# Homework Help: Electric field at the surface of a conductor

1. Dec 27, 2007

### jakeham

1. The problem statement, all variables and given/known data
Put in plain words: "In a static situation, the electric field at the surface of a conductor can have no component parallel to the surface, because this would violate the condition that the charges on the surface are at rest."
Would this same statement be a valid one for tha electric field at the surface of an insulator?

2. Relevant equations

3. The attempt at a solution
I can't understand the sentence, and can't figure out if it's valid for an insulator.

2. Dec 27, 2007

### Dick

The charges in a conductor are mobile. If there is a parallel component of the electric field at the surface then it will cause the surface charges to move (hence not 'static'). The charges in an insulator are not mobile. So the argument doesn't hold.

3. Dec 27, 2007

### chaoseverlasting

In a STATIC situation, the charges ARE at rest. The statement holds

4. Dec 27, 2007

### Dick

The 'statement' is that there is no E field component parallel to the surface of the body. In the insulating case the charges won't move even if there is an E field. Hence there CAN be a E field in the static case. Hence the statement does NOT hold.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook