Q.Write a short note on 'electrostatic shielding'.

If a conductor has a hollow cavity carved out of its interior, the electric field inside that cavity is exactly zero, provided no charge is deliberately placed inside the cavity itself -- and this remains true no matter how strong an external field is applied to the outside of the conductor, and regardless of the cavity's or the conductor's shape. This follows from Gauss's law combined with the fact that the field inside the solid part of any equilibrium conductor is already zero: any external field induces compensating charge on the conductor's outer surface that cancels the field throughout the conducting material and consequently leaves the enclosed cavity completely field-free as well. This complete blocking of external fields is called electrostatic shielding, and it is the operating principle of the Faraday cage, widely used to protect sensitive electronic instruments (and vehicle or aircraft occupants) from external electric fields, radio interference, and lightning, by diverting the field entirely around the shielded interior region rather than allowing it to pass through. …