Son of Transformer

Just when you thought it was safe to go into the electricity section again! This exhibit is a sequel to "Transformer", recipe # __. This exhibit has an exposed iron core with primary and secondary coils wound around it. The primary is supplied with a source of DC current through a visitor operated switch. The secondary is connected to a light bulb. The visitor notices that the light only flashes when the current changes, ie. is rising or falling. A spring loaded steel hinge is attracted to the iron core when current is flowing through the primary (making the core into an electromagnet. The visitor can easily see that even though the steel is attracted to the core, the light isn't lit unless the current (and hence the magnetic field) is changing.

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