# How to locate Two spots where electric potential is zero

1. Nov 11, 2009

### crazuiee

1. The problem statement, all variables and given/known data
A positive charge of +q1 is located 3.00m to the left of a negative charge -q2. the charges have different magnitudes.
a) on the line through the center of the charges, the net electric field is zero at a spot 1.00m to the right of the negative charge. Determine the relative magnitude of the charges (charge ratio q1/q2)
b) on this line there are two spots where the potential is zero. locate these two spots relative to the negative charge.

2. Relevant equations
Ue=kq1q2/r
V=Ue/q
V=kq/r

3. The attempt at a solution
for part a i got q1=+16 and q2=-1
I'm not sure how to find these zero potential spots. I know they're supposed to be near the smaller negative value but I just can't figure out how to calculate out exactly where.

2. Nov 12, 2009

### Staff: Mentor

q1 and q2 are magnitudes and thus positive. You found that q1/q2 = 16. Good!
Write an expression for the total potential as a function of distance from the negative charge. You'll find it helpful to divide the line into 3 regions and write separate expressions for each region.

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