A large insulated sphere of radius r charged with Q units of electricity is placed in contact with a small insulated uncharged sphere of radius r' and is then separated. The charge on the smaller sphere will now be.

Options

A. `(Q(r'+r))/(r')`
B. `(Q(r'+r))/r`
C. `(Qr)/(r'+r)`
D. `(Qr')/(r'+r)`

Answer

D

Explanation

Let the charge on the smaller sphere be q. As the potential of both will be the same finally,
`q/(r.)=(Q-q)/r` or `q=(Qr.)/(r+r.)`