# Finding charge of a uniformly charged disk

1. Nov 2, 2008

### minase

Along the axis of a uniformly charged disk, at a point 0.6 m from the center of the disk, the potential is 91.4 V and the magnitude of the electric field is 86.5 V/m; at a distance of 1.5 m, the potential is 46.8 V and the magnitude of the electric field is 27.0 V/m. Find the total charge residing on the disk.

I have both equation to finding the electric field and potential field for a uniform disk. There are two unknowns in the equation they are R and σ. Are they giving too much information?

2. Nov 3, 2008

### minase

I have the two equations here how do I go about solving this. After substuiting E ,v and x for both equations I can divide the two equation by each other. Is there any easier way to do this. It is a homework problem I don't want to lose point plz reply :)
$$E = 2k_e\pi\sigma(1-\frac{x}{\sqrt{x^2+R^2}})$$
$$V = 2k_e\pi\sigma\(x(\sqrt{1+\frac{R^2}{x^2}}-1)$$

Last edited: Nov 3, 2008