|MadSci Network: Physics|
Hello JWells: As soon as you remove the coil DC voltage, its magnetic field collapses. For all practical purposes the collapse occurs at the speed of light (exactly in a perfect vacuum). During that extremely small period of time, the collapsing field induces an equal but opposite voltage in the coil. If you were to look at it with an oscilloscope all you see would be a sharp reverse voltage spike. By the way if you do an Internet search on Michael Faraday you will pick-up a thread of historical experimentation and discovery concerning magnetic fields and induction phenomena. I looked briefly in the web and found a couple of sites you may wish to examine: I hope this answers your question. MAD.SCI MICRO
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