Question

Four equal electric charges are arranged at the four corners of a square of side $a$. Out of these four charges, two charges are positive and placed at the ends of one diagonal. The other two charges are positive and placed at the ends of the other diagonal. The energy of the system is:

• A. Negative
• B. Positive
• C. Less than $\frac{1}{4\pi {\epsilon }_0}\left(\frac{2q^2}{a}\right)$
• D. greater than $\frac{1}{4\pi {\epsilon }_0}\left(\frac{2q^2}{a}\right)$

Answer 1

Answer: (B), (D)

The correct options are
B Positive
D greater than $\frac{1}{4\pi {\epsilon }_0}\left(\frac{2q^2}{a}\right)$

Energy of the system=$\frac{4\left(k{q}^2\right)}{a}+\frac{2\left(k{q}^2\right)}{\sqrt{2}a}$

which is positive and greater then $\frac{2k{q}^2}{a}$