Question
Explain briefly how a capacitor stores energy on charging. Obtain an expression for the energy thus stored.
Solution
When the capacitor is connected to a battery, charges from one plate of the capacitor are transferred to another plate of the capacitor.
The work done by the battery in charging the capacitor plates is referred to as the electrostatic potential energy. Since, electrostatic force is conservative, this work is stored in the form of the potential energy of the system. This energy is released when, the capacitor discharges.
Let, a capacitor be gradually charged.
Potential of the capacitor at any stage is given as,
Small amount of work done dW in giving an additional charge dq is
Total amount work done in giving a charge Q to the capacitor is
Thus, energy stored in a capacitor is given by
The work done by the battery in charging the capacitor plates is referred to as the electrostatic potential energy. Since, electrostatic force is conservative, this work is stored in the form of the potential energy of the system. This energy is released when, the capacitor discharges.
Let, a capacitor be gradually charged.
Potential of the capacitor at any stage is given as,
Small amount of work done dW in giving an additional charge dq is
Total amount work done in giving a charge Q to the capacitor is
Thus, energy stored in a capacitor is given by
