AP Physics C E and M

Question

A 5 cm radius conducting sphere has a charge density of 2.0x10^-6 C/m² on its surface. Find the electric potential of the sphere.

7.2x10⁶ V

1.1x10⁴ V

3.6x10⁵ V

2.3x10⁵ V

2.2x10⁴ V

Do I want to use the formula of V= K(q/r), or do I need a different one because over here we are given charge density and not charge?

Answer 1

First find the total charge by multiplying the charge density by the area of the sphere,

Q = 2 x 10^-6 x 4 x pi x 0.05^2 = 6.28 x 10^-8 C.

Now you can use the formula V = k x 6.28 x 10^-8 / 0.05 = 1.1 x 10^4V. Use mks units.