Electric fields

Question 1

2 spheres touched. Then q’1 = ?

Answer 1

r1 *(q1+q2)/(r1+r2)

Question 2

induced charge q = ?

Answer 2

Q(1- 1/K)

Question 3

Electric field due to rod at a point P which makes angle alpha and beta with ends of rod

Answer 3

Ex = lambda/4piepsr * (sin alpha + sin beta)
Ey = lambda/4piepsr * (cosalpha - cosbeta)

Question 4

Electric field at the centre of an arc subtending angle theta at centre

Answer 4

lambda/2piepsr * sin(theta/2)

Question 5

field due to disc

Answer 5

sigma/2eps * (1 - x/(x^2 + R^2)^3/2)

Question 6

field due to ring

Answer 6

qx/4pieps(x^2+R^2)^3/2

Question 7

Field due to hemispherical shell at the centre

Answer 7

sigma/4eps

Question 8

E due to wire

Answer 8

lambda/2piepsr

Question 9

E due to sheet

Answer 9

sigma/2eps

Question 10

field due to dipole at r,theta

Answer 10

kp/r^3 * root(1+3cos^2theta)

Question 11

Force on dipole in non uniform field

Answer 11

F = dU/dr = p dE/dr

Question 12

Ecavity of sphere?

Answer 12

rho/3eps OPvector

OP is distance from centre of sphere to centre of cavity)

Question 13

charge density and r relation

Answer 13

inversely

Question 14

Potential due to dipole

Answer 14

kpcostheta/r^2

Question 15

Potential due to ring

Answer 15

kq/root(x^2 + R^2)