xacdinhcamungtu

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PHNG PHP GI

CM NG T TNG HP DO HAI DNG

A Phng php:

Bi ton 1: Xc nh cm ng t

Bc 1: V hnh

*Xc nh v tr tng i c

*Dng quy tc nm bn tay ph

2B

do hai dng in gy ra

Ch :

Khi v hnh nn I vung gc v

M

B

mp(M, I)

Bc 2: p dng cng thc B = 2.10

Bc 3: S dng nguyn l ch

Suy ra: B = 2 21 2 1 2

B + B + 2B B cos

Thay B1, B2 tnh c b

Bi ton 2: Tm qu tch cc i

N 1 2B = B + B

(1) N phi thuc mt phng ch

*Nu I1, I2 cng chiu th N n

*Nu I1, I2 ngc chiu th N n

(2) 1 2

1 2

I I =

r r

D

Luy

Gia s t

/c: S

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PHP GII DNG BI TP XC

P DO HAI DNG IN THNG SONG SONG GY RA

ng t tng hp do hai dng in thng, song song gy ra

a im M vi hai dng in.

m bn tay phi xc nh phng chiu ca cc vc t c

I vung gc vi mt phng hnh v bng cch dng k hi

c B = 2.10-7I

r tnh B1, B2.

ng cht t trng 1 2

B = B + B

1 2 1 2B + B + 2B B cos vi =

1 2

(B , B )

(*)

bc 2, xc nh t hnh v v gi thi

m c cm ng t bng khng

1 2N 1 2

1 2

B B (1)B = B + B

B = B (2)

ng cha I1, I2

u th N nm gia I1 v I2

u th N nm ngoi I1, I2 (gn dng in c c

Trung tm Thy Hong

Dy nhm cht lng cao ton l ha ting anh l

Luyn thi vo lp 10, luyn thi quc gia THPT

Gia s ti nh cc mn vn ha cho hc sinh c

/c: S 8A ngch 69B ng 121 Kim Ngu HBT

0974 222 456

NH

NG SONG SONG GY RA

ng, song song gy ra

a cc vc t cm ng t 1

B

,

ng cch dng k hiu hoc

thit vo (*) B = ?

n c cng ln hn)

C Nh

ng anh lp 10, 11, 12

c gia THPT

p 2, cp 3

HBT HN

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Kt vi 1 phng trnh lin h gia r1, r2 vi khong cch hai dng in r1, r2

Kt lun: Qu tch cc im c B = 0 l ng thng song song vi 2 dng in, cch I1

khong r1 v cch I2 khong r2.

B Bi tp vn dng

Bi 1. Hai dy dn thng, rt di, t song song, cch nhau 20 cm trong khng kh, c hai

dng in ngc chiu, c cng I1 = 12 A; I2 = 15 A chy qua. Xc nh cm ng t

tng hp do hai dng in ny gy ra ti im M cch dy dn mang dng I1 15 cm v cch

dy dn mang dng I2 5 cm.

Bi 2. Hai dy dn thng, rt di, t song song, cch nhau 10 cm trong khng kh, c hai

dng in ngc chiu, c cng I1 = 6 A; I2 = 12 A chy qua. Xc nh cm ng t tng

hp do hai dng in ny gy ra ti im M cch dy dn mang dng I1 5 cm v cch dy

dn mang dng I2 15 cm.

Bi 3. Hai dy dn thng, rt di, t song song, cch nhau 10 cm trong khng kh, c hai

dng in cng chiu, c cng I1 = 9 A; I2 = 16 A chy qua. Xc nh cm ng t tng

hp do hai dng in ny gy ra ti im M cch dy dn mang dng I1 6 cm v cch dy

dn mang dng I2 8 cm.

Bi 4. Hai dy dn thng, rt di, t song song, cch nhau 20 cm trong khng kh, c hai

dng in ngc chiu, c cng I1 = I2 = 12 A chy qua. Xc nh cm ng t tng hp

do hai dng in ny gy ra ti im M cch dy dn mang dng I1 16 cm v cch dy dn

mang dng I2 12 cm.

Bi 5. Hai dy dn thng, rt di, t song song, cch nhau 20 cm trong khng kh, c hai

dng in ngc chiu, cng cng I1 = I2 = 9 A chy qua. Xc nh cm ng t tng hp

do hai dng in ny gy ra ti im M cch u hai dy dn mt khong 30 cm.

Bi 6. Hai dy dn thng, rt di, t song song, cch nhau 10 cm trong khng kh, c hai

dng in cng chiu, cng cng I1 = I2 = 6 A chy qua. Xc nh cm ng t tng hp

do hai dng in ny gy ra ti im M cch u hai dy dn mt khong 20 cm.

Bi 7. Hai dy dn thng rt di, t song song trong khng kh cch nhau mt on d = 12

cm c cc dng in cng chiu I1 = I2 = I = 10 A chy qua. Mt im M cch u hai dy

dn mt on x.

a) Bit x = 10 cm. Tnh ln cm ng t tng hp do hai dng in chy trong hai dy dn gy ra ti im M.

b) Hy xc nh x ln cm ng t tng hp do hai dng in gy ra t gi tr cc i. Tnh gi tr cc i .

Bi 8. Hai dy dn thng di v hn, t song song trong khng kh cch nhau mt on d =

2a c cc dng in ngc chiu cng cng I1 = I2 = I chy qua.

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a) Xc nh cm ng t tng hp do hai dng in ny gy ra ti im M cch u hai dy dn mt on x.

b) Hy xc nh x ln cm ng t tng hp do hai dng in gy ra t gi tr cc i. Tnh gi tr cc i .

Bi 9. Hai dy dn thng, rt di, t song song, cch nhau 15 cm trong khng kh, c hai

dng in cng chiu, c cng I1 = 10 A, I2 = 5 A chy qua. Tm qu tch im M m ti

cm ng t tng hp do hai dng in ny gy ra bng 0.

Bi 10. Hai dy dn thng, rt di, t song song, cch nhau 10 cm trong khng kh, c hai

dng in ngc chiu, c cng I1 = 20A, I2 = 10A chy qua. Tm qu tch im N m

ti cm ng t tng hp do hai dng in ny gy ra bng 0.