Lesson Notes By Weeks and Term - Junior Secondary School 3

TERM: FIRST TERM

SUBJECT: BASIC SCIENCE

CLASS: JSS 3

REFRENCES

• BasicScience Made Easy for JSS Three by F.I Kehinde et al
• BasicScience Made Easy for JSS Two by F.I Kehinde et al
• STAN Integrated Science for JSS Three
• Precious Seeds Basic Science for JSS three by J.O Otugboyegaet al.

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WEEK TEN

TOPIC: MAGNETISM

CONTENT

• Introduction.
• Law of magnetism.
• Magnetic poles and field.
• Care of magnet.

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A magnet is a substance or materal that attracts metals like iron and other ferometals. Magnetism is the ability of a substance to attract a metal that contains iron.

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LODESTONE

Lodestones are rock that are magnetic. They are made of magnetite (Fe3O4) a form of iron oxide. A piece if iron is then referred to as a lodestone. The Chinese appear to have been the first to discover the lodestone. These qualities of lodestone led to its use as an early form of compass by Chinese sailors. This is because when the stone is magnetized it will be attracted to the earth's magnetic field pole. Also, when it is suspended in the air it slowly turns and points towards the pole.

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LAWS OF MAGNETISM

When a bar magnet is suspended so that it can freely rotate and then freely come to rest. It is noticed that it remains in a North-South direction. Also, when the pole of another bar magnet is brought near the north pole of the suspended bar magnet, the magnet would not attract each other, that is, they repel. But when the north pole of the bar magnet is brought towards the south pole of the suspended bar magnet, they would attract each other.

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Therefore, in each case, when like poles are brought near each other there is repulsion. When unlike poles are near each other there is attraction. These led to the laws of magnetism which states that:

"Like poles repel each other while unlike poles attract each other". E.g. north-north or south-south will repel while south-north or north-south will attract.

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MAGNETIC POLE AND MAGNETIC FIELD

To identity magnetic poles, a magnet can be brought near a magnet whose poles have already been Identified (a standard magnet). If attraction occurs, it means that the pole of the magnet beside the identified pole of the standard magnet is not alike e.g. North pole of the standard magnet will be� attracted to the south pole of the other magnet and vice versa. If repulsion occurs, it means both poles are alike and by this the unknown poles of the magnet are consequently identified.

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EVALUATION

1. What is magnetism?
2. State the law of magnetism.

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MAGNETIC FIELD

This is a condition found in the region around a magnet, characterized by the existence of magnetic poles. It can also be described as the region or space around a magnet in which magnetic force is felt.

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THE CARE OF MAGNETS

There is the need to care for magnets so that they would not lose their ability to magnetise. The following ways are necessary for caring for magnets.

1. Magnets should be heaped with like-magnets. They should be kept away from the edge of flexible magnets because it can actually reverse the polarity.
2. Replacement covers can be purchased for many of the polar power magnets because magnet covers and materials may eventually be worn and torn
3. They should be clean by wiping them gently with a damp soapy sponge and should not be immersed in water.
4. They should be stored by spreading magnetic signs flay on a smooth metal surface.
5. They should not be left in hot weather or brought close to fire as it can destroy their properties.

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GENERAL EVALUATION

1. What is magnetic field?
2. Give three cares of magnet
3. Mention five effect of flooding
4. Mention three positive uses of the internet.

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READING ASSIGNMENT

Precious Seeds Basic Science for JSS three by J.O otugboyega et al. chapter 21 Pages 114-116

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WEEKEND ASSIGNMENT

1. Lodestone is a ___� A. Magnetic rock� B. Magnetic plate C. magnetic field D. magnetic ray
2. One of the following is a method of magnetization A. heating B. hammering�

1. induction D none of the above

1. Like poles ____ A. attract B. repel C. join D. contact
2. The following are ways to care or magnet except A. should be kept with other magnets B. should be kept clean C. should be left in hot water D. none of the above
3. The chemical formula or magnetite is A. Fe2O3 B.FeO C. Fe3O D. Fe3O4

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THEORY

1. What is a magnetic field?
2. List three ways in which a magnet can be formed.
3. List five ways to care or a magnet.

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