Question

Compute the conductivity when the current density is 12 units and the electric field is 20 units. Also identify the nature of the material.

(a) 1.67, dielectric

(b) 1.67, conductor

(c) 0.6, dielectric

(d) 0.6, conductor

This question was addressed to me in an interview.

My question is taken from Continuity Equation topic in chapter Electric Fields in Material Space of Electromagnetic Theory

Answer 1

Correct answer is (c) 0.6, dielectric

For explanation I would say: The current density is the product of conductivity and electric field intensity. J = σE. To get σ, put J = 12 and E = 20. σ = 12/20 = 0.6. Since the conductivity is less than unity, the material is a dielectric.