1

BI TP VT L 11 C MINH HIU

LI NI U

Hin nay, vi b mn Vt L, hnh thc thi trc nghim khch quan 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, c trng s dng hnh thc kim tra trc nghim khch quan, cng c trng 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 nm vng nhng kin thc c bn mt cch c h thng mi lm tt c cc bi kim tra, bi thi.

gip cc em hc sinh n tp mt cch c h thng nhng kin thc 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 chun kin thc v tuyn chn ra mt s bi tp t lun v mt s cu trc nghim khch quan theo tng phn trong sch gio khoa, sch bi tp v mt s sch tham kho. Hy vng tp ti liu ny s gip ch c mt cht g cho cc qu ng nghip trong qu trnh ging dy (c th dng lm ti liu dy t chn, dy ph o) v cc em hc sinh trong qu trnh hc tp, kim tra, thi c.

Ni dung ca tp ti liu c tt c cc chng ca sch gio khoa Vt 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 c quang 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 p s, cn cc cu trc nghim khch quan trong tng phn th ch c p n, khng c li gii chi tit ( bn c t gii).

D c nhiu c gng trong vic su tm, bin son nhng chc chn 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 chnh sa li thnh mt tp ti liu hon ho hn.

Xin chn thnh cm n.

I. TNH IN

A. TM TT L THUYT

1. 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 vi nhau th c th lm chng nhim in tri du nhau.

+ Nhim in do tip xc: cho thanh kim loi khng nhim in chm vo qu cu nhim in th thanh kim loi nhim in cng du vi in tch ca qu cu. a thanh kim loi ra xa qu cu th thanh kim loi vn cn nhim in.

+ Nhim in do hng ng: a thanh kim loi khng nhim in n gn qu cu nhim in nhng khng chm vo qu cu, th hai u thanh kim loi s nhim in. u gn qu cu hn nhim in tri du vi in tch ca qu cu, u xa hn nhim in cng du vi in tch ca qu cu. a thanh kim loi ra xa qu cu th thanh kim 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 l thun vi tch cc ln ca hai in tch v t l nghch vi bnh phng khong cch gia chng.

F = k.; k = 9.109 ; ( 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 = .

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

4. Thuyt electron

+ Bnh thng tng i s tt c cc in tch trong nguyn t bng khng, nguyn t trung ho v in.

+ Nu nguyn t mt bt electron th tr thnh ion dng; nu nguyn 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 hay di 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 l vt thiu electron.

+ Vt dn in l vt cha nhiu in tch t do. Vt cch in (in mi) 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 sang vt 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) lm cho pha d electron tch in m v pha ngc li thiu electron nn tch in dng.

5. nh lut bo ton in tch

+ Mt h c lp v in, ngha l h khng trao i in tch vi cc h 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= q= .

6. in trng

+ in trng l mi trng vt cht tn ti xung quanh cc in tch.

+ Tnh cht c bn ca in trng l n tc dng lc in ln in tch 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 = .

+ n v cng in trng l V/m.

+ Nguyn l chng cht in trng: .

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

+ ng sc in l ng c v trong in trng sao cho hng ca tip tuyn ti bt k im no trn ng sc cng trng vi hng 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 sc in 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 nh hn 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 u nhau.

7. Cng ca lc in in th Hiu in th

+ Cng ca lc in tc dng ln mt in tch khng ph thuc vo dng ng i ca in tch m ch ph thuc vo im u v im cui ca ng i trong in trng, do ngi ta ni in trng tnh l mt trng th.AMN = q.E.MN.cos( = qEd

+ in th ti mt im M trong in trng l i lng c trng ring 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 lc in tc dng ln q khi q di chuyn t M ra v cc v ln ca q.

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

UMN = VM VN = + n v hiu in th l vn (V).

+ H thc gia cng in trng v hiu in th: E = .

+ Ch c hiu in th gia hai im trong in trng mi c gi tr xc nh cn in th ti mi im trong in trng th ph thuc vo 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 xoay chiu v cc mch v tuyn. N c nhim v tch v phng in trong mch in.

+ ln in tch trn mi bn ca t in khi tch in gi l in tch ca t in.

+ in dung ca t in C = l i lng c trng cho kh nng tch in ca t in mt hiu in th nht nh.

+ n v in dung l fara (F).

+ in dung ca t in phng C = .

Trong S l din tch ca mi bn (phn i din); d l khong cch 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 gia hai bn t vt qu hiu in th gii hn th lp in mi gia hai bn 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;

.

+ Nng lng t in tch in: W = QU = = CU2.

B. CC CNG THC

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

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

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

+ Nguyn l chng cht in trng: .

+ Lc in trng tc dng ln in tch im: .

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

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

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

+ in dung ca t in C = .

+ in dung ca t in phng C = .

+ 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;

;

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

+ Nng lng t in tch in: W = QU = = CU2.

+ nh l ng nng: (W = A.

C. BI TP T LUN

1. Hai qu cu nh ging nhau bng kim loi A v B t trong khng kh, c in tch ln lt l q1 = - 3,2.10-7 C v q2 = 2,4.10-7 C, cch nhau 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. Xc nh lc tng tc in gia hai qu cu sau .

2. Hai in tch q1 v q2 t cch nhau 20 cm trong khng kh, chng y 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 ca in 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 ca in 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, chng ht nhau vi mt lc F = 4 N. Bit q1 + q2 = 3.10-6 C; |q1| < |q2|. Xc nh loi in tch ca q1 v q2 . V cc vc t lc tc dng ca in tch ny ln in tch kia. Tnh q1 v q2.

5. Hai in tch im c ln bng nhau c t trong khng kh cch nhau 12 cm. Lc tng tc gia hai in tch bng 10 N. t hai in tch trong du v a chng cch nhau 8 cm th lc tng tc gia chng vn bng 10 N. Tnh ln cc in tch v hng s in mi ca du.

6. Cho hai qu cu kim loi nh, ging nhau, tch in v cch nhau 20 cm th chng ht nhau mt lc bng 1,2 N. Cho chng tip xc vi 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 qu cu.

7. Ti 2 im A, B cch nhau 10 cm trong khng kh, t 2 in tch q1 = q2 = - 6.10-6 C. Xc nh lc in trng do hai in tch ny tc dng 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 in tch q1 = -3.10-6C, q2 = 8.10-6C. Xc nh lc in trng tc dng ln 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 t in tch th ba Q u v c du nh th no h ba in tch nm cn bng? Xt hai trng hp:

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, di 10 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 mt gc 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, c treo 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 di l. Do lc y tnh in chng cch nhau mt khong r (r 0 t ti hai im A v B trong khng kh cch nhau mt khong AB = 2a. Xc nh vc t cng in trng 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 khng kh cch nhau mt khong AB = a. Xc nh vc t cng in trng ti im M nm trn ng trung trc ca AB v cch trung im H ca on AB mt khong x.

24. A, B, C l ba im to thnh tam gic vung ti A t trong in trng u c //nh hnh v. Cho ( = 600; BC = 10 cm v UBC = 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 A n 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 vn tc ca n bng 2,5.104 m/s. Khi bay n B vn tc ca prtn bng khng. in th ti A bng 500 V. Tnh in th ti B. Bit prtn c khi lng 1,67.10-27 kg v c in tch 1,6.10-19 C.

26. Mt electron di chuyn mt on 0,6 cm, t im M n im N dc 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 cm t 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 trong in trng gia hai bn kim loi phng. Cc ng sc in c phng thng ng v chiu hng t di ln trn. Hiu in th gia hai bn l 120 V. Khong cch gia hai bn l 1 cm. Xc nh in tch ca ht bi. Ly g = 10 m/s2.

28. Mt t in phng khng kh c in dung 20 pF. Tch in cho t 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 : C1 = 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 = 6(F; 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 = = 2.1012 electron.

S electron thiu qu cu B: N2 = = 1,5.1012 electron.

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

F = 9.109= 48.10-3 N.

b) Khi cho hai qu cu tip xc vi nhau ri tch ra, in tch ca mi qu cu l: q1 = q2 = q = = - 0,4.10-7 C; lc tng tc in gia chng by gi l lc ht v c ln: F = 9.109= 10-3 N.

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

Ta c: F = 9.109( |q1q2| = = 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) ta thy q1 v q2 l nghim ca phng trnh:

x2 + 6.10-6x + 8.10-12 = 0 (. Kt qu hoc .

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( |q1q2| = = 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 (. Kt qu hoc .

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( |q1q2| = = 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 (. Kt qu hoc .

V |q1| < |q2| ( q1 = 2.10-6 C; q2 = - 6.10-6 C.

5. Khi t trong khng kh: |q1| = |q2| = = 4.10-12 C.

Khi t trong du: ( = 9.109= 2,25.

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

V in tch tri du nn:

|q1q2| = - q1q2 = = ( q1q2 = - (1).

= = ( q1 + q2 = ( (2).

T (1) v (2) ta thy q1 v q2 l nghim ca cc phng trnh:

3x2 ( .10-6x - 16.10-12 = 0

( hoc

Kt qu:

hoc

hoc

7. Cc in tch q1 v q2 tc dng ln in tch q3 cc lc v c phng chiu nh hnh v, c ln: F1 = F2 = 9.109= 72.10-3 N.

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

= +; c phng chiu nh hnh v, c ln:

F = F1cos( + F2 cos( = 2F1 cos(

= 2.F1.( 136.10-3 N.

8. Cc in tch q1 v q2 tc dng ln in tch q3 cc lc v c phng chiu nh hnh v, c ln:

F1 = 9.109= 3,75 N;

F2 = 9.109= 5,625 N.

Lc tng hp do q1 v q2 tc dng ln q3 l: = +; c phng chiu nh hnh v, c ln: F = ( 6,76 N.

9. a) Trng hp cc in tch q v 4q c gi c nh: v q v 4q cng du nn cp lc do q v 4q tc dng ln q l cp lc trc i th 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= 9.109( x = .

Vy Q phi t cch q khong cch v cch 4q khong cch ; 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 Q v 4q tc dng ln q phi l cp lc trc i, ng thi cp lc do q v Q tc dng ln 4q cng l cp lc trc i. tha mn cc iu kin th Q phi tri du vi q v:

9.109.= 9.109( Q = - .

10. Khi truyn cho mt qu cu in tch q th do tip xc, mi qu cu s nhim in tch , chng y nhau v khi v tr cn bng mi qu cu s chu tc dng ca 3 lc: trng lc , lc tnh in v sc cng si dy , khi : tan = =

( q2 = . V tan= ( r = 2l tan.

Nn: |q| == 4.10-7 C.

11. a) v tr cn bng mi qu cu s chu tc dng ca 3 lc: trng lc , lc tnh in v sc cng si dy , khi :

tan( = = = (1). Mt khc, v r 0, nn cng phng cng chiu vi 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 v c phng chiu nh hnh v, c ln:

E1 = E2 = 9.109= 375.104 V/m.

Cng in trng tng hp ti C do cc in tch q1 v q2 gy ra l: = +; c phng chiu nh hnh v; c ln:

E = E1cos( + E2 cos( = 2E1 cos(

= 2E1.( 312,5.104 V/m.

Lc in trng tng hp do q1 v q3 tc dng ln q3 l: = q3. V q3 < 0, nn cng phng ngc chiu vi 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 v c phng chiu nh hnh v, c ln:

E1 = 9.109= 25.105 V/m;

E2 = 9.109= 22,5.105 V/m.

Cng in trng tng hp ti C do cc in tch q1 v q2 gy ra l: = +; c phng chiu nh hnh v; c ln:

E = ( 33,6.105 V/m.

Lc in trng tng hp do q1 v q3 tc dng ln q3 l: = q3. V q3 < 0, nn cng phng ngc chiu vi v c ln:

F = |q3|E = 0,17 N.

15. Tam gic ABC vung ti C. Cc in tch q1 v q2 gy ra ti C cc vc t cng in trng v c phng chiu nh hnh v, c ln: E1 = 9.109= 255.104 V/m;

E2 = 9.109= 600.104 V/m.

Cng in trng tng hp ti C do cc in tch q1 v q2 gy ra l: = +; c phng chiu nh hnh v; c ln:

E = ( 64.105 V/m.

16. a) Cc in tch q1 v q2 gy ra ti C cc vc t cng in trng v c phng chiu nh hnh v; c ln:

E1 = 9.109= 27.105 V/m; E2 = 9.109= 108.105 V/m.

Cng in trng tng hp ti C do cc in tch q1 v q2 gy ra l:= +; c phng chiu nh hnh v; c ln:

E = E2 E1 = 81.105 V/m.

b) Gi v 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:

= + = (= -( vphi cng phng, ngc chiu v bng nhau v ln. tha mn cc iu kin th M phi nm trn ng thng ni A, B; nm ngoi on thng AB v gn q2 hn.

Vi E1 = E2 th 9.109= 9.109

( = 2 ( AM = 2AB = 30 cm.

Vy M nm cch A 30 cm v cch B 15 cm; ngoi ra cn c cc im cch rt xa im t cc in tch q1 v q2 cng c cng in trng bng 0 v cng in trng do cc in tch q1 v 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 v c phng chiu nh hnh v;

c ln: E1 = 9.109= 9.105 V/m;

E2 = 9.109= 36.105 V/m.

Cng in trng tng hp ti C do cc in tch q1 v q2 gy ra l: = +; c phng chiu nh hnh v;

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

b) Gi v 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:

= + = (= -

( v phi cng phng, ngc chiu v bng nhau v ln. tha mn cc iu kin th M phi nm trn ng thng ni A, B; nm trong on thng AB.

Vi E = E th 9.109= 9.109

( = ( AM = = 12 cm.

Vy M nm cch A 12 cm v cch B 8 cm; ngoi ra cn c cc im cch rt xa im t cc in tch q1 v q2 cng c cng in trng bng 0 v 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 hnh vung gy ra ti giao im O ca hai ng cho hnh vung cc vc t cng in trng , , , c phng chiu nh hnh v, c ln: EA = EB = EC = ED = .

Cng in tng tng hp ti O l:

= +++= ; v += v += .

19. Cc in tch t ti cc nh ca hnh vung gy ra ti giao im O ca hai ng cho hnh vung cc vc t cng in trng , , , ; c phng chiu nh hnh v, c ln: EA = EB = EC = ED = .

Cng in tng tng hp ti O l:

= +++

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

20. Cc in tch t ti cc nh A, B, C ca hnh vung gy ra ti nh D ca hnh vung cc vc t cng in trng , , ; c phng chiu nh hnh v, c ln:

EA = EC =; EB = .

Cng in trng tng hp ti D l:

= ++;c phng chiu nh hnh v; c ln: E = 2EBcos450 + EA = .

21. Cc in tch t ti cc nh A, B, C ca hnh vung gy ra ti nh D ca hnh vung cc vc t cng in trng , , ; c phng chiu nh hnh v, c ln: EB = EC =; EA = .

Cng in trng tng hp ti D l: = ++; c phng chiu nh hnh v; c ln:

E = 2EBcos450 + EA = .

22. Cc in tch q1 v q2 gy ra ti M cc vc t cng in trng v c phng chiu nh hnh v, c ln: E1 = E2 = .

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

= +; c phng chiu nh hnh v; c ln:

E = E1cos( + E2 cos( = 2E1 cos( = 2E1.= .23. Cc in tch q1 v q2 gy ra ti M cc vc t cng in trng v c phng chiu nh hnh v, c ln: E1 = E2 = .

Cng in trng tng hp ti M do cc in tch q1 v q2 gy ra l: = +; c phng chiu nh hnh v; c ln:

E = E1cos( + E2 cos( = 2E1cos(

= 2E1.=

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

UBA = UBC + UCA = UBC = 400 V.

E = = 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 ti A vc t cng in trng c phng chiu nh hnh v; c ln: E/ = 9.109= 9.109= 5,4.103 V/m.

Cng in trng tng hp ti A l: = + ; c phng chiu nh hnh v, c ln: EA = = 9,65.103 V/m.

25. Ta c: (W = WB - WA = - mv2 = A = q(VA VB)

(VB = VA + = 503,26 V.

26. a) AMN = q.E.MN ( E = = - 104 V/m; du - cho bit ngc chiu chuyn ng ca electron (c mc nhin chn lm chiu dng); ANP = q.E.NP = 6,4.10-18 J.

b) Ta c: (W = WP WM = mv = AMP = AMN + ANP

( vp = = 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 cng phng, cng chiu vi ). Ta c: qE = q = mg ( q = = 8,3.10-11 C.

28. a) q = CU = 5.10-9 C; W = CU2 = 625.10-9 J.

b) C = ; C = = = 10 pF; q = q; U = = 500 V.

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

a) C123 = = 2 (F; C1234 = C123 + C4 = 4 (F;

C = = 2 (F.

b) U4 = U123 = U1234 = = 6 V;

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

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

U1 = = 2 V = U2 = U3; UAB = = 12 V.

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

a) C234 = = 1 (F; C2345 = C234 + C5 = 6 (F;

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

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

U234 = U5 = U2345 = = 6 V; q5 = C5U5 = 30.10-6 C;

q2345 = q1 = q12345 = C2345U2345 = 36.10-6 C; U1 = = 18 V;

U12345 = U6 = UAB = = 24 V; q6 = C6U6 = 120. 10-6 C.

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 ht bi trong khng kh, mi ht cha 5.108 electron cch nhau 2 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 lc tng 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 tch

A. -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 xa nhau thm 2 cm th lc ht l 5.10-7 N. Khong cch ban u gia chng 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 mt khong r tc dng ln nhau lc c ln bng F. Khi a chng vo trong du ho c hng s in mi ( = 2 v gim khong cch gia chng cn th ln ca lc tng tc gia chng l

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

8. Hai in tch q1 = q, q2 = -3q t cch nhau mt khong r. Nu in tch q1 tc dng ln in tch q2 c ln l F th lc tc dng ca in 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 cch nhau mt khong 4 cm l F. Nu chng cch nhau 1 cm th lc tng tc gia chng l

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

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 t chng cch nhau trong khng kh cch nhau 10 cm th lc tng tc gia chng c ln l

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

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 cch in li gn mt qu cu tch in dng. Sau khi a thanh kim loi ra 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 mt in 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 trong khng kh cch nhau 12 cm. Gi M l im ti , lc tng hp tc dng 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 n mt khong r c ln l E. Nu thay bng in tch -2Q v gim khong 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 trng c hng thng ng t trn xung, c ln bng 5 V/m c t in tch q = - 4.10-6 C. Lc tc dng ln in tch q c

A. ln bng 2.10-5 N, hng thng ng t trn xung.

B. ln bng 2.10-5 N, hng thng ng t di ln.

C. ln bng 2 N, hng thng ng t trn xung.

D. ln bng 4.10-6 N, hng thng ng t di ln.

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 do in 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 cm bng 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 hai im A v B nh hnh v (I l trung im ca AB). im M c in trng tng hp do hai 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 vung ABCD 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 hnh vung c ln

A. E = . B. E = .C. E = .D. E = 0.

21. t hai in tch ti hai im A v B. cng in trng do hai in tch gy ra ti trung im I ca AB bng 0 th hai in tch 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 = .B. E = .

C. E = .D. E = .

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 C c treo bi mt si dy khng dn, khi lng khng ng k v t vo trong mt in trng u vi cng in trng c phng nm ngang v c ln E = 106 V/m. Gc lch ca dy treo so 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 l

A. 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 in trng u c cng in trng E = 1000 V/m, i c mt khong d = 5 cm. Lc in trng thc hin c cng A = 15.10-5 J. ln ca in tch l

A. 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 c cng in trng E = 500 V/m trn qung ng thng s = 5 cm, to vi hng ca vc t cng in trng gc ( = 600. Cng ca lc in trng thc hin trong qu trnh di chuyn ny v hiu in 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 v1 = 3.107 m/s bay ra t mt im ca in trng c in th V1 = 6000 V v chy dc theo ng sc ca in trng n mt im ti vn tc ca electron gim xung bng khng. in th V2 ca in trng ti im l

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

29. Hai in tch q1 = 2.10-6 C v q2 = - 8.10-6 C ln lt t ti hai im A v B vi AB = 10 cm. Xc nh im M trn ng AB m ti = 4.

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 trong in 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 cch nhau 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, nhim in tri du. Mt in tch q = 5.10-9 C di chuyn t tm ny n tm kia 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 nhau mt khong 4 cm th y nhau mt lc l 9.10-5 N. lc y gia chng l 1,6.10-4 N th khong cch gia chng l

A. 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 qu cu 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 a chng 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 tiu khi 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 q1 v q2 khc nhau khong cch R y nhau vi lc F0. Sau khi chng tip xc, t li khong cch R chng s

A. ht nhau vi F < F0.B. ht nhau vi F > F0.

C. y nhau vi F < F0.D. y nhau vi F > F0.

38. Chn cu sai. Cng ca lc in trng lm dch chuyn in tch

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 hai si dy cch in, cng chiu di, khng co dn, c khi lng khng ng k. Gi P = mg l trng lng ca mt qu cu, F l lc tng tc 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( = .

B. sin( = .

C. tan= . D. sin= .

40. Th cho mt electron khng c vn tc ban u trong mt in trng. 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 ng t 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 in trng. Ion dng 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 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 in lng q1 = 4.10-11 C, q2 = 10-11 C t trong khng kh, cch nhau mt khong ln hn bn knh ca chng rt nhiu. Nu lc hp dn gia chng c ln bng lc y tnh in th khi lng ca mi qu cu 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 q1 v q2, t cch nhau mt khong r. Sau cc vin bi c phng in sao cho in tch cc vin bi ch cn mt na in tch lc u, ng thi a chng n cch nhau mt khong 0,25r th lc tng tc gia chng tng 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 thiu bao 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 ta tm c im M ti in trng bng khng. M nm trn on thng ni A, B v gn A hn B. C th ni g v du v ln ca cc 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 ta tm c im M ti in trng bng khng. M nm ngoi on thng ni A, B v gn B hn A. C th ni g v du v ln ca 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|.

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 theo ng sc ca mt in trng u c mt qung ng 1 cm th dng li. Cng in trng ca in trng u c ln

A. 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 chuyn t 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 A n mt im B th lc in sinh cng 2,5 J. Nu th nng ca q ti A l 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.

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 in trng 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 ban u 300 km/s theo hng ca vc t . Hi electron chuyn ng c qung ng di bao nhiu th vn tc ca n gim n bng khng?

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 N trong in trng th lc in sinh cng -18.10-6 J. Hiu in th gia M v N l

A. 36 V.B. -36 V.C. 9 V.D. -9 V.

54. Mt electron c th khng vn tc ban u st bn m trong in trng u gia hai bn kim loi phng tch in tri du. Cng in trng gia hai bn l 100 V/m. Khong cch gia hai bn l 1 cm. Tnh ng nng ca electron khi n n p vo bn 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 ng cong 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. Sau khi ngt khi ngun in ngi ta gim khong cch gia 2 bn t xung 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 in trng 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 gia hai 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.

59. Mt t in phng khng kh c in dung C = 2.10-3 (F c tch in n hiu in th U = 500 V. Ngt t ra khi ngun ri nhng 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 tip vi 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 song song vi nhau. in dung ca b t in bng

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

62. Chn cu sai

A. Khi ni hai bn t vo hai cc ca mt ngun in khng i th hai bn t u mt in tch.

B. Nu t in c tch in th in tch trn hai bn t lun tri 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 sau y 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 ni vo ngun in khng i c hiu in th 20 V. in dung ca b t bng 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 th 100V. 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 hiu in th 50 V. Ngt t in ra khi ngun ri ko cho khong cch gia hai bn t tng ln gp 2 ln. Hiu in th ca t in khi l

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

67. Mt t in c in dung 24 nF c tch in n hiu in th 450 V th c bao nhiu electron di chuyn n bn tch in m ca t?

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 l

A. 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 in trng ln nht m t c th chu c l 3.105 V/m, khong cch gia 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 l 2 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 hiu in th 40 V. Khong cch gia hai bn l 0,2 mm. in tch ca t in 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 N

1B. 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.II. DNG IN KHNG IA. TM TT L THUYT

1. 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 dng ho hc, tc dng t, tc dng c v tc dng sinh l, trong tc dng t l tc dng c trng ca dng in.

+ Cng dng in c trng cho tc dng mnh yu ca dng in v c xc nh bng thng s gia in lng (q dch chuyn qua tit din thng ca vt dn trong khong thi gian (t v khong thi gian : I = .

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 = .

+ iu kin c dng in trong mt mi trng no l trong mi 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 in c cc in tch t do nn iu kin c dng in l phi c mt hiu 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 duy tr 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 hin cng ca ngun in v c o bng cng ca lc l khi lm dch chuyn mt n v in tch dng ngc chiu in trng bn trong ngun in: E = .

o sut in ng ca ngun ta dng vn k mc vo hai cc ca ngun in khi mch ngoi h.

+ in tr r ca ngun in c gi l in tr trong ca n.

3. in nng. Cng sut in+ Lng in nng m mt on mch tiu th khi c dng in chy qua chuyn ha thnh cc dng nng lng khc c o bng cng 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 th trong mt n v thi gian, hoc bng tch ca hiu in th gia hai u on mch v cng dng in chy qua on mch .

P = = UI.

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

+ Cng sut ta nhit P vt dn khi c dng in chy qua c trng 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 = = 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 = EI.

+ o cng sut in ngi ta dng ot-k. o cng ca dng in, tc l in nng tiu th, ngi ta dng my m in nng hay cng 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 = .

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

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

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

+ Hiu sut ca ngun in: H = = .

B. CC CNG THC+ in tr ca dy kim loi hnh tr ng cht: R = (.

+ nh lut m cho on mch ch c R:

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

+ nh lut Jun Len-x: Q = = RI2t.

+ Sut in ng ca ngun in: E = .

+ Cng v cng sut ngun in: A = EIt; P = EI.

+ Cng sut ca dng c tiu th in ch ta nhit: P = UI = RI2 = .

+ nh lut m cho ton mch: I = .

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

+ Hiu sut ca mch in: H = = .

+ 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 ei t du + nu dng 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.

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

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

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 LUN

1. Cng dng in khng i chy qua dy tc ca mt bng n l 0,64 A.

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

b) Tnh s electron dch chuyn qua tit din thng ca dy tc trong khong thi gian ni trn.

2. Mt b acquy c sut in ng 6 V, sn ra mt cng l 360 J khi acquy 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 on mch AB v cng dng in qua 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 ca on mch AB v hiu in th gia hai u cc in tr.

6. Cho mch in nh hnh v. Trong R1 = R3 = R5 = 3 (; R2 = 8 (; R4 = 6 (; U5 = 6 V. Tnh in tr tng ng 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 on mch 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 th 100 V th ngi ta c th ly ra hai u CD mt hiu in th UCD = 40 V v ampe k ch 1A.

Nu t vo CD hiu in th 60 V th ngi ta c th ly ra hai u AB hiu in th UAB = 15 V. Coi in 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 l 2 A v UCD = 30 V.

Nu ni 2 u CD vo hiu in th 120 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 bin tr l 1,65 ( th hiu in th gia hai cc ca ngun l 3,3 V, cn khi in tr ca bin tr l 3,5 ( th hiu in th gia hai cc ca ngun 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 cng sut tiu th trn in tr R bng 16 W. Tnh gi tr ca in tr R v hiu sut ca ngun.

12. Cho mch in nh hnh v. Trong E = 48 V; r = 0; R1 = 2 (; R2 = 8 (; R3 = 6 (; R4 = 16 (. in tr ca cc dy ni khng ng k. Tnh hiu in th 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 (. Tnh hiu in th nh mc v cng sut nh mc ca bng n, bit n sng bnh thng.

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 v ca cc dy ni khng ng k. Tm cng dng in qua cc in tr, s ch ca ampe k v hiu in th gia hai cc 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 cc gi 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 vi trng hp a?

17. Mt ngun in c sut in ng 6 V, in tr trong 2 (, mc vi 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.

b) Vi gi tr no ca R th cng sut tiu th ca mch ngoi t gi tr cc i. Tnh gi tr cc i .

18. Hai ngun c sut in ng e1 = e2 = e, cc in tr trong r1 v r2 c gi tr khc nhau. Bit cng sut in ln nht m mi ngun c th 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 mch ngoi 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 in ng v in tr trong ging nhau. Nu hai pin ghp ni tip th cng dng in qua R l I1 = 0,75 A. Nu hai pin ghp song song th cng dng in qua R l I2 = 0,6 A. Tnh sut in ng v in 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 bnh thng v phi mc chng nh th no?

b) Nu ch c 6 bng n th phi mc chng th no cc bng n 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. Tnh cng dng in qua e1, e2, s ch ca ampe 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 gia 2 im A, B v cng dng in qua tng nhnh 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 = 9,5 (; R2 = 19,6 (; R3 = 4,9 (. Tnh cng dng in qua cc nhnh.

25. Cho mch in nh hnh v. Trong E1 = 6 V; E2 = 2 V; r1 = r2 = 0,4 (; n loi 6 V - 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 b ngun c 5 ngun ging nhau, mi ngun c sut in ng e = 2 V, in tr trong r = 0,2 ( mc nh hnh v. n c loi 6 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 GII1. a) q = It = 38,4 C.b) N = = 24.1019 electron.

2. a) q = = 60 C.b) I = = 0,2 A.

3. a) q = It = 28800 C; I = = 0,2 A.

b) E = = 6 V.4. Phn tch on mch: R1 nt ((R2 nt R3) // R5) nt R4.

R23 = R2 + R3 = 10 (; R235 == 5 (; R = R1 + R235 + R4 = 12 (; I = I1 = I235 = I4 = = 2 A; U235 = U23 = U5 = I235R235 = 10 V;

I5 = = 1 A; I23 = I2 = I3 = = 1 A.

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

R24 = = 4,2 (; R35 == 2,4 (; R = R1 + R24 + R35 = 9 (; U3 = U3 = U35 = I3R3 = 8 V; I35 = I24 = I1 = I = = A;

U24 = U2 = U4 = I24R24 = 14 V; U1 = I1R1 = 8 V.

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

R34 = = 2 (; R1345 = R1 + R34 + R5 = 8 (; R = = 4 (; I5 = I34 = I1 = I1345 = = 2 A; U34 = U3 = U4 = I34R34 = 4 V;

I3 = = A; I4 = = A; U1345 = U2 = UAB = I1345R1345 = 16 V;

I2 = = 2 A.

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

R35 = R3 + R5 = 30 (; R235 = = 12 (;

R4235 = R4 + R235 = 32 (; R = = 6,4 (; I3 = I5 = I35 = 2 A;

U35 = U2 = U235 = I35R35 = 60 V; I2 = = 3 A;

I235 = I4 = I4235 = = 5 A; U4235 = U1 = UAB = I4235R4235 = 160 V;

I1 = = 20 A.

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 = = 40 (;

UAC = UAB UCD = 60 V; R3 = = 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 == 0,75 A; R1 = = 20 (.

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

Ta c: R2 = = 15 (; UAC = UAB UCD = 90 V. V R3 = R4 ( I4 = = I2 + I3 = 2 + ( R3 = 30 ( = R4.

Trng hp t vo gia C v D hiu in th 120 V th on mch c (R1 nt R4) // R2) // R3. Khi UAC = UCD UAB = 100 V; I4 = I1 = = A; R1 = = 6 (.

10. Ta c: I1 = = 2 = ( 3,3 + 2r = E (1); I2 = = 1 = ( 3,5 + r = E (2). T (1) v (2) ( r = 0,2 (; E = 3,7 V.

11. Ta c: P = I2R = R ( 16 =R ( R2 - 5R + 4 = 0 ( R = 4 ( hoc R = 1 (. Khi H = = 67% hoc H = 33%.12. Ta c: R = = 6 (; I = = 6 A;

UAB = IR = 36 V; I1 = I3 = I13 = = 4,5 A;

I2 = I4 = I24 = = 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 vo im M.

13. I = = 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 + + = 5,5 (;

I = = 1 A = I1 = I24 = I35; U24 = U2 = U4 = I24R24 = I24 = 1,5 V; I2 = = 0,75 A; I4 = = 0,25 A; U35 = U3 = U5 = I35R35 = I35= 2 V; I3 = = 0,5 A; I5 == 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 = = 2 (; R123 = R1 + R23 = 3 (; R = = 2 (;I = = 2,4 A.

b) U4 = U123 = UAB = IR = 4,8 A; I123 = I1 = I23 = = 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 = = 0,8 = 80%.16. Ta c: R1 = = 12 (; R2 = = 5 (;

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

U1 = U2R2 = U12R2 = 6 V; I1 == 0,5 A; I2 = I2R2 == 0,5 A; I = I1 + I2 = 1 A; R2R2 = = 12 (; R2 = R2R2 R2 = 7 (; R12R2 = = 6 (; R = - r = 6,48 (; R1 = R - R12R2 = 0,48 (.

b) Khi R2 = 1 (: R2R2 = R2 + R2 = 6 (; R12R2 == 4 (;

R = R1 + R12R2 = 4,48 (; I = ( 1,435 A; U12R2 = U1 = U2R2 = IR12R2 = 5,74 V < 6 V nn n 1 sng yu hn; I2R2 = I2 = IR2 = = 0,96 A > = 0,5 A nn n 2 sng mnh hn.

17. a) Ta c: P = I2R = R ( 4 =R

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

b) Ta c: P = I2R = R = . V E v r khng i nn P = Pmax khi (R + ) c gi tr cc tiu, m theo bt ng thc Csi th (R + ) c gi tr cc tiu khi R = ( R = r = 2 (. Khi Pmax = = 4,5 W.

18. Cng sut cc ai m mi ngun cung cp: P1 = ; P2 = ( ; . Khi hai ngun mc ni tip cng sut cc i m b ngun cung cp: Pnt = (

( Pnt = = 48 W. Khi hai ngun mc song song, cng sut cc i m b ngun cung cp: P// = = P1 + P2 = 50 W.

19. Khi mc ni tip ta c: 0,75 = (1).

Khi mc song song ta c: 0,6 = (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 = = 12 (; I = = 0,5 A.

a) Gi N l s bng n c thp sng. Khi chng sng bnh thng 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 bng n 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 = mI ( m = = 4; 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 = = 2; n = = 3. Vy phi mc thnh hai dy, mi dy c 3 bng. Khi in tr mch ngoi: R = = 18 (. Hiu sut ca mch l: H1 = = 0,75.

Vi I2 = 3 A, ta c: m = = 6; n = = 1. Vy phi mc thnh 6 dy, mi dy c 1 bng n.

Khi in tr mch ngoi: R = = 2(.

Hiu sut ca mch l: H2 = = 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 hnh v. 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 chy trong 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 = = 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 chiu nh 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)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 hnh v. 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 in chy trong cc nhnh mch ng nh chiu ta gi s.

24. Gi s dng in chy trong cc nhnh mch c chiu nh hnh v.

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. Thay I3 vo (3), ta c UAB = - 12,15 V. V UAB < 0 nn in th im A thp hn 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 = = 12 (; R24 = R2 + R4 = 4 (; R24 == 3 (; R = R1 + R24 + R3 = 7,2 (;

a) I = = 1 A.

b) U24 = U = U24 = IR24 = 3 V; I24 = I2 = I4 = = 0,75 A; 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 = = 0,8 (; R = = 6 (;

R2 = R2 + R = 12 (; R24 == 3 (; R = R1+ R24+ R3 = 7,2 (;

a) I = = 1 A.

b) U24 = U2 = U4 = IR24 = 3 V; I2 = I2 = I = = 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 + = 0,8 (; R = = 3 (; R23 = R2 + R3 = 6 (; R23 == 2 (; R = R1 + R23 = 4,2 (;

a) I = = 2 A.

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

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 bng

A. vn k.B. ampe k.C. tnh in k.D. cng t in.3. Khi mc cc in tr ni tip 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.

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 th

A. 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 hiu in 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 s

A. 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 c in 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 hiu in 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 s

A. 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.

10. Hiu in th gia hai u mt mch in gm 2 in tr 10 ( v 30 ( ghp ni tip nhau bng 20 V. Cng dng in qua in tr 10 ( 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 V c 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 V c 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 ( v 30 ( ghp ni tip nhau bng 20 V. Hiu in th trn hai u in tr 10 ( l

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

15. Hai in tr nh nhau c ni song song c in tr tng ng bng 2 (. Nu cc in tr mc ni tip th in tr tng ng ca chng bng

A. 2 (.B. 4 (.C. 8 (.D.16 (.

16. in tr ca hai in tr 10 ( v 30 ( ghp song song l

A. 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 bng

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

19. Mt in tr R1 mc song song vi in tr R2 = 12 ( ri mc vo mt ngun in c sut in ng 24 V, in tr trong khng ng 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 bng

A. 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 bng nhau v ghp cc u ca chng li vi nhau. in tr ca on dy i 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 sut ca bng n bng

A. 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 th cng sut tiu th ca chng l 20 W. Nu cc in tr ny c mc song song v ni vo ngun U ni trn th cng sut tiu th tng cng 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 mt bng n l I = 0,273 A. Tnh s electron dch chuyn qua tit din thng 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 hay thit 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 20 pht.

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 thc hin khi mt electron dch chuyn bn trong acquy t cc dng ti cc m ca n.

A. 192.10-17 J.B. 192.10-18 J.C. 192.10-19 J. D. 192.10-20 J.

29. i vi mch in kn gm ngun in vi mch ngoi l in tr 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 dng in 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 in tr 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. A.B. A.C. 3 A.D. 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 ny l 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 trong ngun in t cc m n cc dng ca n l 18 J. Sut in ng ca 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.

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 ca lc l lm di chuyn mt in lng 8 mC gia hai cc bn trong ngun 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 v 1100 W. in tr ca bp in khi hot ng bnh thng l

A. 0,2 (.B. 20 (.C. 44 (.D. 440 (.

39. Mt bng n khi mc vo mng in c hiu in th 110 V th cng dng in qua n l 0,5 A v n sng bnh thng. Nu s dng trong mng in c hiu in th 220 V th phi mc vi n mt 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 tip vo mng in c hiu in th 240 V. cc bng n sng bnh thng th s bng n phi s dng l

A. 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 ( mc vi mch ngoi c hai in tr R1 = 20 ( v R2 = 30 ( mc song song. Cng sut ca mch ngoi l

A. 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 in ng 2 V v in tr trong 0,15 ( mc thnh 3 dy, mi dy c 6 ngun 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 khng ng k mc ni tip vi nhau v mc vi in tr 12 ( thnh mch kn. Cng dng in chy trong mch l

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

46. Mt acquy sut in ng 6 V in tr trong khng ng k mc vi bng n 6 V - 12 W thnh mch kn. Cng dng in chy qua 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 bng

A. 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 cc ca acquy vi in tr R = 9 ( th cng sut tiu th trn in tr R l

A. 3,6 W.B. 1,8 W.C. 0,36 W.D. 0,18 W

50. 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 ta ra trn vt dn trong thi gian t l

A. Q = IR2t. B. Q = . C. Q = U2Rt.D. Q = t.

52. Hai in tr ging nhau dng mc vo mt hiu in th khng i. Nu mc chng ni tip vi nhau ri mc vo hiu in th th cng sut tiu th ca chng l 20 W. Nu mc chng song song ri mc chng vo hiu in th th cng sut tiu th ca chng 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 ( mc vi mt in tr R = 2 ( thnh mch kn th cng sut tiu trn R l 16 W, gi tr ca in tr R bng

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

54. Mt mch in kn gm ngun in c in tr trong ng k vi mch 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 vi mt 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 tip th 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. Khi in tr ca bin tr l 1,65 ( th hiu in th gia hai cc ca ngun l 3,3 V, cn khi in tr ca bin tr l 3,5 V th hiu in th gia hai cc ca ngun l 3,5 V. Sut in ng v in tr trong ca ngun 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 vi mt 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 mch

A. vn bng I.B. bng 1,5I.C. bng I. D. bng 0,5I.

58. Mt b ngun c ba ngun ging nhau mc ni tip. Mch ngoi l 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 ( th c 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 v in tr trong 0,6 (. Nu em ghp chng thnh ba dy song song mi 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 (.

61. Tng chiu di ca dy dn ln hai ln v tng ng knh ca dy 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 l

A. 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 ca mt ngun in c sut in ng 6 V v in tr trong 1 ( th cng 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 l 2,2 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 ngoi bng

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 V v tip nhn cng sut 50W. c th s dng trong mng in 220 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.III. DNG IN TRONG CC MI TRNGA. TM TT L THUYT

1. Dng in trong kim loi

+ Ht ti in trong kim loi l cc electron t do. Mt ca cc electron 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 hng ca cc electron di tc dng ca in trng.

+ in tr sut ca kim loi tng theo nhit gn ng theo hm bc nht: ( = (0(1 + ((t t0)).

+ Chuyn ng nhit ca mng tinh th cn tr chuyn ng ca ht ti in lm cho in tr kim loi ph thuc vo nhit . n gn 00 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 vo nhau. Khi nhit hai mi hn T1, T2 khc nhau, trong mch c sut in 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 gi l cc cht in phn.

+ Ht ti in trong cht in phn l cc ion dng, ion m b phn li t cc phn t mui, axit, baz.

+ Cht in phn khng dn in tt bng kim loi v mt cc ion trong cht in phn nh hn mt cc electron trong kim loi, khi lng v kch thc ca cc ion ln hn khi lng v kch thc ca cc electron nn tc chuyn ng c hng ca chng nh hn.

+ Dng in trong cht in phn l dng ion dng v ion m chuyn 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 cc ion kim loi ca in cc vo trong dung dch.+ Khi lng cht thot ra cc ca bnh in phn tnh ra gam:

m = kq = It; 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, cn lng vt cht ng li in cc, gy ra hin tng in phn.

+ Hin tng in phn c p dng trong cc cng ngh luyn kim, 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 ion dng theo chiu in trng v cc ion m, cc electron ngc chiu in trng.

+ Qu trnh dn in khng t lc ca cht kh xy ra khi ta phi dng tc nhn ion ha t bn ngoi to ra ht ti in trong cht kh.

+ C bn cch chnh dng in c th to ra ht ti in mi trong cht kh:

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

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

- Catt b dng in nung nng , lm cho n c kh nng pht ra electron. 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 in vn tip tc gi c khi khng cn tc nhn ion ha tc ng t bn ngoi.

+ Tia la in l qu trnh phng in t lc hnh thnh trong cht kh 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 hp n trong xilanh.

+ H quang in l qu trnh phng in t lc hnh thnh khi dng in qua cht kh c th gi c nhit cao ca catt n pht c 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.

+ in tr sut ca cc cht bn dn c gi tr nm trong khong trung gian gia kim loi v in mi.

+ in tr sut ca cht bn dn ph thuc mnh vo nhit v tp cht.

+ 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 cc electron 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 dn in p v n trn mt tinh th bn dn. Dng in ch chy qua c lp 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 = It; m tnh ra gam th F = 96500 C/mol.

C. BI TP T LUN

1. Mt bng n 220 V - 100 W c dy tc lm bng vnfram. Khi sng bnh thng th nhit ca dy tc bng n l 20000 C. Xc nh in tr ca bng n khi thp sng v khi khng thp sng. Bit nhit ca mi trng l 200 C v h s nhit in tr ca vnfram l ( = 4,5.10-3 K-1.

2. Mt bng n 220 V - 40 W c dy tc lm bng vnfram. in tr ca dy tc bng n 200 C l R0 = 121 (. Tnh nhit ca dy tc khi bng n sng bnh thng. Cho bit h s nhit in tr ca vnfram 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. Tm h 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 bnh thng, hiu in th gia hai cc ca bng n l U2 = 240 V th cng dng in chy qua n l I2 = 8 A. Tnh nhit ca dy tc bng n khi n sng bnh thng. Bit h s nhit in tr ca dy 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 c nung 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, mi hn kia c nhng vo hi nc si. Dng milivn k o c sut nhit in ng ca cp nhit in l 4,25 mV. Tnh h s nhit in ng 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, mi nhm c 10 pin mc song song; mi pin c sut in ng 0,9 V v in tr trong 0,6 (. Mt bnh in phn ng dung dch CuSO4 c in tr 205 ( c mc vo hai cc ca b ngun ni trn. Ant ca bnh in phn bng ng. Tnh khi lng ng bm vo catt ca 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 tm kim loi l 30 cm2. Xc nh cng dng in chy qua bnh in phn. 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 dng dch CuSO4 v ant l mt thanh ng nguyn cht, ri cho dng in c cng I = 10 A chy qua trong thi gian 2 gi 40 pht 50 giy. 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 in ng 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 catt ca bnh in phn trong thi gian 1 gi 4 pht 20 giy. Bit Zn c 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 v in 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 dch AgNO3, c cc ng bng bc. in tr ca ampe k v dy ni khng ng 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 bnh in 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 in ging nhau, mi ci c sut in ng e v in tr trong r. R1 = 3 (; R2 = 6 (; bnh in phn cha dung dch CuSO4 vi cc dng bng ng v c in tr Rp = 0,5 (. Sau mt thi gian in phn 386 giy, ngi ta thy khi lng ca bn cc lm catt tng ln 0,636 gam.

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

b) Dng mt vn c in tr rt ln mc vo 2 u A v C ca b ngun. Nu b mch ngoi i th vn k ch 20 V. Tnh sut in ng v in tr trong ca mi ngun in.

14. Cho mch in nh hnh v. Bit ngun c sut in ng E = 24 V, in tr trong r = 1 (; t in c in dung C = 4 (F; n loi 6 V - 6 W; cc in tr c gi tr R1 = 6 ; R2 = 4 ; bnh in phn ng dung dch CuSO4 v c ant lm bng Cu, c in tr Rp = 2. B qua in tr ca dy ni. Tnh:

a) in tr tng ng ca mch ngoi.

b) Khi lng Cu bm vo catt sau 16 pht 5 giy.

c) in tch ca t in.

15. Cho mch in nh hnh v:

B ngun gm 6 ngun ging nhau, mi ngun c sut in ng e = 2,25 V, in tr trong r = 0,5 (. Bnh in phn c in tr Rp cha dung dch CuSO4, ant lm bng ng. T in c in dung C = 6 (F. n loaij4 V - 2 W, cc in tr c gi tr R1 = R2 = R3 = 1 (. Ampe k c in tr khng ng k, b qua in tr ca dy ni. Bit n sng bnh thng. Tnh:

a) Sut in ng v in tr trong ca b ngun.

b) Hiu in th UAB v s ch ca ampe k.

c) Khi lng ng bm vo catt sau 32 pht 10 giy v in tr Rp ca bnh in phn.

d) in tch v nng lng ca t in.

16. Cho mch in nh hnh v. Trong b ngun gm 8 ngun ging nhau, mi ci c sut in ng e = 5 V; c in tr trong r = 0,25 ( mc ni tip; n c loi 4 V - 8 W; R1 = 3 (; R2 = R3 = 2 ( ; RB = 4 ( v l bnh in phn ng dung dch Al2(SO4)3 c cc dng bng Al. iu chnh bin tr Rt n sng bnh thng. Tnh:

a) in tr ca bin tr tham gia trong mch.

b) Lng Al gii phng cc m ca bnh in phn trong thi gian 1 gi 4 pht 20 giy. Bit Al c n = 3 v c A = 27.

c) Hiu in th gia hai im A v M.

17. Cho mch in nh hnh v. Trong E1 = 6 V; E2 = 2 V ; r1 = r2 = 0,4 (; n loi 6 V - 3 W; R1 = 0,2 (; R2 = 3 (; R3 = 4 (; RB = 1 ( v l bnh in phn ng dung dch AgNO3, c cc dng bng Ag. Tnh:

a) Cng dng in chy trong mch chnh.

b) Lng Ag gii phng cc m ca bnh in phn trong thi gian 2 gi 8 pht 40 giy. Bit Ag c n = 1 v c A = 108.

c) Hiu in th gia hai im M v N.

18. Cho mch in nh hnh v. Trong b ngun c 8 ngun ging nhau, mi ngun c sut in ng e = 1,5 V, in tr trong r = 0,5 (, mc thnh 2 nhnh, mi nhnh c 4 ngun mc ni tip. n loi 3 V - 3 W; R1 = R2 = 3 (; R3 = 2 (; RB = 1 ( v l bnh in phn ng dung dch CuSO4, c cc dng bng Cu. Tnh:

a) Cng dng in chy trong mch chnh.

b) Tnh lng Cu gii phng ra cc m trong thi gian 32 pht 10 giy. Bit Cu c nguyn t lng 64 v c ho tr 2.

c) Hiu in th gia hai im M v N.

19. Mt bnh in phn c ant l Ag nhng trong dung dch AgNO3, mt bnh in phn khc c ant l Cu nhng trong dung dch CuSO4. Hai bnh mc ni tip nhau vo mt mch in. sau 2 gi, khi lng ca c hai catt tng ln 4,2 g. Tnh cng dng in i qua hai bnh in phn v khi lng Ag v Cu bm vo catt mi bnh.

20. Mt it in t c dng in bo ha Ibh = 5 mA khi hiu in th gia ant v catt l U = 10 V.

a) Tnh s electron p vo ant trong mt giy.

b) Tnh ng nng ca electron khi n ant, bit electron ri catt khng vn tc ban u.

HNG DN GII

1. Khi thp sng in tr ca bng n l: R = = 484 (. Khi khng thp sng in tr ca bng n l: R0 = = 48,8 (.

2. Khi sng bnh thng: R = = 1210 (.

V: R = R0(1+((t t0)) ( t = - + t0 = 20200 C.

3. Khi sng bnh thng: R = = 242 (.

nhit 1000 C: R0 = = 22,4 (.

V R = R0(1+((t t0)) ( ( = - = 0,0041 K-1.

4. in tr ca dy tc 250 C: R1 = = 2,5 (. in tr ca dy tc khi sng bnh thng: R2 = = 30 (.

V: R2 = R1(1+((t2 t1)) ( t2 = - + t1 = 26440 C.

5. Ta c: E = (T(T2 T1) = 0,0195 V.6. Ta c: E = (T(T2 T1) ( (T = = 42,5.10-6 V/K.7. Ta c: E = (T(T2 T1) ( T2 = + T1 = 14880 K = 12150 C.

8. Ta c: Eb = 3e = 2,7 V; rb = 3= 0,18 (; I = = 0,01316 A;

m = It = 0,013 g.9. Ta c m = (V = (Sh = 1,335 g; m = It ( I = = 2,47 A.

10. Ta c: m = It = (Sh ( h = = 0,018 cm.

11. Gi x l s nhnh th mi nhnh s c y = ngun. Khi :

Eb = ye = .1,5 = ; rb = = ; I = = . I = Imax th 3,6x = ( x = 3. Vy phi mc thnh 3 nhnh, mi nhnh c 12 ngun mc ni tip. Khi Imax = 2,5 A; m = It = 3,25 g.12. a) Ta c: R = = 3 (; R2 = R2 + R = 12 (; U2 = U3p = UCB = IA2.R2 = 4,8 V; I3p = I3 = Ip = IA1 IA2 = 0,2 A; R3p = = 24 (; Rp = R3p R3 = 22 (.

b) in tr mch ngoi: R = R1 + RCB = R1 + = 28 (;

I = ( 16,8 + 0,3n = 1,5n ( n = 14 ngun;

Cng sut ca b ngun: Png = Ieb = Ine = 12,6 W.

c) S ch vn k: UV = U = IR = 16,8 V.

d) Khi lng bc gii phng: m = Ipt = 0,432 g.

e) I = IA2 = 0,4 A < Im = = 1 A nn n sng yu hn bnh thng.13. a) Ta c: m = It ( I = = 5 A; R12 = = 2 (;

U12 = U1 = U2 = IR12 = 10 V; I1 = = A; I2 = = A.

b) Khi b mch ngoi th UV = Eb = 2e ( e = = 10 V; R = R12 + Rp = 2,5 (; I = ( 12,5 + 7,5r = 20 ( r = 1 (.

14. a) Ta c: R = = 6 (; R1 = R1 + R = 12 (;

R12 = = 3 (; R = Rp + R12 = 5 (.

b) I = Ip = = 4 A; m = Ipt = 12,8 g.

c) U12 = U1 = U2 = IR12 = 12 V; I1 = I1 = I = = 1 A;

UC = UAM = UAN + UNM = IRp + I1R1 = 14 V; q = CUC = 56.10-6 C.15.a) Ta c: Eb = e + 2e + e = 4e = 9 V; rb = r + + r = 3r = 1,5 (.

b) Ta c: R = = 8 (; R1 = R1 + R = 9 (. V n sng bnh thng nn: I1 = I1 = I = Im = = 0,5 A; UAB = U1 = Up2 = I1 R1 = 4,5 V; I =

( 4,5RAB + 11,25 = 9RAB ( RAB = 2,5 (.

S ch ampe k: IA = I = = 1,8 A.

c) Ta c: Ip2 = Ip = I2 = I I1 = 1,3 A; m = Ipt = 0,832 g;

Rp2 = = 3,46 (; Rp = Rp2 R2 = 2,96 (.

d) Ta c: UC = UMN = VM VN = VM VB + VB VN = UMB UNB = IR - I2R2 = 3,35 V;

q = CUC = 20,1.10-6C; W =CU2 = 33,67.10-6 J.16. a) Ta c: R = = 2 (; R3 = R3 + R = 4 (; R2B = R2 + RB = 6 (; RCD = = 2,4 (. V n sng bnh thng nn: I3 = I3 = I = Im = = 2 A; U3 = U2B = UCD = I3R3 = 8 V; I = = A; Eb = 8e = 40 V; rb = 8r = 2 (; I = ( = ( 10R + 20 = 120 ( R = 10 (; Rt = R R1 RCD = 4,5 (.

b) Ta c: UCD = U2B = U3 = IRCD = 8 V;

I2B = I2 = IB = = A; m = IBt = 0,48 g.

c) UAM = VA VM = VA VC + VC VM = UAC + UCM = IR1 + I2R2 = 12,67 V.

17. a) Eb = E1 + E2 = 8 V; rb = r1 + r2 = 0,8 (; R = = 12 (;

R2B = R2 + RB = 4 (; RCD = = 3 (;

R = R1 + RCD + R3 = 7,2 (; I = = 1 A.

b) UCD = U = U2B = IRCD = 3 V; I2B = I2 = IB = = 0,75 A;

m = IBt = 6,48 g.

c) UMN = VM VN = VM VC + VC VN = UMC + UCN = I(R1 + r1) E1 + I2R2 = - 3,15 V; du - cho bit in th im M thp hn in th im N.

18. a) Eb = 4e = 6 V; rb = = 1 (; R = = 3 (; R2 = R + R2 = 6 (; RB3 = RB + R3 = 3 (; RCB = = 2 (;R = R1 + RCB = 4 (; I = = 1,2 A.

b) UCB = U2 = UB3 = IRCB = 2,4 V; IB3 = IB = I3 = = 0,8 A;

m = IBt = 0,512 g.

c) I2 = I = I2 = = 0,4 A; UMN = VM VN = VM VC + VC VN = - UCM + UCN = - IR + IBRB = - 0,4 V; du - cho bit in th im M thp hn in th im N.

19. m1 = ; m2 = ; m1 + m2 = (+ )

( I = = 0,4 A; m1 = = 3,24 g; m2 = m m1 = 0,96 g.

20. a) n = = 3,125.1016 electron/s.

b) W = eU = 1,6.10-18 J.

D. TRC NGHIM KHCH QUAN1. Ht mang ti in trong kim loi l

A. ion dng v ion m.B. electron v ion dng.

C. electron.

D. electron, ion dng v ion m.

2. Ht mang ti in trong cht in phn l

A. ion dng v ion m.B. electron v ion dng.

C. electron.

D. electron, ion dng v ion m.

3. Cho dng in c cng 0,75 A chy qua bnh in phn ng dung dch CuSO4 c cc dng bng ng trong thi gian 16 pht 5 giy. Khi lng ng gii phng ra cc m l

A. 0,24 kg.B. 24 g.C. 0,24 g.D. 24 kg.

4. Khi nhit tng in tr ca kim loi tng l do

A. s electron t do trong kim loi tng.

B. s ion dng v ion m trong kim loi tng.

C. cc ion dng v cc electron chuyn ng hn n hn.

D. si dy kim loi n di ra.

5. Khi nhit tng in tr ca cht in phn gim l do

A. s electron t do trong bnh in phn tng.

B. s ion dng v ion m trong bnh in phn tng.

C. cc ion v cc electron chuyn ng hn n hn.

D. bnh in phn nng ln nn n rng ra.

6. Pht biu no di y khng ng? Bn dn tinh khit khc bn dn pha ln tp cht ch

A. bn dn tinh khit c mt electron v l trng gn nh nhau.

B. cng mt nhit , mt ht mang in t do trong bn dn tinh khit t hn trong bn dn c pha tp cht.

C. in tr ca bn dn tinh khit tng khi nhit tng.

D. khi thay di nhit in tr ca bn dn tinh khit thay i nhanh hn in tr ca bn dn c pha tp cht.

7. Dng chuyn di c hng ca cc ion dng, ion m v electron l dng in trong mi trng

A. kim loi. B. cht in phn. C. cht kh. D. cht bn dn.

8. c c bn dn loi n ta phi pha vo bn dn tinh khit silic mt t tp cht l cc nguyn t

A. thuc nhm II trong bng h thng tun hon.

B. thuc nhm III trong bng h thng tun hon.

C. thuc nhm IV trong bng h thng tun hon.

D. thuc nhm V trong bng h thng tun hon.

9. Hin tng to ra ht ti in trong dung dch in phn

A. l kt qu ca dng in chy qua cht in phn.

B. l nguyn nhn chuyn ng ca cc phn t.

C. l dng in trong cht in phn.

D. cho php dng in chy qua cht in phn.

10. Cho dng in c cng 2 A chy qua bnh in phn ng dung dch mui ng c cc dng bng ng trong 1 gi 4 pht 20 giy. Khi lng ng bm vo cc m l

A. 2,65 g.B. 6,25 g.C. 2,56 g.D. 5,62 g.

11. Nguyn nhn lm xut hin cc ht ti in trong cht in phn l

A. do s chnh lch nhit gia hai in cc.

B. do s phn li ca cc cht tan trong dung mi.

C. do s trao i electron vi cc in cc.

D. do nhit ca bnh in phn gim khi c dng in chy qua.

12. Bng n ca tivi hot ng in p (hiu in th) 30 kV. Gi thit rng electron ri khi catt vi vn tc ban u bng khng. ng nng ca electron khi chm vo mn hnh l

A. 4,8.10-16 J.B. 4,8.10-15 J.C. 8,4.10-16 J.D. 8,4.10-15 J.13. Trong it bn dn, ngi ta s dng

A. hai loi bn dn tinh khit c bn cht khc nhau.

B. mt bn dn tinh khit v mt bn dn c pha tp cht.

C. hai loi bn dn c pha tp cht c bn cht khc nhau.

D. hai loi bn dn c pha tp cht c bn cht ging nhau.

14. Khi nhit tng th in tr ca cht in phn

A. tng. B. gim.

C. khng i. D. c khi tng c khi gim.

15. Nguyn nhn lm xut hin cc ht ti in trong cht kh iu kin thng l

A. cc electron bt khi cc phn t kh.

B. s ion ha do va chm.

C. s ion ho do cc tc nhn a vo trong cht kh.

D. khng cn nguyn nhn no c v c sn ri.

16. Chn cu sai trong cc cu sau

A. Trong bn dn tinh khit cc ht ti in c bn l cc electron v cc l trng.

B. Trong bn dn loi p ht ti in c bn l l trng.

C. Trong bn dn loi n ht ti in c bn l electron.

D. Trong bn dn loi p ht ti in c bn l electron.

17. iu no sau y l sai khi ni v lp chuyn tip p-n?

Lp chuyn tip p-n

A. c in tr ln v gn c rt t cc hi ti in t do.

B. dn in tt theo chiu t p sang n.

C. dn in tt theo chiu t n sang p.

D. c tnh cht chnh lu.

18. Dng in trong kim loi l dng chuyn ng c hng ca

A. cc ion dng cng chiu in trng.

B. cc ion m ngc chiu in trng.

C. cc electron t do ngc chiu in trng.

D. cc prtn cng chiu in trng.

19. Nguyn nhn gy ra in tr ca vt dn lm bng kim loi l

A. do cc electron va chm vi cc ion dng nt mng.

B. do cc electron dch chuyn qu chm.

C. do cc ion dng va chm vi nhau.

D. do cc nguyn t kim loi va chm mnh vi nhau.

20. Trong dung dch in phn, cc ht ti in c to thnh do

A. cc electron bt ra khi nguyn t trung ha.

B. s phn li cc phn t thnh ion.

C. cc nguyn t nhn thm electron.

D. s ti hp cc ion thnh phn t.

21. Khi nhit tng th in tr ca cht bn dn tinh khit

A. tng.

B. gim.

C. khng i. D. c khi tng c khi gim.

22. Hin tng siu dn l hin tng m khi ta h nhit xung di nhit TC no th in tr ca kim loi (hay hp kim)

A. tng n v cc.

B. gim n mt gi tr khc khng.

C. gim t ngt n gi tr bng khng.

D. khng thay i.

23. Khi vt dn trng thi siu dn, in tr ca n

A. v cng ln.

B. c gi tr m.

C. bng khng.

D. c gi tr dng xc nh.

24. Chn cu sai

A. iu kin bnh thng, khng kh l in mi.

B. Khi b t nng cht kh tr nn dn in.

C. Nh tc nhn ion ha, trong cht kh xut hin cc ht ti in.

D. Khi nhit h n di 0 0C cc cht kh dn in tt.

25. c th to ra s phng tia la in gia hai in cc t trong khng kh iu kin thng th

A. hiu