Magnetism Basic 5 Basic Science Lesson Note

Learning Objectives: By the end of the lesson, pupils should be able to:

• State the properties of magnets
• Group materials into magnetic and non-magnetic
• Write common applications of magnetism
• Make and use magnets

What is Magnetism?

Magnetism is the invisible force that attracts certain materials, especially iron and steel. This force comes from magnets, which are objects that can attract or repel other magnetic materials.

Magnet is any object that produces a magnetic field and attracts iron, steel, nickel, and cobalt.

Properties of Magnets:

1. Attraction and Repulsion:

• Like poles repel – North pole repels north pole, south pole repels south pole
• Unlike poles attract – North pole attracts south pole
• Attraction is stronger than repulsion – Magnets pull magnetic materials more strongly than they push

2. Magnetic Poles:

• Every magnet has two poles – North (N) and South (S) poles
• Poles cannot be separated – If you break a magnet, each piece still has both poles
• Magnetic field is strongest at the poles – Most attraction happens at the ends

3. Magnetic Field:

• Invisible force field surrounds every magnet
• Magnetic field lines flow from north pole to south pole
• Field is strongest near the poles and weakest in the middle
• Magnetic field can pass through non-magnetic materials

4. Directive Property:

• Free-hanging magnet always points north-south direction
• North pole points toward Earth’s magnetic north
• This property is used in compasses for navigation

5. Induction Property:

• Temporary magnetism – Magnets can make iron objects temporarily magnetic
• Magnetic materials become magnetic when near a strong magnet
• Induced magnetism disappears when the magnet is removed

6. Retention of Magnetism:

• Permanent magnets keep their magnetism for long periods
• Temporary magnets lose magnetism quickly
• Magnetism can be lost through heating, hammering, or dropping

Classification of Materials:

MAGNETIC MATERIALS (Attracted to magnets):

Ferromagnetic Materials:

• Iron – Most common magnetic material
• Steel – Iron mixed with carbon
• Nickel – Shiny metal used in coins
• Cobalt – Hard, shiny metal

Common Magnetic Objects:

• Nails and screws (iron/steel)
• Paper clips (steel wire)
• Scissors (steel blades)
• Keys (often contain iron)
• Coins (some contain nickel)
• Tin cans (steel with tin coating)
• Safety pins (steel wire)

NON-MAGNETIC MATERIALS (Not attracted to magnets):

Common Non-Magnetic Materials:

• Wood – Pencils, tables, chairs

• Plastic – Bottles, toys, rulers

• Glass – Windows, bottles, mirrors

• Rubber – Erasers, balls, tires
• Paper – Books, notebooks, cardboard
• Cloth – Cotton, wool, synthetic fabrics

• Aluminum – Foil, cans, cooking pots
• Copper – Wires, pipes (when not mixed with iron)
• Brass – Musical instruments, door handles
• Stainless steel – Some types are non-magnetic

Common Applications of Magnetism:

Navigation and Direction:

• Compass – Shows direction using Earth’s magnetic field
• GPS systems – Use magnetic sensors for accurate positioning
• Marine navigation – Ships use magnetic compasses
• Aircraft navigation – Planes use magnetic instruments

Industrial Applications:

• Electric motors – Use magnets to create rotation
• Generators – Use magnets to produce electricity
• Speakers and headphones – Magnets convert electrical signals to sound
• Magnetic separators – Separate iron from other materials in recycling
• Lifting magnets – Move heavy iron and steel objects in factories

Medical Applications:

• MRI machines – Use strong magnets to see inside the body
• Magnetic therapy – Some people believe magnets help with pain
• Medical instruments – Some surgical tools use magnets

Household Applications:

• Refrigerator magnets – Hold papers and photos on fridges
• Magnetic latches – Keep cabinet doors closed
• Magnetic knife holders – Store kitchen knives safely
• Toys – Magnetic building blocks, puzzles, games
• Door bells – Electric doorbells use electromagnets

Transportation:

• Maglev trains – Float above tracks using magnetic levitation
• Electric vehicles – Motors use permanent magnets
• Automatic doors – Magnetic sensors detect when people approach

Technology Applications:

• Computer hard drives – Store information using magnetic fields
• Credit cards – Magnetic strips store account information
• Security systems – Magnetic sensors in alarm systems
• Televisions – Older CRT TVs use magnets to control electron beams

Making Magnets:

Method 1: Stroking Method

1. Materials needed: Steel needle or nail, permanent magnet
2. Process:
   1. Hold the steel object (needle/nail)
   2. Stroke it with one pole of the magnet
   3. Always stroke in the same direction
   4. Repeat 30-50 times
   5. The stroked object becomes magnetized

Method 2: Induction Method

1. Materials needed: Iron nail, strong permanent magnet
2. Process:
   1. Place iron nail near (touching) strong magnet
   2. Leave for several minutes or hours
   3. The nail becomes temporarily magnetized
   4. Remove magnet – nail may retain some magnetism

Method 3: Electrical Method (Electromagnet)

1. Materials needed: Iron nail, insulated copper wire, battery
2. Process:
   1. Wrap insulated wire around iron nail (50-100 turns)
   2. Connect wire ends to battery terminals
   3. Nail becomes electromagnetic when current flows
   4. Magnetism stops when battery is disconnected

Method 4: Hammering Method

1. Materials needed: Steel rod, hammer, magnet
2. Process:
   • Point steel rod toward magnetic north
   • Hit rod gently with hammer while aligned north-south
   • Repeat several times
   • Rod becomes weakly magnetized

Testing and Using Magnets:

Testing for Magnetism:

1. Attraction test – See if object is attracted to known magnet
2. Repulsion test – See if object repels known magnet (only magnets repel)
3. Compass test – See if object affects compass needle
4. Suspension test – Hang object freely to see if it points north-south

Using Magnets Safely:

• Keep away from electronics – Magnets can damage phones, computers
• Store properly – Keep magnets away from each other when not in use
• Handle carefully – Strong magnets can pinch fingers
• Keep from small children – Swallowing magnets is dangerous

Caring for Magnets:

• Store with keepers – Iron pieces across poles to maintain strength
• Avoid dropping – Impact can reduce magnetic strength
• Keep cool – Heat reduces magnetism
• Store opposite poles together – Helps maintain magnetic field

ASSESSMENT QUESTIONS

LESSON 1: MAGNETISM (Multiple Choice Questions)

1. Materials that are attracted to magnets are called: a) Non-magnetic materials b) Magnetic materials c) Insulators d) Conductors
2. Every magnet has: a) One pole b) Two poles (North and South) c) Three poles d) No poles
3. Like magnetic poles: a) Attract each other b) Repel each other c) Have no effect on each other d) Stick together
4. Which material is magnetic? a) Wood b) Plastic c) Iron d) Glass
5. A compass works because: a) It has a battery b) It uses electricity c) It has a magnetic needle that points north d) It is made of plastic