Two identical metallic spheres A and B of exactly equal masses are taken. Sphere A is given positive charge Q columb and B is given an equal negative charge. So initially before the charge is given. What will be the masses after the charging?

We know from the property of equalization of charge, i.e.

$Q=ne$

where $n:$ no. of electrons.

Now, After A is given positive charge $Q$; n number of electrons are with drawn from it. Hence it's mass will reduce by $\left\{{nm}_e\right\}$ where {$m_e$ : mass of electrons}.

Similarly as $B$ is given negative charge $Q$; $n$ number of electrons are given to sphere $B$, hence its mass will increase by ${nm}_e$, where $m_e$: mass of electron.