How does a solenoid work?
Follow the link between coil current, magnetic force and the moving plunger.
Electromagnetism · Actuators
What is a solenoid?
A solenoid is a coil of wire that produces a magnetic field when current flows through it. In a solenoid actuator, that field moves an iron plunger. This diagram shows a DC pull-type actuator with a return spring.
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How it works.
The coil, magnetic path and spring act together. Current creates magnetic attraction; the plunger moves when that force overcomes the opposing load. Switching off the supply does not make current disappear instantly. Its decay changes when the spring can return the plunger.
Energize the coil
Closing the switch connects the DC supply. The current rises over time because the coil has both resistance and inductance. Follow the current trace before comparing the motion.
Pull the plunger inward
Magnetic attraction draws the plunger toward a smaller air gap. Its movement changes the magnetic circuit, so electrical and mechanical readings are linked rather than separate animations.
Switch off and release
The stored magnetic energy needs a discharge path. As current and magnetic force fall, the return spring pushes the plunger back. Compare current decay with the position trace.
Take this figure with you.
Files are included with full library access.
- Interactive HTML
- Source files
- Readme & license
Why does flyback protection change the release?
A diode provides a path for current after switch-off. A higher-voltage clamp can make that current decay faster. The full illustration compares these paths with the same actuator. Its “None” setting still models a transistor avalanche clamp; it does not mean the voltage can grow without limit.
About this model
- This is a simplified DC actuator model, not a component-selection or circuit-safety calculator.
- The magnetic circuit neglects effects such as leakage flux; the displayed field shapes are explanatory.
- The public preview uses a recorded sequence. Full controls and the offline source package require library access.
Use the power, pause, step and reset controls. Compare the flyback options while watching current and plunger position.
Version 1.0.0
Frequently asked questions
Is a solenoid the same as an electromagnet?
The terms overlap, but describe different things: solenoid describes the coil, while electromagnet describes magnetism produced by electric current. This actuator adds a moving plunger and a spring to turn that magnetic effect into motion.
Does every solenoid return when power is removed?
No. This example uses a return spring. Other designs can use an external load or a permanent-magnet latch, so their release behavior is different.