Part of an electromagnet is called a solenoid.
A solenoid is a coil of wire that has an electric current flowing through it. When an electric current flows through a wire, the electricity creates a magnetic field around the wire. If the wire is wound into a coil, the magnetic field around the coil becomes much stronger.
We can make the magnetic field even stronger by putting a rod of iron or steel into the solenoid. The magnetic field becomes stronger because the metal rod is magnetized by the solenoid.
Like a bar magnet, a solenoid has two poles. The flux lines of the magnetic field link together the north and south poles of the solenoid.
How does a solenoid magnetize an iron rod?
The iron rod is made up of lots of groups of atoms called domains. These domains are miniature magnets, but their magnetism has no power because their poles are pointing in different directions.
When an iron rod comes into a magnetic field around a solenoid, the domains in the rod all line up and point one way.
Then the rod has strong magnetic poles at each end and a magnetic field around it.
When an electric current runs through a solenoid, it has poles just like a bar magnet.
One end is a north pole and the other end is a south pole. If you hold an iron or steel rod near a solenoid, the rod becomes magnetized, and the end of the rod that’s nearest the north pole of the solenoid becomes a south pole. In the same way, the end of a rod held near the south pole of the solenoid will become a north pole.
Unlike poles attract, and so the magnetized rod and the solenoid attract each other.
How to make an Solenoid:
Solenoids at work
Can you think of ways in which a solenoid can be useful?
Solenoids can work as a kind of switch in electric door locks, in pinball machines, and in electric circuit breakers.
Solenoids and magnets
Inside a loudspeaker
