# Capcitance help

1. Apr 6, 2005

### XxXDanTheManXxX

A parallel plate capictor with a plate area of 1.8 m^2 and a seperation of 0.1 mm is charged to 200V.
a. what is the electric field bwt. the plates?
b. what is the energy/unit volume in the space between the plates?
c. Find the capacitance C
d. Calculate the total energy stored in this capacitor

2. Apr 6, 2005

### dextercioby

What are your ideas?

Daniel.

3. Apr 7, 2005

### XxXDanTheManXxX

I know how to find the capiciatnce in a parrallel but have no idea how to find out the electric field. Any help? I don't have a text book with me so I am pretty much screwed :)

4. Apr 7, 2005

### whozum

Do you know the electric field for a surface charge?

If so, a parallel plate capacitor is two charged surfaces with separation d. The field can be found by adding the field of each plate.

5. Apr 7, 2005

### Davorak

Use gauss's law in intgral form. Some times called the gaussian pilbox.
$$\int \vec{E}\cdot d\vec{A} =\frac{Q_{Enclosed}}{\epsilon_0}$$
Sove for the electric feild for one plate, then solve for the other plate and use vector addtion to add them together.

Use the elctric feild to find the voltage and the energy density.

Last edited: Apr 7, 2005
6. Apr 7, 2005

### GCT

can't get any easier than this, simply use equations in your text.