Function
While AC and DC solenoids use different types of current, they both work in the same basic manner. When the insulated, coiled wire of the solenoid receives electrical current, the magnetic field produced strongly attracts the iron or steel rod. The rod, which is attached to a compression spring, moves into the coil and will remain there until the current is stopped, keeping the spring under pressure the entire time. When the current is turned off, the compressed spring forcefully snaps the rod back into its original position.
The force created by the spring on the rod is what makes the solenoid useful in devices that rely on a number of different parts that must be activated quickly in succession.