Magnets: Uses of magnets – from the everyday to the industries.

People use magnets to keep notes on refrigerator doors. They are an essential part of technology items such as speakers, motors and computer hard disks. Credit cards carry account information on a magnetic strip. Here are some short descriptions on how they care used:

Door Latch

Magnets are a simple, reliable way to latch doors on refrigerators and cabinets.

Speakers

From tiny ear buds to stadium PA systems, every speaker has a magnet in it. The stronger the magnet, the better the sound quality.

Toys and Games

Many familiar toys such as the Woolly Willy drawing game use magnets. Some construction toys use magnets to securely attach parts.

Motors

DC motors have a set of permanent magnets and electromagnets inside. When connected to a battery, the electromagnets repel the permanent magnets and make the motor spin.

Refrigerator Magnets

Refrigerator magnets are used for everything from notes to jokes to the pediatrician's phone number.

Credit Cards

Credit cards have a strip of magnetic material on their backs. Account data are recorded on it in a special, machine-readable format.

Transportation

Magnets are now used in the very advanced technology of public mass transportation known as the Maglev (from the words magnetic levitation) train. Watch the video clip to see how the magnetic system works.

Magnets: Magnetic materials - let's find out!

How to conduct an experiment that aims to find out which materials can be attracted to a magnet.

Magnets: How do magnets behave when placed near each other?

Around a typical bar magnet - or any magnetised object (like the Earth, for example) - there are lines of magnetic flux. These are said to flow away from the north pole and re-enter at the south pole.

These field lines become evident if iron filings are sprinkled over a sheet of paper underneath which there is a bar magnet. Their direction can be plotted using a small 'plotting compass'. The needle aligns with the N-S field (flux) lines and the needle follows the same pattern as revealed by the iron filings.

When two magnets are brought close to each other, the flux lines from both magnets interact. If these flux lines are flowing in the same direction, they will link up and the magnets will attract each other. If they are flowing in opposite directions, they will produce a repulsive force and push away from each other, (often taking the magnets with them!) The force between them depends on the separation distance and the flux density (magnetic strength) of the magnets used

Magnets: How do magnets behave when allowed to move freely?

A magnet can be allowed to move freely. This is usually done by suspending it on a thin thread or floating on water and allowed to rotate and swing freely. The magnet will then interact and align itself to the Earth's magnetic field. However, this is provided that there are no other magnetic or electromagnetic influences.

Magnets: How to make a magnet using the stroking method?

Magnetic materials can be magnetized by stroking. When existing magnet is moved from one end of the item to the other repeatedly in the same direction, the magnetic object becomes a temporary magnet.

Magnets: How to make an electromagnet?

An electromagnet in its simplest form, is a wire that has been coiled into one or more loops, known as a solenoid. When electric current flows through the wire, a magnetic field is generated. It is concentrated near (and especially inside) the coil, and the magnetic field lines are very similar to those of a magnet. The strength of the magnetic field of the electromagnet are proportional to the number of loops of wire. That means, the more loops there are, the stronger the magnetic field. In addition, if it is wrapped around a magnetic material, such as an iron nail, then the overall result may be several hundred to thousand times increase in the field strength.

Magnets: Magnetic fields

Magnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges.

Magnets: magnetism

The term magnetism is used to describe how materials respond to a magnetic field; to categorize of if a material is magnetic. Magnetic materials, like iron and steel are also known as ferrous materials. Materials that are not affected by magnetic fields are known as non-magnetic or non-ferrous materials. They include copper, aluminium, water, gases, and plastic.

Magnets: Magnets

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for properties of a magnet: a force that pushes/repels or pulls/attracts on other magnetic materials like iron and/or other magnets.

A permanent magnet is an object made from a material that is magnetized and creates its own magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are described as magnetic, ferrous, ferromagnetic and ferrimagnetic. These include iron, nickel, cobalt, some rare earth metals and some of their alloys and some naturally occurring minerals such as lodestone.

Some ferromagnetic materials can be magnetized by a magnetic field but do not tend to remain magnetized when the field is removed, they are described as soft. Permanent magnets are made from ferromagnetic materials that stay magnetized and are described as hard.

An electromagnet is made from a coil of wire which acts as a magnet when an electric current passes through it, but stops being a magnet when the current stops. Often an electromagnet is wrapped around a core of ferromagnetic material like steel, which enhances the magnetic field produced by the coil.