Magnetism

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Welcome to class! 

In today’s class, we will be talking about magnetism. Enjoy the class!

Magnetism

Magnetism is the ability of a material to attract iron and steel. Magnets have this ability more than any other material. A magnet is a material that can attract or pull an object made of iron, e.g. nickel, steel, cobalt, etc. Many years ago, in ancient China, some stone-like objects (black iron ore) was discovered to attract small pieces of iron. This stone-like object is called a Lodestone. The term Lodestone means leading stone’.

Lodestone

Lodestone is a special type of mineral magnetite that occurs naturally as a permanent magnet. It is made up of magnetite (Fe304) with the inclusion of magnetite (Fe2O3). Lodestone is a very special iron oxide simply because it has North and south polarity. In the ancient days, sailors use Lodestones as a magnetic compass for navigation.

Magnetic poles and magnetic fields

• Magnetic pole:

It is a region in the magnet with the strongest magnetic force. A magnet has two poles: the North Pole and the South Pole. These poles are located at the ends of the magnets. Like poles repel/push away from each other while unlike poles attract/pull each other. This is referred to as the law of magnetism.

The North Pole of a magnet is the one that always points in the direction of the earth’s North magnetic pole. The South Pole of a magnet is the one that always points in the direction of the earth’s the South Pole. Magnetic pole forces behave like an electric charge.

• Magnetic field:

It is the region around the magnet in which the magnetic force of the magnet can be felt. Magnetic lines of forces are the lines used to represent the magnetic field and they show the strength of a magnet. The magnetic lines of forces are strongest at the end of the pole and weakest in the middle of its poles. It is believed that magnetic fields move from the North Pole into the south pole of a magnet.

The neutral point is a point in the magnetic field of a bar magnet where the magnetic force is not felt, i.e. zero.

Magnetic fields have many properties, which include:

1. Magnetic field lines try to form closed-loop from pole to pole.
2. The field lines move from the North Pole to the South pole.
3. The field lines never cross one another.

Care of magnet

The need to take care of magnets arise from the fact that a magnet can lose its magnetism if:

1. It is subjected to heat. Some flexible magnets must not be heated to a temperature above 180°C.
2. It is hammered repeatedly; Hammering randomly disorganized the arrangement of its molecules.
3. An alternating current is passed through the coil in which the magnet is placed pointing in the east-west direction.
4. It is abandoned for a very long time. Some temporary magnets will lose their magnetic properties when abandoned for a long period.
5. Exposed to too much moisture.

Generally, one of the most important areas of a magnet is its storage. Magnets are stored and preserved mostly by placing them in a thick, steel container with space between the magnets and the inside walls of the steel container.

How to make a magnet

A magnet can be made by the following methods:

1. Stroking: stroking is done by striking a magnet against a magnetic material, e.g. iron.
2. Induction: Induction is done when a magnetic material is attached to a bar of a magnet for a period.
3. Electrical method: This is done when an electric current is passed through a coil of wire (solenoid) and then the material to be magnetized is placed in the solenoid.

Law of magnetism

A magnet consists of two ends, which are North and South poles.

The law of magnetism states that like poles repel each other while unlike poles attract each other.

 

In our next class, we will be talking about Electrical Energy.  We hope you enjoyed the class.

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