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Old 02-25-2009, 08:22 AM
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nilrehob nilrehob is offline
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Join Date: Nov 2008
Location: Sweden
Posts: 689
Aaron, I'm not convinced.

I don't have much personal experience, yet, but reading in the (in my opinion very good) 2'nd edition (which has much more theory than the 1'st edition) of "Practical Electronics for Inventors" (how could You resist such a title),
I stay with my conclusion in my previous post.
In the book, Paul Scherz uses the terms "back" and "forward" Emf to separate the two events increasing and decreasing the current.
The average voltage V over an ideal coil when the current drops I amps in t seconds is V=L*I/t and would be a spike with infinite voltage if the decrease in current is instant.
But infinite spikes never happens, of course, as a real coil has both resistance and capacitance,
but they can be quite big, as we all have observed.

The reaction in capacitors and batteries when receiving a forward Emf spike is quite fortunate as the are able to collect the energy in it.
Hob Nilre
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