Question

Three charges are placed at the vertices of equilateral triangle of charge $q$ each. What is the net potential energy, if the side of equilateral $\Delta$ is $l ?$

• A. $\frac{1}{4 \pi \varepsilon_{0}} \frac{q^{2}}{l}$
• B. $\frac{1}{4 \pi \varepsilon_{0}} \frac{2 q^{2}}{l}$
• C. $\frac{1}{4 \pi \varepsilon_{0}} \frac{3 q^{2}}{l}$
• D. $\frac{1}{4 \pi \varepsilon_{0}} \frac{4 q^{2}}{l}$

Answer 1

Answer: (C)

$U=\frac{1}{4 \pi \varepsilon_{0}} \cdot \frac{Q_{1} Q_{2}}{r} ;$ net potential energy is
$U_{ net }=3 \times \frac{1}{4 \pi \varepsilon_{0}} \cdot \frac{q^{2}}{l}$