A thin metallic shell of radius ‘a’ carrying a charge ‘-Q’ is concentrically placed inside another thin metallic shell of radius ‘2a’ carrying a charge ‘+Q’ now the two shells are connected by a then wire. Then select the correct option.

When the shells are connected by a wire the whole charge of  inner shell will flow to the outer shell. As a result charge on both shells will be zero. Since charge stored in the system is zero,  energy stored in the system is converted into heat energy.