Physics

Problem

Four point charges are fixed at the corners of a square of side

0.20\,\text{m}

. Charges of

+5.0\,\mu\text{C}

are located at three consecutive corners, and a charge of

-5.0\,\mu\text{C}

is located at the fourth corner. Determine the total electric potential energy of the system. a)

+6.1\,\text{J}

-1.6\,\text{J}

0\,\text{J}

+3.0\,\text{J}

Intuitive explanation

The key is recognizing that electric potential energy depends on every pair of charges in the system, not just one charge interacting with others. You'll sum the potential energy $U = k\frac{q_1 q_2}{r}$ for all six unique pairs—three sides of the square, two diagonals, and one more side—being careful about which distances apply and that opposite charges contribute negative energy. The geometry of the square determines exactly which pairs are separated by the side length versus the diagonal length.

Intuitive explanation

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