Magnestism

Magnetism is the force exerted by magnets when they attract or repel each other. Magnetism is caused by the motion of electric charges.

As you know, every substance is made up of atoms and inside every atom there are electrons which carry electric charges circling the nucleus. Their movement generates an electric current and causes each electron to act like a microscopic magnet.

In most substances, equal numbers of electrons spin in opposite directions, which cancels out their magnetism. That is why materials such as cloth or paper are said to be weakly magnetic. In substances such as iron, cobalt, and nickel, most of the electrons spin in the same direction. This makes the atoms in these substances strongly magnetic, but magnets.

Magnetic materials are always attracted towards a magnet. However, a magnet may be attracted to or repelled from another magnet. 

All magnets have north pole and a south pole. If freely suspended, one pole will point toward the north. The two poles are therefore named the north magnetic pole and the south magnetic pole, or more properly, north-seeking and south-seeking poles, for the attractions in those directions.

Activity 1

You will need:

A bar magnet

a piece of paper

a piece of string

A tub of paperclips or drawing pins

What you will do:

1. Fold the piece of paper so the magnet will sit inside

2. Tie the string to the paper and place the magnet in the paper like the diagram below

3. Hold the string or hang it from a tabletop

4. Leave it hanging until it stops moving

You have made a compass! When it stops moving, the magnet will point roughly North - South.   

Image: Openstax (CC BY)

The Earth acts like a large bar magnet with its south-seeking pole near the geographic North Pole. That is why the north pole of your compass is attracted toward the geographic north pole of the Earth. The magnetic pole that is near the geographic North Pole is actually a south magnetic pole! 

Confusion arises because the geographic term “North Pole” has come to be used (incorrectly) for the magnetic pole that is near the North Pole. The “North magnetic pole” has been given the wrong name; it should be called the South magnetic pole.

5. Hold the north pole of the magnet close to the north pole of the hanging magnet. What happens?

6. Hold the south pole close to the north pole. What happens?

Bringing a north pole and a north pole together will cause the magnets to push away from each other or repel. They will be pushed in opposite directions. If you bring a north pole and a south pole together, they will attract.

7.  Take a magnet and place it in a tub of paperclips or drawing pins. What happens?

Any metal will be attracted to a metal, but not all metals are magnetic. Some materials are magnetic. For example: iron, steel, cobalt, and nickel. 

Image: Images-of-elements.com (CC BY)

There are rare earth magnets such as neodymium magnets. These magnets are the most powerful permanent magnets produced commercially and are popular because they are very strong and are small.

Lots of metals are not magnetic. For example: copper and aluminium.  

Non-metals such as sand, wood and plastic are not magnetic.

Magnets are used in many different applications:

Magnetic elements on a hard disk help to represent computer data, which is later ‘read’ by the computer to extract information.

Magnets are used inside TVs, sound speakers and radios. The small coil of wire and a magnet inside a speaker transforms the electronic signal to sound vibrations.

Magnets are used inside a generator to transform mechanical energy into electrical energy. In contrast, other kinds of motors use magnets to change electrical energy to mechanical energy.

Electrically charged magnets can help cranes to move large metal pieces.

Magnets are used in filtering machines that separate metallic ores from crushed rocks.

It is also used in food processing industries for separating small metallic pieces from grains etc.

Magnets are used in MRI machines which are used to create an image of the bone structure, organs, and tissues. Even magnets are used to cure cancer.

At home, you use magnets when you stick a paper on the refrigerator in order to remember something. Magnets are also used to keep cupboards closed. 

We often use pocket a compass to find out directions when we are on a trek. The pocket compass uses a magnetic needle to point north.

The dark strip on the back of debit and credit cards is magnetic and is used to store data like computers’ hard drives.

Magnets can help collect all the nails which are scattered on the ground after a repair job.

Infinity Learn. (2018). What are the types of magnets? (Standard YouTube licence)