# Calculating the capacitance problem

1. Oct 17, 2008

### ctpengage

1. The problem statement, all variables and given/known data
If an uncharged parallel-plate capacitor (capacitance C) is connected to a battery, one plate becomes negatively charged as electrons move to the plate face (area A). The depth d from which the electrons come in the plate in a particular capacitor is plotted against a range of values for the potential difference V of the battery. When d is one picometre, the potential difference is 20V. The gradient is equal to 5x10-14. What is the ratio C/A.

2. Relevant equations

q=ε₀EA
q=CV

3. The attempt at a solution

I combined the above two equations to get the expressions C/A=ε₀/D
However that doesn't provide me with a numerical solution for the ratio C/A.

Can anyone please help?

2. Oct 18, 2008

### Redbelly98

Staff Emeritus
I don't understand what is meant by "the depth ... from which the electrons come in the plate".

Also, what is this "gradient equal to 5x10-14" mean? And what are the units?

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