Class 12 Physics, CBSE and UP Board, Electrostatic Potential and Capacitance, Chapter-2 Exercise 2.8, NCERT Solutions for Class 12 Physics
In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10⁻3 m² and the distance between the plates is 3 mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?
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Area of each plate of the parallel plate capacitor, A = 6 x 10-3 m2
Distance between the plates, d = 3 mm = 3 x 10–3 m
Supply voltage, V = 100 V
Capacitance C of a parallel plate capacitor is given by, C = ε0 A/d
Where,
ε0 = Permittivity of free space = 8.854 x 10-12 N-1m-2 C-2
Therefore C = (8.854 x 10-12 x 6 x 10–3)/3 x 10–3
= 17.71 x 10-12 F = 17.71 pF
So, charge on each plate of the capacitor
q = VC = 100 x 17.71 x 10-12 C = 1.771 x 10–9 C
Therefore, capacitance of the capacitor is 17.71 pF and charge on each plate is 1.771 x 10–9 C.