How Solenoids Work

Generating a Controlled Magnetic Field

A solenoid is a device that creates electromagnetism after it has been electrified. Solenoids consists of a coil and a movable iron core called the armature. When current flows through a wire, a magnetic field is set up around the wire. If we make a coil of many turns of wire, this magnetic field becomes stronger, flowing around the coil and through its center in a doughnut shape.

Magnetic Field
When the coil of the solenoid is energized with current, the core moves to increase the flux linkage by closing the air gap between the cores. The movable core is usally spring-loaded to allow the core to retract when the current is switched off. The force generated is approximately proportional to the square of the current and inversely proportional to the square of the length of the air gap.

Different systems need different types of solenoids. Jameco offers a variety of solenoids, which transform an electrical input signal into motion, in a range of sizes and voltages. There are many applications in today's industries where different magnetic fields, coils resistance and amps are needed. Solenoids valves are also common for pneumatic and hydraulic systems to control various mechanical actuators.


Made of solid state, durable materials, these solenoids, or actuators, are used in machine tools, industrial machinery, and computer parts like disk drives and printers. Available as open frame, tubular or pull-type models.

Image Credits: Geek3 - Own work, CC BY-SA 3.0