Find the value of the potential

Question

A total electric charge of 5.00  is distributed uniformly over the surface of a metal sphere with a radius of 30.0cm . The potential is zero at a point at infinity.

Find the value of the potential at 60.0cm from the center of the sphere. 

Express your answer in volts

Find the value of the potential at 30.0 cm from the center of the sphere.

Express your answer in volts.

Find the value of the potential at 13.0 cm from the center of the sphere.

Express your answer in volts.

Answer 1

The general formula for the electric potential, V(r) is

V(r) = k Q/ r for r > .3 m and V(r) = k Q / (.3) for r < .3 m

Here k = 9 x 10^9 and Q = 5 (C)

So it is easy to plug in.