Answer to Question #183949 in Electricity and Magnetism for KyKy

Question

Consider a spring used as a solenoid with a magnetic field of 0.25 T. (a) What is the magnetic field if the spring is stretched to twice its original length? (b) What is the magnetic field if the spring is compressed to half its original length and the current is increased to twice its original value?

Answer 1

Solution

For solenoid magnetic field is given by

$B=\frac{\mu_0 N I}{L}\propto\frac{1}{L}$

a. When length become twice then magnetic field become half.

b. Now if length become half and current become twice then magnetic field become four times from initially.