why does a little ‘spark’ happen when you turn something on before plugging it in, but not when it’s turned off when you plug it in?

Question

I see this happen with my water boiler for example. When I turn it on before I plug it in there’s this spark that happens between the plug and the wall. When it’s turned off it doesn’t happen. Does the boiler ‘ask’, or know when to ask, for electricity?

In: Engineering

Answer 1

When off, the circuit isn’t complete and so no chance of sparks. When on, the circuit is complete and so the current can then travel from one side of the plug/prong, through the device, and out/back to the wall through the 2nd prong and when there is a little distance, the current can “jump” and create a spark.