CBSE Class 12-science Answered

After disconnecting battery let us assume the charge on the plates is Q and the potential difference is V.

The relation connecting capacitance C, charge Q and potential difference V is given by C = Q/V.

 

when dielectric material is inserted between parallel plates the capacitance increases and the new capacitance C' is given by C' = k×C, where k is dielectric constant.

Charge Q remains same.

Hence potential difference reduces and the new value of potential difference is V/k .

 

Energy stored in the capacitor before inserting dielectric  = (1/2)×C×V²

 

after inserting dielectric, energy available in the capacitor = (1/2)×(kC)×(V/k)² = k×(1/2)×C×V²