Question

A 5.06 10-5 H solenoid is constructed by wrapping 70 turns of wire around a cylinder with a cross-sectional area of 8.10 10-4 m2 When the solenoid is shortened by squeezing the turns closer together, the inductance increases to 8.22 10-5 H. Determine the change in the length of the solenoid.

Answer 1

Answer 2

inductance is given by L = u * N^2 * A/l

L = 5.06*10^-5, N = 70 , A = 8.1*10^-4

so l = 70*70* 8.1*10^-4/5.06*10^-5

l = 9.85 cm

l' = 70*70* 8.1*10^-4/8.22*10^-5

= 6.065 cm

so change in length = 3.785 cm