A solenoid valve coil is designed to convert electrical energy into lateral motion. The coil usually consists of copper wire wound around a hollow bobine or tube, so when electric current flows through the coil, a magnetic field is generated. 

By placing a solenoid valve coil over a ferromagnetic core, the magnetic field generated causes the plunger to slide further up towards the magnetic field, thus allowing an opening to be created. This in turn can be utilized to either to control direct acting solenoid valves, assisted lift solenoid valves or servo/pressure assisted solenoid valves.