Question

A ring having a cross-sectional area of 500 mm^2, a circumference of 400 mm and ϕ=800microWb has a coil of 200 turns wound around it. Relative permeability of ring is 380. Calculate the reluctance.

(a) 1.68 * 10^-4A/Wb

(b) 1.68 * 10^4 A/Wb

(c) 1.68 * 10^6 A/Wb

(d) 1.68 * 10^-6A/Wb

The question was posed to me in quiz.

My query is from Ohm’s Law for a Magnetic Circuit topic in chapter Simple Magnetic Circuits of Basic Electrical Engineering

Answer 1

Right option is (c) 1.68 * 10^6 A/Wb

To explain I would say: Reluctance=l/(µ*A) = l/(µrµ0*A)

Substituting the values, we get Reluctance=1.68*10^6 A/Wb.