Question 26: NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

The plates of a parallel plate capacitor have an area of 90 cm² eacn and are separated by 2.5 mm.The capacitor is charged by connecting it to a 400 V supply
(a) How much electrostatic energy is stored by the capacitor?
(b) View this energy as stored in the electro-static field between the plates, and obtain the energy per unit volume u. Hence arrive at a relation between u and the magnitude of electric field E between the plates.