Problem 21.

Three small spheres are enclosed in surface carrying charges q1 = 4 nC, q2 = -10.00 nC, and q3 = 5 nC.

 Surface (s)                        What it encloses

s1                                        q1

s2                                        q2

s3                                        q1 and q2

s4                                        q1 and q3

s5                                        q1, q2 and q3

Find the net electric flux through each of the following closed surfaces.

(a) s1

(b) s2    

(c) s3        

(d) s4

(e) s5

Solution

From Gauss's law the flux through any surface depends only on the charge inside of the surface

Then

(a)

where

(b)

(c)

(d)

(e)