Question

Net inward and outward flux of a closed surface are φ1 and φ2. What is the charge enclosed inside the surface?

(a) Zero

(b) -(∅1-∅2)εo

(c) (∅1-∅2)εo

(d) \(\frac {(\emptyset_1 + \emptyset_2)}{\varepsilon_o}\)

This question was addressed to me during an internship interview.

This is a very interesting question from Gauss’s Law in division Charges and Fields of Physics – Class 12

Answer 1

Correct option is (b) -(∅1-∅2)εo

The best explanation: The net outward flux from the surface is (∅2-∅1) = -(∅1-∅2). We know, according to Gauss’s Law, net outward flux coming out of a closed surface is \(\frac {1}{\varepsilon_o}\) times the charge stored in it. Therefore charge stored in the surface = εo*flux coming out of the surface = (∅2-∅1)εo.