# Homework Help: +2uC and -2uC charges inside a closed gauss box.

1. Mar 5, 2012

### killerdevil

Electric Field inside a closed gauss box.

1. The problem statement, all variables and given/known data

there are +2uC and -2uC charges inside a close "Gauss" box. Which of the following statement is true?

2. Relevant equations

given option are:
1) the net electric flux through the box is zero
2) the electric field is zero everywhere outside the box
3) the electric field is zero everywhere inside the box
4) the electric field is zero everywhere on the surface of the box
5) the charge inside the box must be equal to the charge outside the box, but with the different sign

3. The attempt at a solution

filtering out the above options, i am stuck with just this 2 choice:
1) the net electric flux through the box is zero; &
3) the electric field is zero everywhere inside the box.

if i assume that the conductor is in electrostatic equilibrium, the obvious answer would be (3). then again, since it is a enclosed box, am i right to say that the net electric flux through the box is zero?

sorry. i am confused.

Last edited: Mar 5, 2012
2. Mar 5, 2012

### rude man

You have to assume the charges are separated, i.e. the inside of your box is a dielectric (insulator), otherwise the charges would null each other out. So your statement that the box is a conductor is impossible.

So think instead of these charges dispersed in any way you can think. For example, you might have the + charges nearer one end of the box, the - ones near the other.