# Total Excess Charge using a Coulomb Balance

1. Nov 13, 2011

### ZedCar

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

If conducting a Coulomb Balance experiment, and a question asks to estimate the total excess charge on a sphere with a conducting surface charged to 2,000,000V potential.

Is there a specific equation I should be using to estimate this?

Thank you.

P.S. why are spheres used in such an experiment, and not some other shape?

Last edited: Nov 13, 2011
2. Nov 13, 2011

### rude man

V = q/R
'cause they make the math easy.

3. Nov 13, 2011

### ZedCar

Is it not C = 4∏ε0r

(Sorry for large font, I was trying to obtain a small 0 beside ε!)

4. Nov 13, 2011

### rude man

Yes, sure. In either case though you have to know the value of r.

(I assume you got the right formula for C of a sphere.)

Last edited: Nov 13, 2011