Class 12 Physics - Chapter Electrostatic Potential and Capacitance NCERT Solutions | The plates of a parallel plate capacitor

Welcome to the NCERT Solutions for Class 12th Physics - Chapter Electrostatic Potential and Capacitance. This page offers a step-by-step solution to the specific question from Excercise ".$ex_no." , Question 26: the plates of a parallel plate capacitor have an a....
Question 26

The plates of a parallel plate capacitor have an area of 90 cm2 each 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 electrostatic 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.

Answer

Area of the plates of a parallel plate capacitor, A = 90 cm2 = 90 × 10 - 4 m2

Distance between the plates, d = 2.5 mm = 2.5 × 10 - 3 m

Potential difference across the plates, V = 400 V

(a) Capacitance of the capacitor is given by the relation,

Electrostatic energy stored in the capacitor is given by the relation,

Where,

= Permittivity of free space = 8.85 × 10 - 12 C2 N - 1 m - 2

Hence, the electrostatic energy stored by the capacitor is 2.55 x 10-6 J

(b) Volume of the given capacitor,

Energy stored in the capacitor per unit volume is given by,

Where,

= Electric intensity = E

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