Energy stored in an electric field

Electricity and Magnetism Level 2

What is the energy stored in an arrangement of four point charges of magnitude $Q$ at the corners of a square of side-length $L?$

1.41 \frac{kQ^2}{L}

5.41 \frac{kQ^2}{L}

4 \frac{kQ^2}{L}

6 \frac{kQ^2}{L}

1 solution

Marcelo M
Apr 18, 2019

Enery stored in charges that share side:

U = k((Q^(2))/(L))

Since 4 pairs share side the energy is equal to:

U = 4k((Q^(2))/(L))

Energy stored in charges that share diagonal:

U = k*((Q^2)/√2L)

Since 2 pairs share diagonal:

U = 2 k ((Q^2)/√2L)

The total energy is equal to the sum of all the energys between pairs

Utotal = 5.41 k (Q^2/L)