Question

Two small spheres each having the charge $+Q$ are suspended by insulating threads of length $L$ from a hook. This arrangement is taken in space where there is no gravitational effect. Then the angle between the two threads at the point of suspension and the tension in each thread will be

• A. ${180}^{\circ },\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{(2L{)}^2}$
• B. ${90}^{\circ },\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{L^2}$
• C. ${180}^{\circ },\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{2L^2}$
• D. ${180}^{\circ },\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{L^2}$

Answer 1

The correct option is A ${180}^{\circ },\frac{1}{4\pi {\epsilon }_0}\frac{Q^2}{(2L{)}^2}$

The position of the balls in the absence of gravitational force will become as shown below


Thus angle $\theta ={180}^{\circ }$ and
force $F=\frac{1}{4\pi {\epsilon }_0}.\frac{Q^2}{(2L{)}^2}$.