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Electrostatic Potential And Capacitance

Question
CBSEENPH12037316

What is the area of the plates of a 2F parallel plate capacitor, given that the separation between the plates is 0.5 cm? [You will realise from your answer why ordinary capacitors are in the range of μF or less. However, electorlytic capacitors do have a much larger capacitance (0.1 F) because of very minute separation between the conductor.]

Solution
Given,
Capacitance of parallel plate capacitor, C=2F
Seperation between the parallel plate capacitor, d =0.5 cm =5 x 10
–3 m

Now, using the formula for capacitance of a parallel plate capacitor,
             C = ε0AdA = Cdε0                                      (ε0 =8.85 × 10-12 Fm-1)
   = 2×5×10-38.85 × 10-12

A = 1.13 × 109 m2    = 1.13 × 103 km2 = 1130 km2

Therfore, inorder to get the capacitance in Farads, the area of the plates should be in kilometres which, practically cause inconvenience. And, that is why, the ordinary capacitors are in the range of μF.

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