# Electric Field due to a Ring of Charge

1. Jul 9, 2006

### DarkWarrior

I've been stuck on this problem for awhile now..

At what distance along the central axis of a ring of radius R and uniform charge is the magnitude of the electric field due to the ring's charge maximum?

Now, I know that the equation for this problem is E = [k|qz|] / [(z^2+R^2)^3/2], which is the electric field magnitude of a charged ring. And to get the maximum, you have to find where the first derivative of the equation where it equals zero.

But when I take the derivative of the equation, I get a complete mess not even close to the answer. Can anyone give me some hints or a push in the right direction? Is my thinking incorrect? Thanks. :)

2. Jul 9, 2006

### neutrino

It's a straighforward problem, and your approcah is right. If you could just post your work, we can try to help you out.

3. Jul 9, 2006

### DarkWarrior

Thanks, confirming that I was going in the right direction was all I needed. I eventually did get the answer, but with some difficultly thanks to my poor algebra skills. :)

4. Sep 17, 2011

### goteamusa

In this problem we do not know E and we are looking for z correct? I do not know how to deal with this problem of having two unknowns. I am given R but that is all.