Coil Current Direction when Power is Interrupted (1)
A simple circuit is demonstrated to show that Current does NOT reverse when power to a coil is interrupted.
The coil “fights” changes in its magnetic field by attempting to keep current flowing in the _same_ direction as when it was powered. This is why the reverse-biased LED flashes when power to the coil is interrupted. The LED is only reverse-biased when the power to the coil is ON ! The _voltage_ polarity of the coil can be thought of as reversing, in order to keep the _current_ flowing in the same direction as it was when the coil was powered. Hence when the power to the coil is interrupted, the LED is no longer reverse-biased and the current continues to flow in the same direction out of the coil, thru the LED and back into the coil until all the stored energy is dissipated in the LED and the ohmic resistance of the wire.
NOTE: Please watch in the highest resolution available so that the flashes show up well. Low-res playback may cause frames to be dropped and might lose the flash.