The correct option is B UOn5/3
Let the charge on the solid sphere beQ and radius of the solid sphere beR
Self energy of a solid sphere U0=3kQ25R [k=14πε0]
⇒Q2=5RU03k
Let the charge on each small sphere be q and the radius of each smaller sphere ber.
Self energy of each smaller sphere U=3kq25r .....(1)
From conservation of charge, we can write that
q=Qn ...(2)
Given that, Solid sphere is made into n smaller spheres
Thus, the volume remains constant,
∴43πR3=n×43πr3
⇒r=(Rn1/3 ) .....(3)
From (1)) , (2) and (3) we can write that,
U=UOn5/3
Hence, option (b) is the correct answer.