I read an article from wikipedia about freewheeling (flyback) diode which is used to drive a relay. I understand it but I have four questions. Would you give me a hand, please ?
1- Why does the coil change its polarity ?
In figure 1 the positive terminal of the coil is the upper terminal (at node 1), but in figure 3 the positive terminal of the coil is the lower terminal ( at node 2). that means it discharge in the opposite direction. If it was a capacitor the polarity would not change.
2- If I apply AC to a coil, Does the voltage spike happen each period when the voltage is zero ?
I read that the coil makes a voltage spike when we turn off the supply. does that mean the coil make spikes at the arrows of the following figure?
3- Why don't we put a diode for each inductive load such as motors in children toys .. etc. ?
4- Can I put an LED rather than a diode ?
Thank you very much,