Question

When an isolated sphere is given negative charge, then it's mass is ?

Answer 1

very negligibly increase as mass of electron is v v small

Answer 2

As per the question , negative charge is given to an isolated sphere.

We know that mass of electron is very less as compared to mass of proton,

The mass of electron  $[M_{e} ]=9.1*10^{-31}\ kg$

When negative charge is given to the sphere, there will be apparent increase in its mass which is very negligible.

Let n number of extra electrons are given to the sphere.

The initial mass of the sphere is M.

The mass of the sphere when electrons are given to it will be-

                             M' = M + [n×Me]

Hence, the mass of the sphere is increased apparently.