Question

The relative dielectric constant of polystyrene is 2.5. What is the polarization produced when 0.5 mm thick sheet of polystyrene is subjected to 220 V?

(a) 2.78 X 10^-6 C/m

(b) 3.91 X 10^-6 C/m

(c) 4.12 X 10^-6 C/m

(d) 5.84 X 10^-6 C/m

I had been asked this question in class test.

Question is from Dielectric Polarisation topic in division Dielectrics of Engineering Physics II

Answer 1

Right choice is (d) 5.84 X 10^-6 C/m

Easiest explanation: We know, Polarization, P = εo(εr – 1)E

 Here, εr = 2.5

E = V/d

= 220 / 0.5 X 10^-3

= 4.4 X 10^5 Vm

εo = 8.85 X 10^-12 C/Vm

Hence, P = 8.85 X 10^-12 X (2.5 – 1) X 4.4 X 10^5 C/m^2

= 5.84 X 10^-6 C/m.