# Electric field is zero inside a conductor?

#### Ebn_Alnafees

what is the physical explanation of the fact that the electric field is zero inside a conductor???

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#### Crosson

what is the physical explanation of the fact that the electric field is zero inside a conductor???
This is not true in general, but it is true in the realm of electrostatics. That is, if we charge a conductor, and allow it to reach equilibrium, then the electrci field is zero inside.

This is because, in equilibrium, no charges can be moving. The only way for this to be is if the (macroscopically averaged, dont think of particles think of fluid) electric field is zero.

#### James Jackson

Or... Are you thinking Faraday's cage kind of thing?

#### Knavish

.. I think Crosson's explanation dealt with Faraday's cage.

?

#### Dr.Brain

The more simple explaination is using the Gauss Law.When a conductor is charged , after equilibrium is reached , charges rest on the surface of the conductor , and inside a cavity , that is open space no charge resides , by Gauss Law , no electric field exists inside it and hence these cavity is kept protected from outside electrical influences , phenomena called "electrostatic shielding'.

BJ

#### Ebn_Alnafees

thank you all i think i got it

#### Antiphon

The electric feild is determined by the way in which the voltage changes from
place to place. If you are inside a metal sphere, the voltage is the same
everywhere. Since the voltage isn't changing as you move around, the electric
field measures as zero everywhere inside the sphere.

#### James R

Homework Helper
Gold Member
As somebody else said, the electric field is only zero in an electrostatic situation, in which it is assumed that all the charges have had time to "settle down" before we look at the field. We also assume there are no currents flowing (obviously, a wire carrying current has an electric field inside, or else electrons wouldn't move along it).

If there was a field inside a conductor in electrostatic equilibrium, then the free charges in the conductor would accelerate in the direction of the field - which would mean the conductor wasn't in equilibrium - a contradiction. Hence, the conclusion follows.

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