To paraphrase Webster
, a solenoid
is an electromagnet
made out of a wire
wound around a tube
. A bar of iron
sits partially inside the tube. Run some current
through the wire, and it will pull the bar into the tube. Voila
, you have harnessed the electron
to provide some axial force
. Usually there's some sort of spring
that pulls the bar back out when you're done applying the juice
If you've been in an arcade, then you've seen solenoids at work in the moving parts of a pinball machine. If you've been in prison, you've seen solenoids at work in the electronic lock on your cell.
Don't ever try to drive a solenoid with alternating current. If you're lucky, it will scare you with the frenzied clacking of the bar against the tube. If you are unlucky, it will catch fire and burn down your house.