Electromagnetism

 

Electromagnets

When a wire has an electric current running through it, it makes a magnetic field. This can be used to make an electromagnet. The picture below shows a simple way to make an electromagnet, by wrapping a coil of wire around a nail made of iron.

 

 

Electromagnet

An electromagnet is a kind of magnet that only works when there is electricity. The word electromagnet has two parts. ‘Electro’ means electricity and ‘magnet’ means magnetism. When a coil of wire has an electric current going through it, it makes a magnetic field. The coil becomes an electromagnet. The magnetic field goes away when the current stops.

 

 

Electromagnetism

A wire that has current going through it makes a magnetic field. But most of the time, the magnetic field is too weak to matter or to have a noticeable effect.

The magnetic field around a wire with current is circular. The field is stronger near the wire, where the field lines are closer together.

 

 

Any wire with current flowing through it has a magnetic field.

A coil of wire with several turns is called a solenoid. The coil of wire makes a magnetic field when there is current flowing through it. The magnetic field is similar to the one that a bar magnet has:

 

 

A coil carrying electric current and a bar magnet have similar magnetic fields.

 

In the example above, the coil of wire produces a magnetic field that flows out from the north to the south pole. The two open ends of the coil are attached to a power supply. When you turn the power on and current is flowing through the wire, it will produce a magnetic field. When you turn the power off, the electromagnet loses its magnetism. This makes it useful for scrap yard crane drivers as they are able to switch the electromagnet on and off to pick up and drop magnetic materials. You can also find electromagnets used in automatic door locks, headphones, and even levitating trains.

Electromagnets can also be made stronger or weaker.

 

Making electromagnets stronger

There are essentially three main ways to increase the strength of an electromagnet:

 

• Wrapping the coil around an iron core.
• Increasing the current flowing through the coil.
• Increasing the number of turns of the coil.

 

 

Wrapping the coil around an iron core.

Adding a soft iron core will increase the strength of an electromagnet.

 

 

Increasing the current flowing through the coil.

Increasing the current through the wire will produce a stronger magnetic field (see image below).

 

 

Increasing the number of turns of the coil.

 

Using more turns on the coil of wire will produce a stronger magnetic field (see image below).

 

Summary:

 

• A magnetic field is produced by an electromagnet when it has an electric current flowing through it.
• An electromagnet can be made stronger by doing any of these three things:
• making the current larger
• wrapping more coils of wire around it
• putting an iron core inside it
• An electromagnet that also has a permanent magnet can be useful for making things like motors and loudspeakers.