The soft iron bar is placed inside the

solenoid and the current is witched on and

off. On removing and testing the bar, it is

found to be magnetised. The magnetic

strength can be adjusted by changing the

current.

Properties

(i)

These materials retain some

magnetism for long time even if

the external magnetic field is

removed

(ii)

They are difficult to magnetise

but hold the magnetic properties

for long

Polarity of an electromagnet

The polarity of electromagnet created by

electromagnet depends on the direction of

the current flow. If the current flows in

anticlockwise direction, the end of the

magnet is North pole while South pole

occurs when the current flows in clockwise

direction

(iii)

These kinds of magnets are made

from hard ferromagnetic

materials

Most permanent magnets used

are artificial

(iv)

(v)

They are alloy (combinations) of

iron, nickel and cobalt.

Applications of temporary magnets

Examples;

(i)

In rail road trucks

In electric motors

In MRI machines

In Microphones

In televisions and computer hard

ware

Alnico (alloy made of

aluminium, nickel and cobalt)

Bar magnet

Lodestone

Ticona

(ii)

(iii)

(iv)

(v)

(ii)

(iii)

(iv)

(v)

Ceramic like materials, made

from a mixture of iron oxide with

nickel, strontium or cobalt

(ferrites) that becomes

magnetised when placed in

magnetic field

(vi)

In cranes

Advantage of electromagnets

The electromagnets are mostly used in many

applications due to the following reasons

Note: These may be naturally occurring

“rare earth” element or chemical compounds

(i)

(ii)

It can be switched on and off

The strength can be controlled by

changing the current

It allows quick loading and

unloading

Steel is called a “hard” material because it is

harder to magnetise and also does not lose

its magnetism so easily. It is used to make

permanent magnets

(iii)

Disadvantages of electromagnet

The electromagnet requires a continuous

supply of electric energy

Applications

(i) In compasses as magnetic catches to keep

cupboards doors shut

Permanent magnets

(ii) Fridges and freezers have magnetic

strips all around the door to keep the door

completely closed and so keep the cold air

inside

Permanent magnets are those which acquire

magnetism due to an applied external and

retain some magnetism even after the

external magnetic field is removed

(iii) A permanent magnet is placed in the oil

sump tank of car engine so that it collects

any bits of steel that are worn off engines.

(iv) To make computer discs, video tapes,

and recording tape for tape recorders.

Example Iron oxide

(v) In Jewelry example earrings,

neckless to assist them clasped (closed)

(vi) removing iron pieces from the eye

of patient in hospitals

(vii)

A freely suspended magnets

always points in north – south

direction

Properties of magnets

(i)

All magnets have two poles, the

north and south pole

(ii)

(iii)

(iv)

(v)

Magnets exert a force on some

materials and do not on others

Magnets attract ferromagnetic

materials and not others

Magnetic force is an action – at a

distance force

In a bra magnet, more iron

fillings stick at the poles,

meaning that the magnetic force

is strongest near the poles of a

magnet, and that the poles have

equal strength

(vi)

When two magnets are brought

together unlike poles attract each

other while like poles repel each

other

Note that: the North pole of a freely

suspended magnet points in the north

direction, and the south pole points in

the south direction of the earth.

The end pointing North is called North –

seeking pole (N – pole) of the magnet.

The other side is the South – seeking

pole (S – pole) of the magnet.

SHAPES OF MAGNETS

Magnets have different shapes as

mentioned below

(i)

Horse shoe magnet

Bar magnet

Ring magnet

(ii)

(iii)

(iv)

Ball ended magnet

(v)

(vi)

(vii)

Cylindrical magnet

Disc magnet

Magnetic needle

➢ Magnadular magnets consists

basically iron oxide and barium

oxide

(viii) Ceramic (magnadular) magnet

The figures on the diagram below shows

some of the shapes of the magnets

Applications of magnets

Magnets are widely used in various

electronic devices, as described below.

(i)

In magnetic recording media

Magnetic recording is a

technology that stores

information on a magnetic

medium. Example computer hard

disks

(ii)

In credit, debit ATM cards

The ATM cards have magnetic

strips on one of their sides which

have necessary information of

the customer’s account

(iii)

In CRT (cathode ray tube)

television and computers

These uses an electromagnet in

their inputs to assist in producing

an image on the screen

Ceramic (Magnadular) magnets

(iv)

(v)

In electric generators

These use permanent magnets to

convert mechanical energy to

electrical energy

➢ Ceramic magnets have its pole

on its faces while other magnets

have their poles at the opposite

ends

In electromagnets

Electromagnets are used in

hospitals when dealing with eye

injuries caused by iron or steel

splinters

➢ These magnets are stronger than

other magnets of comparable

sizes

➢ They are greyish/black in colour

Also, are used in magnetic

resonance imaging (MRI) to

diagnose brain tumors,

hemorrhage, nerve injuries and

stroke injury

Answers

The objects that could be attracted by a

magnet are the nail and the paper clips

Their characteristics are:

Electromagnets are also used in

steelworks and cranes

(i)

They are made of iron or steel

They can be magnetised

They are metallic

(ii)

(iii)

(iv)

They are attracted to the magnet

(vi)

In speakers and microphones

These use permanent magnets

and current – carrying coils to

convert electrical energy to

sound energy

(c) which objects could not be attracted by a

magnet? Why?

Answers

The objects that could not be attracted by the

magnets are plastic ruler, coin (if not iron),

and wooden pencil.

(vii)

In moving coil meters

A horse shoe electromagnet is

used in voltmeters and ammeters.

It is an inbuilt part of these

devices that enables the pointers

to move in a direction of

They are not attracted because, are non –

magnetic materials

increasing voltage or current

Example 02

Example 01

A student argues that all matters are

magnetic. Do you agree or disagree?

Explain your answer with examples.

In a certain primary school, a teacher

demonstrated how magnets work by giving

students different objects like nail, plastic

ruler, coin, wooden pencil, and paperclip,

along with a bar magnet. The students were

asked to identify objects that were attracted

to the magnet and those which are not.

Answers

I disagree with the statement that all

matter is magnetic in everyday sense of

magnetism.

All matter is made of atoms, and atoms

contain electrons that produce magnetic

effects. However not all materials show

noticeable magnetism. Materials can be

classified as

(a) Why could some objects be attracted to

the magnet and others not?

Answers

Magnetic materials (ferromagnetic): -

these are strongly attracted to the

magnets and can be magnetised

permanently and easily show

magnetism, example iron, cobalt, nickel

and steel

Some objects were attracted to the magnet

because they are made of magnetic materials

such as iron or steel. Other objects were not

attracted because they are made of non-

magnetic materials like plastic, wood or

rubber, which do not respond to magnets.

Weakly magnetic materials: - these

respond very weak to magnetic fields

and their magnetic field is usually not

(b) Which of the objects could be attracted

by a magnet? What are their characteristics?

noticeable, example aluminium, copper

and glass.

Method of operation:

1. The magnet is brought close to or passed

over the mixed waste

Non – magnetic materials: - these show

no observable magnetic effect under

normal conditions, examples paper,

rubber and water

2. magnetic materials (iron rods and nails)

are attracted to the magnet and stick to it

3. Non – magnetic materials (plastic

wrappers, glass pieces, and paper) are not

attracted and remain behind

Example 03

Explain the concepts of paramagnetic and

permanent magnet as discussed in

magnetism.

4. The magnet is then moved to a separate

container and the magnetic materials are

removed (or the electromagnet is switched

off so they fall).

Answers

This method works because iron and steel

are ferromagnetic, while plastic, glass, and

paper are non – magnetic. It provides a

simple and effective way to separate

magnetic materials from wastes.

(i)

Paramagnetic are materials that

can be temporarily magnetised.

Example, aluminium and

chromium

Permanent magnet is a

magnetised material which retain

its magnetism for a very long

period of time

(ii)

Example 05

State three applications of magnets

Answers

Example 04

You are asked to design a simple tool for

separating magnetic materials from a pile of

mixed waste at a recycling centre. The pile

contains nails, plastic wrappers, glass pieces,

iron rods, and paper. Describe the tool you

would design and the method by which it

operates.

(i)

In moving coil metres such as

voltimeter and ammeters

(ii)

(iii)

In speakers and microphones

In credit, debit and ATM cards

Answers

Example 06

Tool to be designed:

(a) Describe the experiment to demonstrate

the differences in the magnetic properties of

iron and steel and state the conclusion to be

derived from it?

A magnetic separator using a strong

magnet (electromagnet or permanent

magnet).

Answers

The too consists of a strong magnet

mounted on a handle or placed above a

moving belt or tray. It is positioned over

the pile of mixed waste at the recycling

centre

Wind equal number of turns of insulated

wire around the iron rod and the steel rod

separately to form two electromagnets then

connect each coil to the same battery (one at

a time).

Bring iron fillings or paper near each rod

and observe how many are attracted. Switch

the current and again observe whether the

rod still attract fillings.

Example 07

You are given a small plotting compass and

three grey metal bars. One aluminium, one

is Iron, one is a magnet. How can you

identify them?

Observations

When current is turned ON: iron attracts

more iron fillings than steel

Answer

By using the plotting compass on each bar

When current is turned OFF: iron loses

magnetism quickly but steel retains

magnetism and continuous to attract some

fillings

The compass is brought close to each bar

especially near the ends.

Magnet: The compass needle strongly

deflects.

Conclusion:

One end of the bar attracts the north end of

the compass needle and other end attracts

the south end. This shows that the bar has

fixed poles and is a magnet

Iron is easily magnetised and easily

demagnetized (soft magnetic material)

Steel is harder to magnetise but retains

magnetism for a long time (hard magnetic

materials)

Iron bar: The compass needle is attracted to

both ends of the bar.

There is no clear north or south pole. This

happens because iron magnetised

temporarily by the magnetism of the

compass. This proves it is Iron

(b) Which of these metals would you use for

(i) the core of electromagnet

(ii) a compass needle, and

Aluminium bar: The compass needle shows

little or no deflection.

(iii) magnetic screening/ Give reason for

your answer

This is because, aluminium is non –

magnetic material. This prove it is

aluminium.

Answers

(i) Iron, because iron magnetizes strongly

when current flows. It loses magnetism

quickly when current is switched off. This

allows the magnetism to be switched ON

and OFF easily.

Example 08

Explain the following.

(a) Magnets are often fitted to the doors of

refrigerator and cupboards.

Answers

(ii) Stell, because steel retains magnetism

for a long time. A compass needle must be

permanently magnetised

To keep the doors securely closed

The magnet in the door attracts the metal

frame of the refrigerator or cupboard,

pulling the door shut. This prevents the

accidental opening of the door due to

gravity, air movement or small vibrations.

(iii) Iron, because has high magnetic

permeability. It attracts and redirects

magnetic field lines, reducing the magnetic

field inside the protected regions

(b) A crane in a steelwork fitted with a large

electromagnet

Answers

Because the magnetic force holds the screw

onto the tip of the screwdriver.

So, that it can lift, move and release heavy

iron or steel objects easily and safely.

The magnetic attraction keeps the screw

firmly attached, even if the screwdriver is

tilted or upside down. This makes the crew

placement easier and more accurate.

A steelwork crane uses a large

electromagnet because it provides a

powerful, controllable, and safe way to

handle heavy steel and iron materials

efficiently

Example 09

(c) Flour is usually passed near a magnet

before being packed

In which part of a fridge or a microwave

oven do magnetic strips installed? Why?

Answers

Magnets help to remove small pieces of iron

or steel that may have accidentally mixed

with the flour during processing.

Refrigirator (fridge): It placed inside the

rubber door gasket (door seal) around the

edge of the fridge door

This protects the consumers by removing

dangerous metal impurities from flour

Reason: The magnetic strip pulls the door

tightly closed against the metal body of the

fridge. This creates the right seal, which

prevents cold air from escaping and keeps

warm air from entering

(d) A steel ship becomes magnetised as it is

constructed

Answers

Microwave Oven: it is placed around the

edge of the microwave door (inside the door

frame)

This is because of the presence of the earths

magnetic field and construction process like

hammering and welding which aligns the

magnetic domain in one direction since steel

is a ferromagnetic material.

Reason: The magnetic strip helps ensure the

door closes firmly and aligns correctly. This

is important to prevent microwave radiation

leakage and maintain safety during

operation

Because of this, ships are often degaussed

(demagnetized) using electric cables and

currents to reduce their magnetism

In some designs, magnets also help activate

safety interlocking switches, ensuring the

microwave works only when the door is

fully closed

(e) The sump plug on a car is usually

magnetised

Answers

The sump plug (oil drain plug) on a car is

usually magnetised to protect the engine.

Example 10

A magnetised sump plugs acts like a filter

for metal debris, helping protect the engine

and external life.

Choose material, giving a reason for each of

the following:

(a) the core of an electromagnet

(b) a compass needle

(f) A magnetised screw driver can help to

place screw in holes that are hard to reach

Answers

(c) the case of a compass

The magnetic poles are the two ends of a

magnet or magnetised body where the

lines of forces are most concentrated

Answer

(a) Soft iron

Note: The experiments show that, the

iron fillings tend to cling near the ends

of the bar magnet. This shows that, the

attraction force is stronger at the poles

than other parts of the magnets.

Reason: Because soft iron is a ferromagnetic

material with high magnetic permeability, so

it becomes strongly magnetized when

electric current flows through the coil. It

also has low retentivity, meaning it loses its

magnetism quickly when the current is

switched off.

This makes soft iron ideal for electromagnet

because the magnets can be easily turned on

and off and produces a strong magnetic field

when in use

Magnetic axis and meridian

Magnetic axis: is a straight-line drawn

passing through the magnetic dipoles

(b) Steel

Reason: A compass needle must be

permanent magnet so that it can align itself

with the Earth’s magnetic field.

Steel suitable because, it is ferromagnetic

and can retain magnetism for along time.

This allows the needle to consistently point

in the north – soft direction, making the

compass reliable.

Magnetic Meridian: is a vertical plane

which the magnet comes to rest with its

axis lying in the magnetic north – south

direction

(c) Plastic (sometimes brass or aluminium)

Reason: The case must be non – magnetic

material so that it does not affect the

magnetic field or disturb the needle because

the compass works using a magnetic needle.

Plastic is non – magnetic and does not

interfere with the compass needle.

Magnetic poles

Magnetic pole is a place in a magnet

where the resultant attractive force

appears to be concentrated.

Breaking a magnet