Given, the charge stored by the capacitor is Q and voltage is V. Let the capacitance of the capacitor is C.

The capacitance of a parallel plate capacitor is given by,

C=ε0Ad

Where,

ε0 is the permittivity of free space,

d is the distance between the plates of the capacitor,

A is the area of the plates

If we double the area and distance between the plates, then the capacitance will become like the equation given below,

⇒ C = ε02A/2d

⇒ C = ε0A/d

The above equation shows that there will be no effect on the capacitance of the parallel plate capacitor.

If C is constant and Q is constant, V will also be constant. By the formula, E = V/d

We can say that Electric field changed.

Hence, Energy density, Ud = 1/2ε0E2 will change.

We have seen that there will be no effect on the capacitance if we double the area and the distance between the plates of the capacitor.