# Why Electric Fields are perpendicular

1. Jul 8, 2009

### KatieD

1. The problem statement, all variables and given/known data
If electric fields are perpendicular to the equipotential surface, what is the orientation of the field on the surface of a conductor (like metal)? Why is this so?

2. Relevant equations

E= ∆V/d

3. The attempt at a solution

I know that there is no charge within a conductor and it moves to the edges. I am confused with how this affects the electric field lines. I also know that electric field lines point out if a charge is positive and in if a charge is negative.

I am just confused with electric fields when there is a conductor.

Thanks :)
Katie

2. Jul 8, 2009

### Staff: Mentor

If you use a DVM to measure the voltage difference between two points on a conductive surface, what voltage do you think you will measure (assuming little or no current is flowing in the conductor)? Does that help?

3. Jul 8, 2009

### KatieD

You wont measure any voltage, does this mean that the electrical field would be zero?

4. Jul 8, 2009

### Staff: Mentor

Something like that. It means that the two points on the conductive surface have no "potential" difference between them. So in other words, you could call the surface of a conductor an __________ surface, right? And since the E field is always perpendicular to that kind of surface, what can you say?

5. Jul 8, 2009

### KatieD

Oh an equipotential surface! so the electric field would be perpendicular to the surface!

6. Jul 8, 2009

### KatieD

(sorry it took me so long I had to leave for physical therapy)

7. Jul 8, 2009

Bingo!