# Seemingly easy electric potential problem

1. Feb 16, 2005

### bemigh

Hey everyone, check out this question:

Two point charges each of magnitude 2.14 µC are located on the x axis. One is at x=1.39 m, and the other is at x=-1.39 m. Determine the electric potential on the y axis at y=0.505 m

Alright, so im working on it, as you do, but then i realized, that the original point charges, the MAGNITUDE of the charges is given. This causes problems. Because then the direction of electric field at the point on the Y axis can have many different directions (when the charge of the original points change). For instance, if both charges are positive, the electric field at the point on the Y axis is 6007.36 N/C, however, if one of them is negative, the field is now 16535.14 N/C (when you add the sum of the vectors, etc etc...

Anyone have any insight??
Cheers
Brent

2. Feb 16, 2005

### gnome

Potential is a scalar quantity, not a vector. But of course it does matter whether the charges are positive or negative. The wording is a bit ambiguous, but I'd assume they mean both are positive. Otherwise, what could you say about the potential along the y axis?

3. Feb 17, 2005

### bemigh

Hey, Brent again,
I understand what you mean, the potential should be equal all along the Y axis, because along every point of the axis, it is equidistant to each charge. I stll cant seem to find the answer...
Cheers

4. Feb 17, 2005

### gnome

This is worth repeating, 'cause you seem to be overlooking it:

Potential is a scalar quantity, not a vector.

What are you doing with vectors?

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