Why outlets spark when unplugging - EMF & Inductors

It's really helpful intuitively if you compare this effect in the hydraulic sense.
Think of the inductor as a big heavy turbine wheel that gets spun up by water flowing through it.
When the flow of water is interrupted, and the circuit is opened, that turbine has A LOT of momentum still, yet it has nowhere to go, so it builds up a great deal of pressure, and energy is lost in the form of heat or something breaking.

Ever try pulling and releasing the string on a bow with no arrow? Don't. It'll shake itself to pieces and fracture because the energy it just stored has no outlet, and if you're holding it, YOU will be that outlet and it'll shake itself out of your hands.