1. The problem statement, all variables and given/known data How much work is required to assemble eight identical point charges, each of magnitude q, at the corners of a cube of side s? Note: Assume a reference level of potential V = 0 at r = infinity. (Use k_e for ke and q and s as necessary.) 2. Relevant equations V = E.s U = q.V V = kQ/s U = kQ^2/s F = kq^2/s^2 3. The attempt at a solution In my first attempt I drew the cube, and the point charges, and realized this was essentially similar if you drew a sphere around the cube, so we could take the centre of the cube as the central point for all the charges. So that distance (using pythagoras) would be x = 1/2*sqrt(3)*s Then I decided the work done would simply be 8 times kq^2/(x) i.e. (8k(q^2))/(1/2*sqrt(3)*s) However this answer is wrong and I'm not sure why it would be wrong. Looking for other possible ways, I was thinking calculating the work done to bring each charge individually to the vertex and doing a summation would be the solution, but this question is only worth 1 point so I'm thinking even though that could be right, this is not the way they want me to go ahead with this. So then I though since the work done is equal to the integral of the force x change change in distance that this would amount to U = 8 [itex]\int[/itex] kq^2/s^2 . ds But I'm not too sure how to go about it with this, for starters there wouldn't be any force required to put the first charge in place since there's nothing else there repelling it, and then the change in distance would be from infinity to the vertex, I'm not too sure how that would be expressed. What should I be trying to do?