A large insulates 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
(a) (Q(r’+ r))/r’
(b) (Q(r’+ r))/r
(c) Qr/(r’+ r)
(d) Qr’/(r’ + r)
Ans: (d)