Question

Two charged particles with charge 2.0 × 10⁻⁸ C each are joined by an insulating string of length 1 m and the system is kept on a smooth horizontal table. Find the tension in the string.

Answer 1

Given:
Magnitude of the charges, q =  2.0 × 10⁻⁸ C
Separation between the charges, r = 1 m
The tension in the string will be same as the electrostatic force between the charged particles.
So,  

$$T=F$$

By Coulomb's Law,         

$$F=\frac{1}{4\pi {ϵ}_0}\frac{q^2}{r^2}$$

$$\Rightarrow T=\frac{9\times {10}^9\times {(2.0\times {10}^{-8})}^2}{1^2}$$ 

$$=3.6\times {10}^{-6}$$ N