Question

In a long straight solenoid with cross-sectional radius a and number of turns per unit length n a current varies with a constant velocity I A/s. Find the magnitude of the eddy current field strength as a function of the distance r from the solenoid axis. Draw the approximate plot of this function.

Answer 1

We use B = μ₀nI

Then, from the law of electromagnetic induction

The meaning of minus sign can be deduced from Lenz's law.