# Homework Help: Given Electric Potential Function Find where field is zero.

1. Feb 17, 2009

### disfunctlguru

1. The electric potential in a certain region is:
V = ax2 +bx +c

where a = 13V/m2
b = -16V/m
c = 59 V

Determine the postion where the electric field is zero. Answer in units of m.

2. Relevant equations

E = -$$\nabla$$V

3. The attempt at a solution

I know that the Electric Field is the negative gradient of the potential function. I then find that the partials with respect to y and z are zero. Then I find the partial with respect to x is: Ex=-13x+16
Then find the zero to be about 1.23. But it is apparently incorrect. Any help would be appreciated.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 17, 2009

### Staff: Mentor

Redo that derivative.

3. Feb 17, 2009

### disfunctlguru

Well the actual partial deriv. is 13x-16. Then I took the opposite to be used as the function of E.

4. Feb 17, 2009

### Staff: Mentor

Double check that.
What's the derivative of that function?

5. Feb 17, 2009

### disfunctlguru

Thanks, I can't believe I can do some other complex integration etc and mess up a simple deriv.... mind blowing.