8. a) A spherical conducting shell of outer radius 10 cm, has a charge of -14µC

ID: 2307331 • Letter: 8

Question

8. a) A spherical conducting shell of outer radius 10 cm, has a charge of -14µC on its outer surface

and has a charges particle in its hollow. If the net charge on the shell is -10µC,

(a) what is the charge on the inner surface of the shell which has radius of 8 cm? And (b) what is the charge on

the particle?

b) For problem # 8 write an expression for the electric field at

(a) r <8cm;

(b) 8cm <r<10cm

c) For problem #8 plot the electric FLUX (y-axis) vs distance from the particle (x-axis).

field inside conductor is alway zero.

a) and from guass law,

E . A = Qinside / e0 = 0

Qinside = 0

total charge upto inner surface = 0

if chare point is +ve charged then it will come to outer surface.

that is not possible because charge on outer surface is more negtaive than total charge.

if charge is negative that means it will go to inner surface.

hence inner surface charge + particle charge = 0

inner surface + outer surface = - 10uC

inner surface - 14uC = -10uC

inner surface = 4uC

b) inner surface charge + particle charge = 0

4uC + particle charge = 0

perticle charge = - 4uC

a) r < 8cm

Qinside = 0

E = 0

b) 8 < r < 10cm

Qin = 0

E = 0

c) r > 10cm

Qin = -10 - 4 = -14 uC

E A = Qin / e0

E (4 pi r^2 ) = (14 x 10^-6 ) / (8.854 x 10^-12)

E = 125828.39 / r^2

towards the centre of sphere

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