# Homework Help: Potential energy of electricity

1. Oct 19, 2015

### Calpalned

1. The problem statement, all variables and given/known data
I don't understand the answer to part b

2. Relevant equations
n/a

3. The attempt at a solution

The solution guide skipped too many steps. How was this derived? If the 5th charge is in the middle, it will be equidistant (about $\frac {b\sqrt {2}}{2}$) from each of the other four charges. Did they add up all of the potential energies or do something different? SImply put, I need to see the steps that led to this final answer. Thank you.

2. Oct 19, 2015

### Staff: Mentor

They added all the potential energies resulting from the new charge's proximity to the existing four charges. Your distance value is good. So just sum the four contributions.