(a) An air filled capacitor is given a charge of 2 µ C raising its potential to 200 V. If on inserting a dielectric medium, its potential falls to 50 V, what is the dielectric constant of the medium?
(b) A conducting stab of thickness‘t’ is introduced without touching between the plates of a parallel plate capacitor separated by a distance d (t < d). Derive an expression for the capacitance of a capacitor?