Why outlets spark when unplugging - EMF & Inductors

What numbskull complains that a physicist hasn't been playing with liquid oxygen?  LOX is a common enough toy for chemists, but it is not required for a physics degree.  Sure... it's fun!... but hardly necessary.  For physics demos, compressed CO2, dry ice and liquid nitrogen would be cheaper and a lot safer as general coolants or propellents. " LOX makes stuff go *BOOM!*"