Question

Show that the mechanical force per unit is directly proportional to charge density.

Answer 1

Since we know that the mechanical force per unit area is $\frac{{\sigma }^2}{2{ϵ}_{0}k}$
Here k is a dielectric constant and ${ϵ}_0$ is also a constant so the mechanical force is direclly proportional to surface charge density
$\because f\propto {\sigma }^2$

$\therefore f\propto \sigma$