Question

Find the inductance of a coil with permeability 3.5, turns 100 and length 2m. Assume the area to be thrice the length.

(a) 131.94mH

(b) 94.131mH

(c) 131.94H

(d) 94.131H

This question was addressed to me in an international level competition.

This key question is from Real Time Applications in section Electrostatic Fields of Electromagnetic Theory

Answer 1

The correct choice is (a) 131.94mH

The explanation is: The inductance is given by L = μ N^2A/l, where μ= μoμr is the permeability of air and the material respectively. N = 100 and Area = 3 X 2 = 6. L = 4π X 10^-7 X 100^2 X 6/2 = 131.94mH.