# PHYS 2212 Module 2.4

## Conductors in Electrostatic Equilibrium

2.4 Conductors in Electrostatic Equilibrium

### Learning Objectives

By the end of this section, you will be able to:

• Describe the electric field within a conductor at equilibrium
• Describe the electric field immediately outside the surface of a charged conductor at equilibrium
• Explain why if the field is not as described in the first two objectives, the conductor is not at equilibrium

### Gauss’s Law and Conductors

Practice!

Discuss!

Reflect on these questions and take notes on how you would answer them. Then we will share these thoughts together in a class discussion.

A charge −2Q is brought near a conducting sphere.

What is the electric field in the region r < Ra (inside the cavity of the conducting sphere)?

A ball with charge −50e lies at the center of a hollow spherical metal shell that has a net charge of −100e.

What are the charges on the shell’s inner surface and outer surface, respectively?

A ball with charge −50e lies off-center inside a hollow spherical metal shell that has a net charge of −100e.

What are the charges on the shell’s inner surface and outer surface, respectively?

A positive charge +Q is kept fixed at the center of a spherical neutral conducting shell. An object with negative charge −Q is brought near the outside of the sphere.

Which picture best represents the charge distributions?