Here's the question you clicked on:
tameist
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 = . (Use any variable or symbol stated above along with the following as necessary: ke.)
you start one by one .. you bring in the first charge.. no work is done.. you bring in now the second charge.. you are now did work in bringing this one.. that work is the potential at a distance 's' from the first charge times the charge itself.. now you bring in the third one.. you do more work .. due to two present charges.. its all about calculating the distances.. which is now math work :P