A Genecon is an inexpensive hand-cranked dc electric generator. You can use it to charge a one-farad supercapacitor.1 If you stop cranking the handle, the capacitor will discharge, sending a current into the Genecon and thereby causing the handle to start turning as an electric motor. How does the current direction compare before and after you stop cranking the handle? How does the direction of the turning of the handle compare before and after you stop cranking the Genecon?
References
1.
A Genecon costs about $50 and a 1-F capacitor about $35. They are available from numerous scientific suppliers by searching the web.
2.
The resistance of a Genecon is 10 Ω and can be connected directly to an oscilloscope or voltmeter without the 51-Ω resistor. However, the resistor attenuates the sharp noise spikes near the troughs in Fig. 2 so that they are barely visible.
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The coils rotate 48 times faster than the handle according to http://www.austincc.edu/bechtold/Physics%20II%20Labs/Magnetism%20-%20Faradays%20law%20-%20genecon%20and%20transformer.doc.
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2014
American Association of Physics Teachers
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