Question

Two small balls having equal positive charge Q C on each are suspended by two insulating strings of equal length L metre, from a hook fixed to a stand. The whole setup is taken into space where there is no gravity (state of weightiessness). Then the tension in the string is

• A. $\frac{1}{4\pi {ϵ}_0}\frac{q^2}{4L^2}$
• B. $\frac{1}{4\pi {ϵ}_0}\frac{q^2}{L^2}$
• C. $\frac{1}{4\pi {ϵ}_0}\frac{\sqrt{2}{q}^2}{L^2}$
• D. $\frac{1}{4\pi {ϵ}_0}\frac{q^2}{2L_2}$

Answer 1

The correct option is A $\frac{1}{4\pi {ϵ}_0}\frac{q^2}{4L^2}$

$F=\frac{1}{4\pi {ϵ}_0}\frac{q^2}{(2L{)}^2}$
$T=\frac{1}{4\pi {ϵ}_0}\frac{q^2}{4L^2}$
Since no gravity, two strings becomes horizontal, the electrostatic force on one charge due to the other balances with tension in the string.