# Voltage and direction

1. Feb 12, 2012

### mm2424

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

What is the net electrical potential at point P due to the four particles if V = 0 at infinity, q = 5 fC and d = 4 cm? The image for this problem can be seen at http://www.webassign.net/hrw/hrw7_24-33.gif

2. Relevant equations

Potential = 1/(4εpi) * q/r

3. The attempt at a solution

I was able to answer this question, and the answer agrees with the answer key. However, it's left me a bit confused. Potential is a scalar, correct? How does one interpret the meaning of the voltage for point P if, say, only the two +q charges were present. Do the voltages cancel out, or do they add up? I ask because, when I answered this problem, I just blindly added up all the potentials at point P from each charge, regardless of the charges' location. I added the pluses, subtracted the minuses, and got the right answer (which ends up being .54 mV). But does that mean that there is a net positive attraction for the particle? I don't see how that makes sense, since the electrical fields from the positive charges should cancel, no? I imagine I'm looking at this the wrong way...any help would be greatly appreciated!

2. Feb 12, 2012

### Staff: Mentor

3. Feb 12, 2012

### mm2424

So if you had a point that was equidistant between two equal positive charges q, the voltage would be positive and not 0?

4. Feb 12, 2012

### Staff: Mentor

Yes. The potential (a scalar) would be the sum of the contributions from each charge, both of which are positive.