Fun with Magnets - Class 6 Notes & Olympiad Questions

Fun with Magnets

a) Magnets are special objects that have the ability to attract certain materials like iron, cobalt, and nickel. Magnets have a force called magnetism or magnetic force that pulls those objects towards them.
b) There are different types of magnets. Some magnets occur naturally, like a special rock called magnetite. Others are made by people and are called artificial magnets. These artificial magnets can be temporary or permanent.

Types of Magnets

Temporary Magnets

Temporary magnets are ones that you can turn on and off. For example, if you rub a piece of iron or steel with a magnet, it can become temporarily magnetic. But if you remove the magnet, it will lose its magnetic power.

Permanent Magnets

Permanent magnets, on the other hand, always have their magnetism. You can't turn it off. These are the kind of magnets you commonly see in everyday objects like refrigerator magnets or the magnets in speakers.

Magnetic and Non-magnetic Material

There are two types of materials when it comes to magnets: magnetic materials and non-magnetic materials.

Magnetic Materials

a) Magnetic materials are the ones that get attracted towards magnets. They are strongly influenced by magnetism.
b) Some examples of magnetic materials are iron, nickel, and cobalt. When you bring a magnet close to these materials, they feel a pull and can stick to the magnet.

Non-magnetic Materials

a) Non-magnetic materials are the ones that do not get attracted to magnets. They are not affected by magnetism.
b) Some examples of non-magnetic materials are leather, cloth, paper, and wood. When you bring a magnet close to these materials, nothing happens. They don't stick or get pulled towards the magnet.

Poles of a Magnet

a) Every magnet has two ends or poles: the North Pole and the South Pole.
b) These poles are opposite to each other.
c) The force of attraction between a magnet and a magnetic material is strongest at these two poles. So, if you bring a magnet close to a magnetic material, the material will be most strongly attracted to the North or South pole of the magnet.

Properties of Magnet

1. Like poles attract, and unlike poles repel: This means that if you bring two magnets close together and their same poles (both North or both South) are facing each other, they will push away or repel each other. However, if their opposite poles (one North and one South) are facing each other, they will attract and pull together.

2. Repulsion is a reliable indicator of magnetism: To check if an object is a magnet or not, you can try to bring another magnet close to it. If they repel each other, it means the object is magnetic.

3. A freely suspended magnet points North-South: If you hang a magnet freely (for example, by a string), it will align itself in a specific way. One end of the magnet will point towards the North, and the other end will point towards the South. This property helps us determine directions using a magnet.

4. Broken magnets act as individual magnets: If you break a magnet into smaller pieces, each piece will behave as an individual magnet with its own North and South poles. This property is why magnets can be cut into different shapes and sizes.

5. Magnets can lose their magnetism: Certain actions can cause a magnet to lose its magnetic properties. Dropping a magnet, heating it to a high temperature, or subjecting it to strong impact (hammering) can demagnetise it.

6. Magnets can have an effect through some materials: Magnets have the ability to attract or repel objects without direct contact. The magnetic effect can pass through certain materials like cloth, plastic, glass, and even air.

Earth’s Magnetic Field

a) The Earth has a special feature called its magnetic field. It's like a big invisible shield that surrounds our planet. This magnetic field is created by the movement of molten iron and nickel deep inside the Earth's outer core.
b) We can think of the Earth's magnetic field as if there's a giant bar magnet inside the planet. This bar magnet has its North and South poles, just like a regular magnet.
c) The Earth's magnetic poles are not exactly in the same place as the geographic poles that we see on maps.
d) The Earth's South magnetic pole is located near the geographic North pole, and the Earth's North magnetic pole is located near the geographic South Pole.
e) Because of this, when we hang a magnet freely, its North pole points towards the geographic North pole (which is actually the Earth's magnetic South pole). Likewise, the South pole of the magnet points towards the geographic South pole (which is actually the Earth's magnetic North pole).

Methods of Making a Magnet

There are several methods for making a magnet. Three common methods are:

Single Touch Method

a) In this method, you take a piece of iron that you want to turn into a magnet. Then, you stroke it with one pole of a bar magnet in only one direction.
b) You repeat this process around 40-50 times.
c) The end where you start the stroking becomes the same polarity as the pole of the bar magnet used, while the other end becomes the opposite polarity.

Double Touch Method

a) In this method, you use two magnets of equal strength. You take a piece of iron and place it between the opposite poles of the two magnets, in the middle.
b) Then, you stroke one magnet on the iron piece in a clockwise direction, while simultaneously stroking the other magnet in an anti-clockwise direction.
c) After reaching the ends, you lift the magnets and bring them back to the middle position.
d) This process is repeated about 30 times.
e) As a result, the ends of the iron piece acquire the opposite polarity of the magnets used for stroking.

Using Electricity

a) Another method to make a magnet is by using electricity. You can take a piece of iron and wrap a wire around it.
b) When an electric current flows through the wire, it creates a magnetic field around the iron. This turns the iron into an electromagnet.
c) As long as the electric current flows through the wire, the electromagnet exhibits magnetic properties. However, if the electric current is turned off, the magnetism disappears.
d) That’s why electromagnets are temporary magnets.

Storing a Magnet

Magnets should be stored properly to prevent them from becoming weak over time.

Bar Magnets

a) It's best to store the bar magnets in pairs.
b) Make sure that the unlike poles (North and South) are on the same side of each pair. This helps to maintain their magnetic strength.
c) In addition, place a non-magnetic material (such as wood or plastic) between the pairs of bar magnets.
d) You can also use two pieces of soft iron, called magnetic keepers, to sandwich the pairs of bar magnets together. This arrangement helps to redirect the magnetic field and preserve the magnetism.

U-Shaped (Horseshoe) Magnets

a) For U-shaped magnets, generally, only one magnetic keeper is needed.
b) This keeper is placed across the open ends of the magnet, connecting the poles together.
c) The keeper helps to complete the magnetic circuit and preserve the magnetism.