Purpose: To demonstrate that a time-dependent B field through a coil induces a current in the coil.

Two galvanometers, a low frequency oscillator, two solenoids which fit into one another, and an iron rod.

Attach the galvanometer and small coil to the oscillator (oscillator frequency below 1 Hz) and point out that the current is oscillating in the small solenoid producing a time dependent field in the solenoid. Then place the small solenoid in the large solenoid and the students can see that a current is now oscillating in the large solenoid. If you strain your imagination, you can see that the current in the large solenoid is 90^o out of phase with the current in the small solenoid (a strobe light triggered by the oscillator would be nice at this point). Finally, place the iron rod in the two solenoids to demonstrate the effect of increasing the permeability of the core.

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