# Derive equations for Electric Field/Electric Potential

1. Feb 20, 2013

### Renaldo

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

(a)
A ring with charge Q and radius R is in the yz-plane and centered on the origin. What is the electric potential a distance x above the center of the ring? (Use any variable or symbol stated above along with the following as necessary: k.)

(b)
Derive the electric field from this relationship. (Use any variable or symbol stated above along with the following as necessary: k.)

2. Relevant equations

V = U/q
U = -qEr
E = kQ/r2

r = (x2+R2)0.5

3. The attempt at a solution

I got problem (a) correct. I combined the above equations which resulted in

kQ/r

kQ/(x2+R2)0.5

For (b), it wants the answer in i + j + k.

j and k are 0.

V = qEr/q
V = Er
E = V/r

E = kQ/r2

E = kQ/(x2+R2)

This is not the correct answer for i. The problem is due in 1 hour, 30 minutes.

2. Feb 20, 2013

### Renaldo

Well, it turns out that I was able to figure this one out just in time.