# Force between 2 parallel plates!

1. Dec 10, 2011

### khfrekek1992

1. The problem statement, all variables and given/known data
Two parallel sheets of conducting metal are very close to each other (A>>d), they have charges of Q1 and Q2 on them. What is the force between these two plates?

2. Relevant equations
Gauss' Law

3. The attempt at a solution
From what I understand, you can use Gauss' law to calculate the field between the plates, but I don't know how to go about doing this. Any suggestions?

2. Dec 10, 2011

### Delphi51

3. Dec 11, 2011

### I like Serena

Start with one plate and use Gauss to calculate the electric field (like in Delphi's first link).
Then add the second plate and use the superposition principle, meaning you can simply add the electric field of both plates.

4. Dec 11, 2011

### ehild

You gave hints to get the electric field strength between the plates. Is not the force between the plates asked?

ehild

5. Dec 11, 2011

### I like Serena

@ehild: Yep, you're right. :)

So take one plate, say Q1, and calculate the electric field.
Then multiply by the charge of the other plate Q2.
The result is the force (F=qE) that Q1 exerts on Q2.

6. Dec 11, 2011

### khfrekek1992

Wow!! Thank you so much Delphi51, I Like Serena, and ehild! This makes so much sense now, the problem is a lot easier than I thought it would be... (Sorry I wasn't on for so long after I posted the question.) But thank you so much for all the help! That helps so much! :) You guys rock!