# Solenoids are Electromagnetic Devices

by Ron Kurtus (revised 7 February 2017)

A solenoid is a simple electromagnetic device consisting of a coiled electric wire, wrapped in a helix shape. When electric current is passed through the wire, the solenoid acts like a magnet with N and S poles at the ends of the helix.

Since it is hollow, a solenoid can draw an iron or ferromagnetic rod into the helix. This effect is handy in creating switching or locking devices.

Another use of a solenoid is in the creation of an electromagnet. When an iron rod is permanently placed inside the solenoid, the metal greatly increases the magnetic effect.

Questions you may have include:

• What is a solenoid?
• How can a solenoid be used as a switch?
• How does a solenoid become an electromagnet?

This lesson will answer those questions. Useful tool: Units Conversion

## Solenoid creates magnetic field

Winding a metal wire into a helix and passing electrical current through the wire results in the creation directed magnetic field, such that the ends of the helix or solenoid have N (north-seeking) and S (south-seeking) magnetic poles.

Current through solenoid creates magnetic field

(Image based on Wikimedia Commons image by Zureks)

## Uses of solenoids

The magnetic field of a solenoid can draw in an iron rod. What works even better is that it can draw in or push out a permanent magnet, depending on the directions of the magnet and the electrical current. This controlled action is useful in creating an electrical switch.

## Electromagnet

When an iron rod or other ferromagnetic material is placed within the solenoid helix, the rod becomes magnetized, thus creating an electromagnet.

The presence of the ferromagnetic rod within the helix greatly increases the strength of the magnetic field.

## Summary

A solenoid consists of a wire wrapped in a helix. When electric current is passed through the wire, the solenoid acts like an electromagnet.

Since it is hollow, a solenoid can draw an iron or ferromagnetic rod into the helix. This effect is handy in creating switching or locking devices. By permanently placing an iron rod inside the solenoid creates an electromagnet.

Study the best

## Resources and references

The following are resources on this subject.

### Websites

Solenoid - Hyperphysics

Solenoid - Wikipedia

Magnetism Resources

### Books

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electromagnetic_solenoids.htm

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