Reverse-Engineering a Hand-crank Flashlight

I picked up a $1 hand-crank flashlight at a Dollar Store. I thought it would be a good teaching material for an introductory physics course. In particular, it contains a magnet and a coiled wire for generating electricity.

This is what the internal components look like.  The handcrank turns the large gear.

The ring shaped magnet rotates by the hand-crank and a set of gears on top of a coiled wire.

Note that N and S poles alternate around the ring.

The magnet would sit on top of this spool of coil and rotate. You can see two ends of the wire sticking out. There are two cross-shaped metal posts. As the ring-shaped magnet rotates, these two metal posts will alternate between N and S poles, creating changing magnetic flux through the coil and generating emf, according to Faraday’s law.

Other interesting bits found inside were: a set of gears that makes the magnet rotate in one direction only.

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