(a) Define eddy currents.
(b) Using Lenz’s law, explain why the direction of an eddy current in a conducting sheet always opposes the external time-varying magnetic field producing it.
(c) A sensitive micro-controller circuit is housed inside a closed copper box. Explain, with reasons, how eddy currents in the box walls protect the circuit from a rapidly varying stray magnetic field present in the laboratory.
(d) State any two practical limitations that may arise if the same shield were made of a ferromagnetic material instead of copper.