# Homework Help: Electric field

1. Nov 23, 2007

### chopticks

The problem statement: Determine the maximum electric field on the axis of a ring of charge 4.3mC. The radius is 4cm.

I think the key is to use ekvation 1 and derivate to determine the maximum electric field but I'm not sure. Q is the charge, x is axis of the ring, a is the radius. Any suggestion?

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• ###### ekvation 1.jpg
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Last edited: Nov 23, 2007
2. Nov 24, 2007

### Shooting Star

Correct eqn. Differentiate and equate to zero to get the reqd x.

3. Nov 24, 2007

### chopticks

instead of differentiate, I plot the function in an graph. accodring to the graph there is only on max point where x is approx 0.12m and the electric fields is 4.246*10^18N/C. The electric field is etremley high but since the charge of the ring is 4.3mC it is quite reasonable. Is it physical correct reason?

4. Nov 24, 2007

### Shooting Star

x= a/(sqrt 2) at the pt of maximum.

5. Nov 24, 2007

### chopticks

now I get the same answer as you=), thanks alot!