c nghim kp l I = 2 A.Nu cc bng n c mc thnh m dy, mi dy c n bng th ta

phi c I = mIm = I

I

= 4; n = m

N= 2.

Vy phi mc thnh 4 dy, mi dy c 2 bng.b) Vi N = 6 th phng trnh (1) c 2 nghim: I1 = 1 A v I2 = 3 A.

Vi I1 = 1 A, ta c: m =I

I1= 2; n =

m

N= 3.

Vy phi mc thnh hai dy, mi dy c 3 bng.

Khi in tr mch ngoi: R = 23R = 18 .

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Hiu sut ca mch l: H1 =rR

R

+= 0,75.

Vi I2 = 3 A, ta c: m =I

I2= 6; n =

m

N= 1.

Vy phi mc thnh 6 dy, mi dy c 1 bng n.

Khi in tr mch ngoi: R =6

R = 2.

Hiu sut ca mch l: H2 =rR

R

+= 0,25.

Vy, cch mc thnh hai dy, mi dy gm 3 bng n c li hn.21. Gi s dng in chy trong cc nhnh mch c chiu nh hnhv.Ta c: UAB = I1r1 e1 (1)

UAB = I2r2 e2 (2)UAB = IR (3)I1 + I2 = I (4)

T (1), (2), (3), (4) ta c:0,1I1 + 0I2 + 0,2I = 2 (1)0I1 + 0,1I2 + 0,2I = 1,5 (2)

I1 + I2 I = 0 (3)Gii h (1), (2), (3) ta c I1 = 6 A; I2 = 1 A; I = 7 A. Thay I vo (3),ta c UAB = UV = 1,4 V. V I1 > 0; I2 > 0; I > 0 nn dng in chytrong cc nhnh mch ng nh chiu ta gi s.22. Khi K m, mch ngoi h; s ch ampe k IA = 0; e1 l ngun, e2

l my thu nn I1 = I2 =21

21

rr

ee

+

= 1,125 V;

UAB = UC = I2R2 + e2 = 13,5 V; q = CUC = 27.10-6

C.Khi K ng, gi s dng in chy trong cc nhnh mch c chiunh hnh v.Ta c: UAB = I1r1 e1 (1)

UAB = I2r2 e2 (2)UAB = I(R1 + R2 + RA) (3)I1 + I2 = I (4)

T (1), (2), (3), (4) ta c:

4I1 + 0I2 + 6I = 18 (1)0I1 + 2,4I2 + 6I = 10,8 (2)I1 + I2 I = 0 (3)

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Gii h (1), (2), (3) ta c I1 = 1,8 A; I2 = 0; I = 1,8 A; IA = 1,8 A;UC = UR2 = IR2 = 5,4 V; q = CUC = 10,8.10-6 C.23. Gi s dng in chy trong cc nhnh mch c chiu nh hnhv.Ta c: UAB = I1(r1 + R1) e1 (1)

UAB = I2(r2 + R2) e2 (2)UAB = I3(r3 + R3) e3 (3)I1 + I2 = I3 (4)

T (1), (2), (3), (4) ta c:4,5I1 + 0I2 + 5I3 = 14 (1)0I1 + 5,5I2 + 5I3 = 10 (2)I1 + I2 I3 = 0 (3)

Gii h (1), (2), (3) ta c I1 = 1,30 A; I2 = 0,33 A; I3 = 1,63 A. Thay

I3 vo (3), ta c UAB = 2,15 V. V I1 > 0; I2 > 0; I3 > 0 nn dng inchy trong cc nhnh mch ng nh chiu ta gi s.24. Gi s dng in chy trong cc nhnh mch c chiu nh hnhv.Ta c: UAB = I1(r1 + r4 + R1) e1 + e4 (1)

UAB = I2(r2 + R2) e2 (2)UAB = I3(r3 + R3) e3 (3)

I1 + I3 = I2 (4)T (1), (2), (3), (4) ta c:10I1 + 20I2 + 0I3 = 50 (1)0I1 + 20I2 + 5I3 = 40 (2)I1 I2 + I3 = 0 (3)

Gii h (1), (2), (3) ta c I1 = 1,29 A; I2 = 1,86 A; I3 = 0,57 A. ThayI3 vo (3), ta c UAB = - 12,15 V. V UAB < 0 nn in th im A thphn in th im B; I1 > 0; I2 > 0; I3 > 0 nn dng in chy trong

cc nhnh mch ng nh chiu ta gi s.25. Ta c: Eb = E1 + E2 = 8 V; rb = r1 + r2 = 0,8 ;

R =

P

U2= 12 ; R24 = R2 + R4 = 4 ; R24 =

24

24

RR

RR

+ = 3 ;

R = R1 + R24 + R3 = 7,2 ;

a) I =b

b

rR

E

+

= 1 A.

b) U24 = U = U24 = IR24 = 3 V; I24 = I2 = I4 =24

24

R

U= 0,75 A;

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UMN = VM VN = VM VC + VC VN = UMC + UCN= I(r1 + R1) E1 + I2R2 = 3,15 V.

UMN < 0 cho bit in th im M thp hn in th im N.

26. Ta c: Eb = 4e = 8 V; rb =2

4r= 0,8 ; R =

P

U2= 6 ;

R2 = R2 + R = 12 ; R24 =42

42

RRRR

+ = 3 ;

R = R1+ R24+ R3 = 7,2 ;

a) I =b

b

rR

E

+ = 1 A.

b) U24 = U2 = U4 = IR24 = 3 V; I2 = I2 = I =

R

U

2

2

= 0,25 A;UAN = VA VN = VA VC + VC VN

= UAC + UCN = IR1 + I2R2 = 1,7 V.

27. Ta c: Eb = 3e + 2e = 10 V; rb = 3r +2

2r= 0,8 ;

R =

P

U2= 3 ; R23 = R2 + R3 = 6 ; R23 =

23

23

RR

RR

+ = 2 ;

R = R1 + R23 = 4,2 ;

a) I =b

b

rR

E

+ = 2 A.

b) U23 = U = U23 = IR23 = 4 V; I23 = I2 = I3 =23

23

R

U=

3

2A;

UMN = VM VN = VM VC + VC VN = UMC + UCN

= I(3r + R1) 3e + I2R2 = 2,3 V.U = 4 V < Um = 6 V nn n sng yu hn bnh thng.

D. TRC NGHIM KHCH QUAN1. iu kin c dng in l

A. ch cn c cc vt dn.B. ch cn c hiu in th.C. ch cn c ngun in.D. ch cn duy tr mt hiu in th gia hai u vt dn.

2. in nng tiu th c o bngA. vn k. B. ampe k. C. tnh in k. D. cng t in.

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3. Khi mc cc in tr ni tip vi nhau thnh mt on mch. intr tng ng ca on mch s

A. nh hn in tr thnh phn nh nht trong on mch.B. ln hn in tr thnh phn ln nht trong on mch.C. bng trung bnh cng cc in tr trong on mch.

D. bng tng ca in tr ln nht v nh nht trong on mch.4. Khi mc cc in tr song song vi nhau thnh mt on mch.in tr tng ng ca on mch s

A. nh hn in tr thnh phn nh nht trong on mch.B. ln hn in tr thnh phn ln nht trong on mch.C. bng trung bnh cng cc in tr trong on mch.D. bng tng ca in tr ln nht v nh nht trong on mch.

5. Mt ngun in sut in ng E v in tr trong r c ni vi

mt mch ngoi c in tr tng ng R. Nu R = r thA. dng in trong mch c gi tr cc tiu.B. dng in trong mch c gi tr cc i.C. cng sut tiu th trn mch ngoi l cc tiu.D. cng sut tiu th trn mch ngoi l cc i.

6. in tr R1 tiu th mt cng sut P khi c mc vo mt hiuin th U khng i. Nu mc ni tip vi R1 mt in tr R2 ri

mc vo hiu in th U ni trn th cng sut tiu th bi R1 sA. gim. B. khng thay i.C. tng. D. c th tng hoc gim.

7. Mt dng in 0,8 A chy qua cun dy ca loa phng thanh cin tr 8 . Hiu in th gia hai u cun dy l

A. 0,1 V. B. 5,1 V. C. 6,4 V. D. 10 V.8. in tr R1 tiu th mt cng sut P khi c mc vo mt hiuin th U khng i. Nu mc song song vi R1 mt in tr R2 ri

mc vo hiu in th U ni trn th cng sut tiu th bi R1 sA. gim. B. c th tng hoc gim.C. khng thay i. D. tng.

9. Vic ghp ni tip cc ngun in A. c c b ngun c sut in ng ln hn cc ngun c sn.B. c c b ngun c sut in ng nh hn cc ngun c sn.C. c c b ngun c in tr trong nh hn cc ngun c sn.

D. c c b ngun c in tr trong bng in tr mch ngoi.

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10. Hiu in th gia hai u mt mch in gm 2 in tr 10 v30 ghp ni tip nhau bng 20 V. Cng dng in qua in tr10 l

A. 0,5 A. B. 0,67 A. C. 1 A. D. 2 A.11. Vic ghp song song cc ngun in ging nhau th

A. c c b ngun c sut in ng ln hn cc ngun c sn.B. c c b ngun c sut in ng nh hn cc ngun c sn.C. c c b ngun c in tr trong nh hn cc ngun c sn.D. c c b ngun c in tr trong bng in tr mch ngoi.

12. Mt bp in 115 V - 1 kW b cm nhm vo mng in 230 Vc ni qua cu ch chu c dng in ti a 15 A. Bp in s

A. c cng sut to nhit t hn 1 kW.

B. c cng sut to nhit bng 1 kW.C. c cng sut to nhit ln hn 1 kW.D. n cu ch.

13. Mt bp in 230 V - 1kW b cm nhm vo mng in 115 Vc ni qua cu ch chu c dng in ti a 15 A. Bp in s

A. c cng sut to nhit t hn 1 kW. B. c cng sut to nhit bng 1 kW.

C. c cng sut to nhit ln hn 1 kW.

D. n cu ch.14. Hiu in th trn hai u mt mch in gm 2 in tr 10 v30 ghp ni tip nhau bng 20 V. Hiu in th trn hai u intr 10 l

A. 5 V. B. 10 V. C. 15 V. D. 20 V15. Hai in tr nh nhau c ni song song c in tr tngng bng 2 . Nu cc in tr mc ni tip th in tr tng

ng ca chng bngA. 2 . B. 4 . C. 8 . D.16 .

16. in tr ca hai in tr 10 v 30 ghp song song lA. 5 . B. 7,5 . C. 20 . D. 40 .

17. Hiu in th gia hai u on mch in gm 4 in tr 6 mc ni tip l 12 V. Dng in chy qua mi in tr bng

A. 0,5 A. B. 2 A. C. 8 A. D. 16 A.

18. Hiu in th gia hai u on mch in gm 4 in tr 6 mc song song l 12 V. Dng in chy qua mi in tr bngA. 0,5 A B. 2 A. C. 8 A. D. 16 A.

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19. Mt in tr R1 mc song song vi in tr R2 = 12 ri mcvo mt ngun in c sut in ng 24 V, in tr trong khngng k. Cng dng in qua h l 3 A. Gi tr ca R1 l

A. 8 . B. 12 . C. 24 . D. 36 .20. Cng sut sn ra trn in tr 10 bng 90 W. Hiu in th trn

hai u in tr bngA. 90 V. B. 30 V. C. 18 V. D. 9 V.

21. Ngi ta ct mt on dy dn c in tr R thnh 2 na bngnhau v ghp cc u ca chng li vi nhau. in tr ca on dyi ny bng

A. 2R. B. 0,5R. C. R. D. 0,25R.22. Ti hiu in th 220 V cng sut ca mt bng n bng 100 W.

Khi hiu in th ca mch gim xung cn 110 V, lc cng sutca bng n bngA. 20 W. B. 25 W. C. 30 W. D. 50 W.

23. Khi hai in tr ging nhau mc ni tip vo ngun in U thcng sut tiu th ca chng l 20 W. Nu cc in tr ny c mcsong song v ni vo ngun U ni trn th cng sut tiu th tngcng l

A. 10 W. B. 20 W. C. 40 W. D. 80 W.

24. Cng dng in in khng i chy qua dy tc ca mtbng n l I = 0,273 A. Tnh s electron dch chuyn qua tit dinthng ca dy tc trong mt pht.

A. 1,024.1018. B. 1,024.1019. C. 1,024.1020. D. 1,024.1021.25. in nng bin i hon ton thnh nhit nng dng c haythit b no di y khi chng hot ng?

A. Bng n non. B. Qut in.C. Bn i in. D. Acquy ang np in.

26. Hiu in th gia hai u mt in tr tng ln 3 ln th cng dng in qua in tr

A. tng 3 ln. B. tng 9 ln. C. gim 3 ln. D. gim 9 ln.27. Mt bn i in khi s dng vi hiu in th 220 V th cng dng in chy qua bn i l 5 A. Tnh nhit lng to ra trong 20pht.

A. 132.103 J. B. 132.104 J. C. 132.105 J. D. 132.106 J.

28. Mt acquy c sut in ng 12 V. Tnh cng m acquy ny thchin khi mt electron dch chuyn bn trong acquy t cc dng ticc m ca n.A. 192.10-17 J. B. 192.10-18 J. C. 192.10-19 J. D. 192.10-20 J.

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29. i vi mch in kn gm ngun in vi mch ngoi l intr th cng dng in chy trong mch

A. t l thun vi in tr mch ngoi.B. gim khi in tr mch ngoi tng.C. t l nghch vi in tr mch ngoi.

D. tng khi in tr mch ngoi tng.30. Khi mc in tr R1 = 4 vo hai cc ca ngun in th dngin trong mch c cng I1 = 0,5 A. Khi mc in tr R2 = 10 th dng in trong mch l I2 = 0,25 A. in tr trong r ca ngun l

A. 1 . B. 2 . C. 3 . D. 4 .31. i vi mch in kn gm ngun in vi mch ngoi l intr th hiu in th gia hai cc ca ngun in

A. tng khi in tr mch ngoi tng.B. gim khi in tr mch ngoi tng.C. khng ph thuc vo in tr mch ngoi.D. lc u tng sau gim khi in tr mch ngoi tng.

32. Hiu in th gia hai u mt dy dn l 10 V th cng dng in qua dy dn l 2 A. Nu hiu in th gia hai u dy dn l 15 V th cng dng in qua dy dn l

A. 3

4

A. B. 2

1

A. C. 3 A. D. 3

1

A.33. Chn cu tr li sai. Trong mch in ngun in c tc dng

A. To ra v duy tr mt hiu in th.B. To ra dng in lu di trong mch.C. Chuyn cc dng nng lng khc thnh in nng.D. Chuyn in nng thnh cc dng nng lng khc.

34. Mt in tr R = 4 c mc vo ngun in c sut in ng

1,5 V to thnh mch kn th cng sut to nhit trn in tr nyl 0,36 W. Tnh in tr trong r ca ngun in.A. 1 . B. 2 . C. 3 . D. 4 .

35. Cng ca lc l khi lm dch chuyn in lng q = 1,5 C trongngun in t cc m n cc dng ca n l 18 J. Sut in ngca ngun in l

A. 1,2 V. B. 12 V. C. 2,7 V. D. 27 V.36. Cng sut nh mc ca cc dng c in l

A. Cng sut ln nht m dng c c th t c.B. Cng sut ti thiu m dng c c th t c.C. Cng sut m dng c t c khi hot ng bnh thng.

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D. Cng sut m dng c c th t c bt c lc no.37. Sut in ng ca mt ngun in mt chiu l 4 V. Cng calc l lm di chuyn mt in lng 8 mC gia hai cc bn trongngun in l

A. 0,032 J. B. 0,320 J. C. 0,500 J. D. 500 J.

38. Mt bp in c hiu in th v cng sut nh mc l 220 V v1100 W. in tr ca bp in khi hot ng bnh thng lA. 0,2 . B. 20 . C. 44 . D. 440 .

39. Mt bng n khi mc vo mng in c hiu in th 110 V thcng dng in qua n l 0,5 A v n sng bnh thng. Nus dng trong mng in c hiu in th 220 V th phi mc vi nmt in tr l bao nhiu bng n sng bnh thng?

A. 110 . B. 220 . C. 440 . D. 55 .40. Nhit lng to ra trn dy dn khi c dng in chy qua

A. t l thun vi cng dng in.B. t l thun vi bnh phng cng dng in.C. t l nghch vi bnh phng cng dng in.D. t l thun vi bnh phng in tr ca dy dn.

41. trang tr ngi ta dng cc bng n 12 V - 6 W mc ni tipvo mng in c hiu in th 240 V. cc bng n sng bnh

thng th s bng n phi s dng lA. 2 bng. B. 4 bng. C. 20 bng. D. 40 bng.42. Ngun in c r = 0,2 , mc vi R = 2,4 thnh mch kn, khi hiu in th gia hai u R l 12 V. Sut in ng ca ngun l

A. 11 V. B. 12 V. C. 13 V. D. 14 V.43. Mt ngun in c sut in ng 15 V, in tr trong 0,5 mcvi mch ngoi c hai in tr R1 = 20 v R2 = 30 mc song

song. Cng sut ca mch ngoi lA. 4,4 W. B. 14,4 W. C. 17,28 W. D. 18 W.44. Mt b ngun gm 18 ngun ging nhau, mi ci c sut inng 2 V v in tr trong 0,15 mc thnh 3 dy, mi dy c 6ngun mc ni tip. Sut in ng v in tr trong ca b ngun l

A. 12 V; 0,3 . B. 36 V; 2,7 . C. 12 V; 0,9 . D. 6 V; 0,075 .45. Hai acquy c sut in ng 12 V v 6 V, c in tr trong khngng k mc ni tip vi nhau v mc vi in tr 12 thnh mchkn. Cng dng in chy trong mch l

A. 0,15 A. B. 1 A. C. 1,5 A. D. 3 A.53


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46. Mt acquy sut in ng 6 V in tr trong khng ng k mcvi bng n 6 V - 12 W thnh mch kn. Cng dng in chyqua bng n l

A. 0,5 A. B. 1 A. C. 2 A. D. 4 A.47. S m ca cng t in gia nh cho bit

A. Cng sut in gia nh s dng.B. Thi gian s dng in ca gia nh.C. in nng gia nh s dng.D. S dng c, thit b gia nh s dng.

48. Cng sut ca ngun in c xc nh bngA. Lng in tch m ngun in sinh ra trong mt giy.B. Cng m lc l thc hin c khi ngun in hot ng.C. Cng ca dng in trong mch kn sinh ra trong mt giy.

D. Cng lm dch chuyn mt n v in tch dng.49. Mt acquy c sut in ng 2 V, in tr trong 1 . Ni hai ccca acquy vi in tr R = 9 th cng sut tiu th trn in tr Rl

A. 3,6 W. B. 1,8 W. C. 0,36 W. D. 0,18 W50. Sut in ng ca ngun in l i lng c trng cho

A. kh nng tc dng lc ca ngun in.

B. kh nng thc hin cng ca ngun in.C. kh nng d tr in tch ca ngun in.D. kh nng tch in cho hai cc ca n.

51. t vo hai u in tr R mt hiu in th U th nhit lng tara trn vt dn trong thi gian t l

A. Q = IR2t. B. Q = tR

U2. C. Q = U2Rt. D. Q = 2R

Ut.

52. Hai in tr ging nhau dng mc vo mt hiu in thkhng i. Nu mc chng ni tip vi nhau ri mc vo hiu inth th cng sut tiu th ca chng l 20 W. Nu mc chng songsong ri mc chng vo hiu in th th cng sut tiu th cachng l

A. 5 W. B. 10 W. C. 20 W. D. 80 W.53. Mt ngun in c sut in ng 12 V, in tr trong 2 mcvi mt in tr R = 2 thnh mch kn th cng sut tiu trn R l16 W, gi tr ca in tr R bng

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

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54. Mt mch in kn gm ngun in c in tr trong ng k vimch ngoi l mt bin tr. Khi tng in tr mch ngoi th cng dng in trong mch

A. tng. B. tng t l thun vi in tr mch ngoi.C. gim. D. gim t l nghch vi in tr mch ngoi.

55. Mt ngun in vi sut in ng E, in tr trong r, mc vimt in tr ngoi R = r th cng dng in chy trong mch l I.Nu thay ngun in bng 3 ngun in ging ht n mc ni tipth cng dng in trong mch

A. bng 3I. B. bng 2I. C. bng 1,5I. D. bng 2,5I.56. Mt ngun in c mc vi mt bin tr thnh mch kn. Khiin tr ca bin tr l 1,65 th hiu in th gia hai cc cangun l 3,3 V, cn khi in tr ca bin tr l 3,5 V th hiu in thgia hai cc ca ngun l 3,5 V. Sut in ng v in tr trong cangun l

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

57. Mt ngun in vi sut in ng E, in tr trong r, mc vimt in tr ngoi R = r th cng dng in chy trong mch l I.Nu thay ngun in bng 3 ngun in ging ht n mc song

song th cng dng in trong mchA. vn bng I. B. bng 1,5I. C. bng

3

1I. D. bng 0,5I.

58. Mt b ngun c ba ngun ging nhau mc ni tip. Mch ngoil mt in tr khng i. Nu o hai cc ca mt ngun th

A. gim hiu in th in tr trong ca b ngun khng i.B. cng dng in trong mch gim i hai ln.

C. hiu in th gia hai u in tr mch ngoi gim i ba ln.D. cng sut ta nhit trn mch ngoi gim i bn ln.59. Mt ngun in c sut in ng 6 V v in tr trong 1 thc th cung cp cho mch ngoi mt cng sut ln nht l

A. 3 W. B. 6 W. C. 9 W. D. 12 W.60. C 15 chic pin ging nhau, mi ci c sut in ng 1,5 V vin tr trong 0,6 . Nu em ghp chng thnh ba dy song songmi dy c 5 pin th sut in ng v in tr trong ca b ngun l

A. 7,5 V v 1 . B. 7,5 V v 3 .C. 22,5 V v 9 . D. 15 V v 1 .

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61. Tng chiu di ca dy dn ln hai ln v tng ng knh cady dn ln hai ln th in tr ca dy dn s

A. tng gp i. B. tng gp bn.C. gim mt na. D. gim bn ln.

62. Mt ngun in c sut in ng 6 V v in tr trong 1 th

c th to ra c mt dng in c cng ln nht lA. 2 A. B. 4 A. C. 6 A. D. 8 A.63. Ba bng n loi 6 V - 3 W c mc song song vo hai cc camt ngun in c sut in ng 6 V v in tr trong 1 thcng dng in chy trong ngun in l

A. 0,5 A. B. 1 A. C. 1,2 A. D. 1,5 A.64. Ghp ni tip 3 pin c sut in ng v in tr trong ln lt l2,2 V; 1,1 V; 0,9 V v 0,2

; 0,4

; 0,5

thnh b ngun. Trong

mch c dng in cng 1 A chy qua. in tr mch ngoibng

A. 5,1 . B. 4,5 . C. 3,8 . D. 3,1 .65. Mt c qui c sut in ng e = 6 V, in tr trong r = 0,2 .Khi b chp mch (R = 0) th dng in chy qua c qui s c cng l

A. 20 A. B. 30 A. C. 40 A. D. 50 A.

66. Mt my thu thanh c lp rp thch hp vi mch in 110 Vv tip nhn cng sut 50W. c th s dng trong mng in220 V, th cn phi mc ni tip vi n mt in tr

A. 110 . B. 220 . C. 242 . D. 484.67. Mt bng n dy tc loi 220 V - 100 W c in tr l :

A. 242. B. 484. C. 968. D. 440.68. Du hiu tng qut nht nhn bit dng in l :

A. tc dng ha hc. B. tc dng t.C. tc dng nhit. D. tc dng sinh l.

P N1D. 2D. 3B. 4A. 5D. 6A. 7C. 8C. 9A. 10A. 11C. 12D. 13A. 14A. 15C.16B. 17A. 18B. 19C. 20B. 21D. 22B. 23D. 24B. 25C. 26A. 27B. 28B.29B. 30B. 31B. 32C. 33D. 34A. 35D. 36C. 37A. 38C. 39B. 40B. 41C.42C. 43C. 44A. 45C. 46C. 47C. 48C. 49C. 50B. 51B. 52D. 53B. 54D.55C. 56A. 57B. 58C. 59C. 60A. 61C. 62C. 63C. 64D. 65B. 66C. 67B.68B.

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III. DNG IN TRONG CC MI TRNGA. TM TT L THUYT1. Dng in trong kim loi+ Ht ti in trong kim loi l cc electron t do. Mt ca ccelectron t do trong kim loi rt cao nn kim loi dn in rt tt

+ Bn cht dng in trong kim loi l dng dch chuyn c hngca cc electron di tc dng ca in trng.+ in tr sut ca kim loi tng theo nhit gn ng theo hmbc nht: = 0(1 + (t t0)).+ Chuyn ng nhit ca mng tinh th cn tr chuyn ng ca htti in lm cho in tr kim loi ph thuc vo nhit . n gn00 K, in tr ca kim loi rt nh.+ Vt liu siu dn c in tr t ngt gim n bng 0 khi nhit bng hoc thp hn nhit ti hn T TC.+ Cp nhit in l hai dy kim loi khc bn cht, hai u hn vonhau. Khi nhit hai mi hn T1, T2 khc nhau, trong mch c sutin ng nhit in E = T(T1 T2).2. Dng in trong cht in phn+ Cc dung dch mui, axit, baz hay cc mui nng chy c gil cc cht in phn.

+ Ht ti in trong cht in phn l cc ion dng, ion m b phnli t cc phn t mui, axit, baz.+ Cht in phn khng dn in tt bng kim loi v mt cc iontrong cht in phn nh hn mt cc electron trong kim loi, khilng v kch thc ca cc ion ln hn khi lng v kch thcca cc electron nn tc chuyn ng c hng ca chng nhhn.+ Dng in trong cht in phn l dng ion dng v ion mchuyn ng c hng theo hai chiu ngc nhau trong in trng.+ Hin tng dng cc tan xy ra khi cc anion i ti ant ko ccion kim loi ca in cc vo trong dung dch.+ Khi lng cht thot ra cc ca bnh in phn tnh ra gam:

m = kq =n

A

F

1It; vi F = 96500 C/mol.

+ Dng in trong cht in phn khng ch ti in lng m cn ti

c vt cht i theo. Ti in cc ch c electron c th i tip, cnlng vt cht ng li in cc, gy ra hin tng in phn.

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+ Hin tng in phn c p dng trong cc cng ngh luynkim, ha cht, m in, 3. Dng in trong cht kh+ Ht ti in trong cht kh l cc ion dng, ion m v cc electron,c c do cht kh b ion ho.

+ Dng in trong cht kh l dng chuyn di c hng ca cc iondng theo chiu in trng v cc ion m, cc electron ngcchiu in trng.+ Qu trnh dn in khng t lc ca cht kh xy ra khi ta phidng tc nhn ion ha t bn ngoi to ra ht ti in trong chtkh.+ C bn cch chnh dng in c th to ra ht ti in mi trongcht kh:

- Dng in chy qua cht kh lm nhit kh tng cao, khinphn t kh b ion ha.

- in trng trong cht kh rt ln, khin phn t kh b ion hangay khi nhit thp.

- Catt b dng in nung nng , lm cho n c kh nng pht raelectron. Hin tng ny gi l hin tng pht x nhit electron.

- Catt khng nng nhng b cc ion dng c nng lng ln

p vo lm bt ra cc electron.+ Qu trnh phng in t lc trong cht kh l qu trnh phng invn tip tc gi c khi khng cn tc nhn ion ha tc ng t bnngoi.+ Tia la in l qu trnh phng in t lc hnh thnh trong chtkh khi c in trng mnh lm ion ha cht kh.

Tia la in c th hnh thnh trong khng kh iu kin thng,khi in trng t n ngng vo khong 3.106 V/m.

Tia la in c dng ph bin trong ng c n t hn hpn trong xilanh.+ H quang in l qu trnh phng in t lc hnh thnh khi dngin qua cht kh c th gi c nhit cao ca catt n phtc electron bng hin tng pht x nhit electron.

H quang in c th km theo ta nhit v ta sng rt mnh.H quang in c nhiu ng dng nh hn in, lm n chiu

sng, un chy vt liu, 4. Dng in trong cht bn dn+ Cht bn dn l mt nhm vt liu m tiu biu l gecmani v silic.

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+ in tr sut ca cc cht bn dn c gi tr nm trong khongtrung gian gia kim loi v in mi.+ in tr sut ca cht bn dn ph thuc mnh vo nhit v tpcht.+ Cht bn dn c hai loi ht ti in l electron v l trng.

+ Dng in trong cht bn dn l dng chuyn di c hng ca ccelectron v l trng di tc dng ca in trng.+ Bn dn cha no (tp cht cho) l bn dn loi n, c mt electron rt ln so vi l trng. Bn dn cha axepto (tp cht nhn)l bn dn loi p, c mt l trng rt ln so vi mt electron.+ Lp chuyn tip p-n l ch tip xc gia hai min mang tnh dnin p v n trn mt tinh th bn dn. Dng in ch chy qua clp chuyn tip p-n theo chiu t p sang n, nn lp chuyn tip p-n

c dng lm it bn dn chnh lu dng in xoay chiu.B. CC CNG THC+ S ph thuc ca in tr v in tr sut vo nhit :

R = R0(1 + (t t0)); = 0(1 + (t t0)).+ Sut in ng nhit in: E = T(T2 T1).

+ nh lut Faraay: m =n

A

F

1It; m tnh ra gam th F = 96500 C/mol.

C. BI TP T LUN1.Mt bng n 220 V - 100 W c dy tc lm bng vnfram. Khisng bnh thng th nhit ca dy tc bng n l 20000 C. Xcnh in tr ca bng n khi thp sng v khi khng thp sng. Bitnhit ca mi trng l 200 C v h s nhit in tr ca vnframl = 4,5.10-3 K-1.

2.Mt bng n 220 V - 40 W c dy tc lm bng vnfram. intr ca dy tc bng n 200 C l R0 = 121 . Tnh nhit ca dytc khi bng n sng bnh thng. Cho bit h s nhit in tr cavnfram l = 4,5.10-3 K-1.3. Dy tc ca bng n 220 V - 200 W khi sng bnh thng nhit 25000 C c in tr ln gp 10,8 ln so vi in tr 1000 C. Tmh s nhit in tr v in tr R0 ca dy tc 1000 C.4. nhit t1 = 250 C, hiu in th gia hai cc ca bng n l U1= 20 mV th cng dng in qua n l I1 = 8 mA. Khi sng bnhthng, hiu in th gia hai cc ca bng n l U 2 = 240 V thcng dng in chy qua n l I2 = 8 A. Tnh nhit ca dy

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tc bng n khi n sng bnh thng. Bit h s nhit in tr cady tc lm bng n l = 4,2.10-3 K-1.5. Mt mi hn ca cp nhit in c h s nhit in ng T =65 V/K c t trong khng kh 200 C, cn mi hn kia cnung nng n nhit 3200 C. Tnh sut in ng nhit in ca

cp nhit in .6. Mt mi hn ca cp nhit in nhng vo nc ang tan, mihn kia c nhng vo hi nc si. Dng milivn k o c sutnhit in ng ca cp nhit in l 4,25 mV. Tnh h s nhit inng ca cp nhit in .7. Nhit k in thc cht l mt cp nhit in dng o nhit rt cao hoc rt thp m ta khng th dng nhit k thng thng

o c. Dng nhit k in c h s nhit in ng T = 42 V/K o nhit ca mt l nung vi mt mi hn t trong khng kh 200 C cn mi hn kia t vo l th thy milivn k ch 50,2 mV.Tnh nhit ca l nung.8.Mt b ngun in gm 30 pin mc thnh 3 nhm ni tip, minhm c 10 pin mc song song; mi pin c sut in ng 0,9 V vin tr trong 0,6 . Mt bnh in phn ng dung dch CuSO4 cin tr 205 c mc vo hai cc ca b ngun ni trn. Antca bnh in phn bng ng. Tnh khi lng ng bm vo cattca bnh trong thi gian 50 pht. Bit Cu c A = 64; n = 2.9. Chiu dy ca mt lp niken ph ln mt tm kim loi l h =0,05 mm sau khi in phn trong 30 pht. Din tch mt ph ca tmkim loi l 30 cm2. Xc nh cng dng in chy qua bnh inphn. Bit niken c A = 58, n = 2 v c khi lng ring l =8,9 g/cm3.

10. Mun m ng mt tm st c din tch tng cng 200 cm2

,ngi ta dng tm st lm catt ca mt bnh in phn ng dngdch CuSO4 v ant l mt thanh ng nguyn cht, ri cho dngin c cng I = 10 A chy qua trong thi gian 2 gi 40 pht 50giy. Tm b dy lp ng bm trn mt tm st. Cho bit ng c A= 64; n = 2 v c khi lng ring = 8,9.103 kg/m3.11. Ngi ta dng 36 ngun ging nhau, mi ngun c sut inng 1,5 V, in tr trong 0,9

cung cp in cho mt bnh in

phn ng dung dch ZnSO4 vi cc dng bng km, c in tr R= 3,6 . Hi phi mc hn hp i xng b ngun nh th no dng in qua bnh in phn l ln nht. Tnh lng km bm vo

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catt ca bnh in phn trong thi gian 1 gi 4 pht 20 giy. Bit Znc A = 65; n = 2.12. Cho in nh hnh v. Trong b ngun c n pin mc ni tip,mi pin c sut in ng 1,5 V vin tr trong 0,5 . Mch ngoi

gm cc in tr R1 = 20 ; R2 =9 ; R3 = 2 ; n loi 3V - 3W;Rp l bnh in phn ng dung dchAgNO3, c cc ng bng bc. intr ca ampe k v dy ni khngng k; in tr ca vn k rt ln.Bit ampe k A1 ch 0,6 A, ampe k A2 ch 0,4 A. Tnh:

a) Cng dng in qua bnh in phn v in tr ca bnhin phn.b) S pin v cng sut ca b ngun.c) S ch ca vn k.d) Khi lng bc gii phng catt sau 32 pht 10 giy.e) n c sng bnh thng khng? Ti sao?

13. Cho mch in nh hnh v. Ba ngun inging nhau, mi ci c sut in ng e v in

tr trong r. R1 = 3 ; R2 = 6 ; bnh in phncha dung dch CuSO4 vi cc dng bng ngv c in tr Rp = 0,5 . Sau mt thi gian inphn 386 giy, ngi ta thy khi lng ca bncc lm catt tng ln 0,636 gam.

a) Xc nh cng dng in qua bnh in phn v qua tngin tr.

b) Dng mt vn c in tr rt ln mc vo 2 u A v C ca bngun. Nu b mch ngoi i th vn k ch 20 V. Tnh sut inng v in tr trong ca mi ngunin.14. Cho mch in nh hnh v. Bitngun c sut in ng E = 24 V, intr trong r = 1 ; t in c in dungC = 4 F; n loi 6 V - 6 W; ccin tr c gi tr R1 = 6 ; R2 = 4 ;bnh in phn ng dung dch CuSO4

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v c ant lm bng Cu, c in tr Rp = 2 . B qua i

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