A 900pF capacitor is charged by a 100V battery, how much electrostatic energy is stored by the capacitor?

Hint: The capacitor is a device in which electrical energy can be stored. It is the positioning of two-conductors generally carrying charges of equal magnitudes and opposite sign and separated by an insulating medium. The non-conductive region can either be an electrical insulator or vacuum such as glass, paper, air or a semi-conductor called a dielectric.
Formula Used: $E = \dfrac{1}{2}c{V^2}$

Complete answer:
It is given that,
Charged voltage = 100 V battery in a 900-pF capacitor
Now, we need to find the Electrostatic energy stored in the capacitor.
Electrostatic energy stored by the capacitor is given by the formula,
$E = \dfrac{1}{2}c{V^2}$
Where, ‘E’ is the Electrostatic energy, ‘c’ is the Charge and ‘V’ is the potential.
$\eqalign{
  & E = \dfrac{1}{2} \times 900 \times {10^{ - 12}} \times {100^2} \cr
  & \therefore E = 4.5 \times {10^{ - 6}}J \cr} $
Thus, $4.5 \times {10^{ - 6}}J$ of electrostatic energy is stored by the capacitor.
Hence, a 900pF capacitor which is charged by a 100V battery, stores $4.5 \times {10^{ - 6}}J$ of electrostatic energy in the capacitor.

Additional Information:
Capacitors are used for various purposes such as:
1) It is used as a sensing device.
2) It is used in the audio system of the vehicle.
3) It is used for storing electrical potential energy such as batteries.
4) It is also used to separate AC and DC.

Note:
We know that electric energy can be stored in capacitors. But what we need to remember is how energy is stored in a capacitor. In order to store energy in a capacitor work has to be done to transfer the charges onto a conductor, against the force of repulsion from the already existing charges on it. This work is stored in the form of the potential energy of the electric field of the conductor.