The capacity in a parallel plate condenser with air between its plates is C0=kε0Ad
If the air between the plates is replaced by glass than
C=5kε0d
C=5C0
Energy stored in a parallel plate condenser with air between its plates is W0
W0=12CV2
When glass is inserted between the plates then energy stored is
E=12×5C0×V2
E=5W0
Both the values of
capacitance and energy stored after inserting glass will increase.