Question

Charges$-q,Q$ and$-q$ are placed at an equal distance on a straight line. If the total potential energy of the system of three charges is zero, then find the ratio $Q/q$ :

• A. $1/2$
• B. $1/4$
• C. $2/3$
• D. $3/4$

Answer 1

The correct option is B $1/4$

Potential energy of the system of 3 charges $U=U_{12}+U_{23}+U_{13}$

$U=-\frac{kqQ}{r}-\frac{kqQ}{r}+\frac{k{q}^2}{2r}=0$

or $Q/q=1/4$