When the electric current is halted, the magnetic field also disappears, so electromagnets can be turned on and off at the flip of a switch.
(the electric current; is halted; ) (the magnetic field; disappears; T:When the electric current is halted) (electromagnets; can be turned on; L:at the flip of a switch)
the electric current the magnetic field electromagnets
is halted disappears can be turned on
T:When the electric current is halted
L:at the flip of a switch