# Homework Help: Point charges and potential

1. Feb 14, 2005

### thisisfudd

Three point charges are arranged at the corners of a square of side L. What is the potential at the fourth corner (point A), taking V = 0 at a great distance?

OK, I am very confused. First of all, Giancoli (my textbook) seems to explain how to do this for one point charge, but I am confused about doing this for three charges. Second, what do they mean by "at a great distance"? I am assuming I would want to use V = 1/4piE0 Q/r. So I am guessing that I would have to do some kind of vector deal? Help appreciated.

2. Feb 14, 2005

### thisisfudd

Um never mind. So I thought about this again and decided to use V=kQ/L for each point individually -- does that make sense? And then add them up to get V total. So I wound up with ((1/square root 2) +1) x kQ/L. My book says the answer is square root 2 x k x Q/2L (square root 2 + 1). I believe this is the same thing?

3. Feb 14, 2005

### dextercioby

That "taking V = 0 at a great distance" means that an infinity the potential is 0,which means that the potential is actually negative.So you'd have to add 3 negative #-s,that's all.

Daniel.