The battery is now disconnected from the plates and the separation of the plates is doubled ( = 0.78 cm). What is the energy stored in this new capacitor?

The energy stored in this new capacitor is

Explanation:

Suppose, Two parallel plates, each having area A = 2180 cm² are connected to the terminals of a battery of voltage as shown. The plates are separated by a distance d = 0.39 cm.

We need to calculate the charge

Using formula of capacitance

Put the value into the formula

The distance between the plates is doubled.

We need to calculate the new capacitance

Using formula of capacitance

Put the value into the formula

We need to calculate the energy stored in this new capacitor

Using formula of energy

Put the value into the formula

Hence, The energy stored in this new capacitor is

1.

it is the second option.