Three charges Q, `+q and +q` are placed at the vertices of an equilateral triangle of side l as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal

Options

A. `-q`
B. `+q`
C. Zero
D. `-(q)/(2)`

Answer

D

Explanation

P.E of system `=U=(kQq)/(l)+(kq^(2))/(l)+(kqQ)/(l)=0, (kq)/(l)(Q+q+Q)=0`
`2Q=-q i.e.,Q=(-q)/(2)`