# Charge placed in a cavity in a conductor

1. Oct 24, 2015

### Ajay.makhecha

If a conductor has a cavity in it and if a charge is placed in the cavity, then will the electric feild inside it be zer

2. Oct 24, 2015

### Staff: Mentor

Welcome to the PF.

The field inside the cavity will not be zero. Is there a reason that you think it would be zero?

3. Oct 24, 2015

### Ajay.makhecha

Actually I just started learning electrostatics. In our texts it is mentioned that electric feild inside a conductor must be 0. But nothing is mentioned if it has a charge inside it. So I just asked out of curiosity. Btw can you say why it wont be zero?

4. Oct 24, 2015

### Staff: Mentor

(I fixed "u" to "you" in your post -- we don't use text speak at the PF )

There is a field because there is a charge (source of E-field) with no conductor shielding it from the space inside the cavity.

5. Oct 24, 2015

### my2cts

"Inside a conductor" in this case should be read as inside the volume actually occupied by the conductor.
It can also mean a hollow space surrounded by a conductor, in which the field is not necessarily zero.
Suppose a charge q is in the hollow space
On the inner and outer surfaces charges (-q and +q) are distributed such that the electric field inside the metal is cancelled.
Outside the metal a field exists due to the outer surface charge distribution of +q. If the conductor and the cavity are spherical and concentric,
this field will be equal to the field of a free charge.