What Is a Solenoid and How Does It Work?

In its most basic form, a solenoid is a coil of wire that is wound around a core. Generally, the core has two parts, which consists of a stationary core and a moveable armature, with both parts being spring-loaded. When an electrical current is introduced, a magnetic field moves the armature away from the stationary core or towards it, depending on the solenoid’s use and construction. When the current stops, the spring brings the armature back to its original position.

For a solenoid to work, it must have three things: a coiled wire, a moveable armature, and electricity. The coil is made of a tightly wound copper wire that is composed of many turns. The moveable armature, on the other hand, is attracted to the generated magnetic field, providing the necessary mechanical force to do work. Lastly, while not mentioned above, there is also a housing made of iron or steel that surrounds the coil to concentrate the magnetic field. While a solenoid takes advantage of electromagnetism, it is not an electromagnet. Despite this, many people use these terms interchangeably.

What Is a Solenoid Valve?

Solenoid valves are like any other valve in that they are tasked with regulating the flow of gasses or liquids. The presence of a solenoid in the valves enables them to open or close via electricity. These types of valves are either normally open or normally closed. In the rest position, or “off” position, no current makes its way through the wires, and the moveable core rests against the base of the valve. This seals the valve, so that the liquid or gas behind it cannot get through.

As electricity runs through the coil of wire and creates the magnetic field, the core lifts up, allowing the liquid or gas to pass through the valve freely. Obstructing the flow of electricity, drops the core back down, closes the valve, and cuts off the flow of a gas or liquid. A normally open solenoid valve works in a reverse manner. In the off position, the core remains in the up position, enabling media to flow through the open valve. Meanwhile, powering the valve on will make the core move down, shutting off the flow and closing the valve.

The Strength of a Solenoid

If you are familiar with pneumatic tools, then you have used a small solenoid. The compressor has pressurized air in it, and when the trigger of a nail gun is pressed, a puff of compressed air is utilized to drive a nail into the material at hand. In doing so, a solenoid valve opened up for a fraction of a second, so that a little bit of pressurized air shoots from the compressor to the gun and drives the nail. The power that sources from the solenoid comes from the number of coils or turns in the wire and the current set through it.


Depending on the application, stronger and weaker solenoids exist for a variety of operations. For example, a large solenoid with many coils and a large electrical current may be unnecessary for making your doorbell ring. Instead, a small solenoid can be used. There are a variety of solenoid types that are categorized by their operation, those of which include electric, pneumatic, and hydraulic variations.

Testing a Solenoid

Diagnosing problems with your solenoid should be done early on to ensure that it is always working optimally. Since solenoids run on electromagnetism, there will not be a magnetic field surrounding it if the solenoid is not functioning properly. To test a solenoid, you can utilize a compass. Place the compass near the solenoid and activate the solenoid. If there is a problem activating the solenoid, there must be a mechanical issue. If the compass needle jerks, the solenoid can create a magnetic field. If not, then the solenoid is not getting ample electricity.

Other issues can be determined with a multimeter. Before using this instrument, check all the connectors first. If the positive or negative terminals are disconnected or appear faulty, the solenoid will not work. Once you have made this determination, switch the multimeter over to its resistance setting. Any reading over 0.3 ohms means that the unit is not working as it should.


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