Why is the electric field inside a conductor zero?

Timebomb3750

1. Homework Statement
Why is the electric field, in static equilibrium, equal to zero.

3. The Attempt at a Solution

The only way I can see why is to picture that there was an electric field inside a conductor. The field would cause the electrons to move freely inside the conductor. This movement of electrons would cancel out the electric field.

That's my two cents. I'm sure I could expand on this more, but I'm confused because I'm having a really hard time trying to picture this in my head.

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HallsofIvy

Homework Helper
You can also show this the same way you show that the gravitational force inside a sphere is 0. Given a point, P, inside the sphere, take a small section of surface area on the surface of the sphere and draw a line from every point in that section through P to the other side of the sphere. Note that the area will be directly proportional to the square of the distance from P and since the force is inversely proportional to the square of the distance, the force from the two sections cancel.

SammyS

Staff Emeritus
Homework Helper
Gold Member
1. Homework Statement
Why is the electric field, in static equilibrium, equal to zero.

3. The Attempt at a Solution

The only way I can see why is to picture that there was an electric field inside a conductor. The field would cause the electrons to move freely inside the conductor. This movement of electrons would cancel out the electric field.

That's my two cents. I'm sure I could expand on this more, but I'm confused because I'm having a really hard time trying to picture this in my head.
Yes, that's the basic idea.

In a conductor charge is (relatively) free to move. If there were an electric field within a conductor, charges would move. They would move in such a way and to such locations so as to cancel that field.

As a result, any excess local charge can only reside on the surface of a conductor under conditions of equilibrium.

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