why is spark produced in the switch of a fan ,when it is switched off?
I have answered this in a similar question.
WHEN CURRENT IS SWITCHED OFF, A LARGE INDUCED e.m.f. IS PRODUCED IN THE GAP BETWEEN THE CONTACTS OF THE SWITCH AND THE LIVE WIRE. AS A RESULT OF THIS, A LARGE ELECTRIC FIELD IS PRODUCED WHICH IONISES THE AIR.(CORONA DISCHARGE) THIS ALLOWS THE CURRENT TO PASS THROUGH THE GAP FOR A SHORT INTERVAL OF TIME AND HENCE SPARK IS PRODUCED.https://www.meritnation.com/ask-answer/question/why-a-spark-is-produced-in-the-switch-of-a-fan-when-it/physics/5388097