# Electric field from potential energy

1. Oct 15, 2008

### physstudent1

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

Consider uniform electric field. The values of the potentials at the points(0,0) (.5,0) are equal and 20V higher than the potential at (0,.5) The magnitude and direction of the electric field are:
a)0
b)40N/c j
c)-40N/c j

2. Relevant equations

3. The attempt at a solution
I know the answer is b because this is a problem for my exam review and we were given the solutions, I don't know how to get it though can anyone help?

2. Oct 15, 2008

### physstudent1

I think I know why. I am thinking that since the field points in the direction of decreasing potential it must go up and since Va-Vb = E(b)-E(a) you know the potential difference is 20. so 20=E(.5) (a=0) then divide out and get 40n/c j. Also you know that the field must be perpendicular to the x axis because as you move down the x axis the potential remains constant right? Can anyone verify this I have an exam tomorrow and I want to make sure I have the concepts right. Thanks.

3. Oct 16, 2008

### Redbelly98

Staff Emeritus
You're reasoning is correct.