Electrostatics Question 376
Question: Two equal charges $ q $ are placed at a distance of $ 2a $ and a third charge $ -2q $ is placed at the midpoint. The potential energy of the system is [MP PMT 1997]
Options:
A) $ \frac{q^{2}}{8\pi {\varepsilon _{0}}a} $
B) $ \frac{6q^{2}}{8\pi {\varepsilon _{0}}a} $
C) $ -\frac{7q^{2}}{8\pi {\varepsilon _{0}}a} $
D) $ \frac{9q^{2}}{8\pi {\varepsilon _{0}}a} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ U _{system}=\frac{1}{4\pi {\varepsilon _{0}}}\frac{(q)(-2q)}{a}+\frac{1}{4\pi {\varepsilon _{0}}}\frac{(-2q)(q)}{a}+\frac{1}{4\pi {\varepsilon _{0}}}\frac{(q)(q)}{2a} $
$ U _{system}=-\frac{7q^{2}}{8\pi {\varepsilon _{0}}a} $
