Question

What is the dielectric constant of the medium if the capacitance of a parallel plate capacitor increases from 40F to 80F on introducing a dielectric medium between the plates?

(a) 20

(b) 0.5

(c) 2

(d) 5

This question was addressed to me in a national level competition.

My question is based upon Effect of Dielectric on Capacitance topic in section Electrostatic Potential and Capacitance of Physics – Class 12

Answer 1

Correct choice is (c) 2

To elaborate: Capacitance without dielectric = 40 F.

Capacitance with dielectric = 80 F.

k = \(\frac {80}{40}\)

k = 2.