- #1

Parad0x88

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## Homework Statement

Four charges, q1=+q, q2=-q, q3=+q and q4=*q are at the corners of a square with the side a=7.5 cm. (In such way that if one travels along the perimeter of the square, the charge signs are alternating.) If q=3.0 μC, what is the total energy required to assemble this system of charges? Comment on the sign of your answer.

## Homework Equations

U = Ke ((q1q2/r12) + (q1q3/r13) + (q1q4/r14) + (q2q3/r23) and so forth)

## The Attempt at a Solution

Correct me if I'm wrong, but I believe I simply have to sum up the energy between the points one by one and multiply by Coulomb's constant, and it will give me the total potential energy?