Question

A parallel plate capacitor of capacitance C is charged to a potential V . It is then connected to another uncharged capacitor having the same capacitance . Find out the ratio of the energy stored in the combined system to that stored stored initially in the single capacitor .

Answer 1

When the capacitor is initially charged, its energy is 1/2*c*v2= (q)2/2c

After it is connected to a capacitor of same capacitance, the charge gets equally distributed on both the plates,
energy becomes= (q/2)2/2c
​and for the two capacitor it becomes = 2*​ (q/2)2/2c = q2/4c

So the ratio comes out to be 1:2.