(v)

Do not subject magnets to any

form of severe stress such as

vibrations or mechanical impacts.

These can physically damage the

magnets

Example 04

Give five ways you can make the magnet

stay longer

Answers

(i)

Store away from ferrous

materials

Note:

(i)

(ii)

Store in pairs and using magnetic

keeper

Store away from heat

Store away from strong electric

and magnetic fields

Magnetic field is an indication of

the strength and direction of a

force a magnet exerts on

magnetic materials

If the magnetic field is stationary,

it is referred to as magnetostatic

field

(iii)

(iv)

(ii)

(v)

Store away from strong vibration

(iii)

(iv)

At any point its magnitude and

direction remain the same

(uniform)

Magnetic field can be one of the

important applications as used in

the magnetic inks and paints as

well as magnetic liquid as

explained below

Example 05

How can you store magnets for effective and

durable use of their magnetism?

Answers

1. Store bar magnets in pairs with unlike

poles together and soft iron keeper placed

across the ends

Magnetic inks and paints

2. keep magnets away from heat, and strong

electric current

Magnetic inks are made by mixing very

small particles of magnetic substances with

a liquid. The mixture is made in dark brown

colour

3. Do not repeatedly harmer magnets as this

can demagnetize them

Uses of magnetic inks

Magnetic field of a bar magnet

(i)

To make magnetic tape –

recorders

A magnetic field is the region around a

magnet in which the magnetic force can be

experience by magnetic materials

(ii)

Banks use magnetic ink on

cheques so that the cheques can

be automatically sorted by the

machine which detects the

magnetic field round each

number

(iii)

Automatic cash – cards also use

magnetic ink to store information

helps in fast, clean and efficient

transportation

Magnetic liquids

Magnetic liquid is a mixture of magnetic ink

with oil. The oil prevents it from drying

Magnetic lines of force

Uses of magnetic liquids

Magnetic lines of force are imaginary lines

used to represent a magnetic field

(i)

To detect very small cracks in the

surface of steel pipelines

Are also called magnetic field lines

(ii)

To lubricate the shafts of motors

and coils of loudspeakers

Applications of magnetic field

1. In banking industry

Banks use magnetic on cheques and cheque

deposit slips so that the cheques are stored

automatically by machines.

Purpose (importance) of field lines

Note: These machines can detect the

magnetic field around each number

1. Help us to visualize the shape and

direction of magnetic field

2. In hospital

2. help us to understand how magnets

interact with materials like iron fillings

Hospitals use strong magnetic fields in MRI

(magnetic Resonance Imaging) machines to

scan the inside the human body. The

magnetic field helps create clear images of

organs like the brain and hear without

surgery

3. Help us to predict the motion of magnetic

compass in a magnetic field

Properties of magnetic lines of force

The following are some properties of

magnetic line of force

3. In security

Security checkpoints use magnetic fields in

metal detectors to find weapons or

prohibited metal objects. When metals pass

through the magnetic field, it is detected and

trigger an alarm

(i)

Magnetic lines of force are

continuous and always form a

closed loop

(ii)

Lines of force from the magnet

leaves the north pole and enters

the south pole and back to the

north pole forming a closed loop

Magnetic lines of force are close

together where the magnetic

force is stronger, and they are far

apart where the magnetic force is

weaker

4. In agriculture

(iii)

Magnetic fields are used in electric motors

than run water pump for irrigation. These

pumps help farmers supply water to crops

efficiently

(iv)

(v)

Magnetic lines of force never

cross one another

Parallel magnetic lines of force

in the same direction repel one

another. Parallel magnetic lines

5. In transportation

Magnetic fields are used in electric motors

that power electric trains and cars. This

of force in opposite directions

attract each other

Neutral point in magnetic field

Neutral point is a point where the net

magnetic field is zero

(vi)

Magnetic field lines of forces

pass through magnetic and non-

magnetic materials

(vii)

Magnetic lines of force always

enter or leave a magnetic

material at right angle to the

surface

Formation of neutral point

Neutral point is formed when two bar

magnets are placed near each other with like

poles facing each other

Their magnetic fields repel from each other

such that at one point they completely

cancel each other forming a neutral point.

There is no magnetic force at neutral point

Magnetic field pattern due to a single

(isolated) magnet

Note:

(i)

At any point where two different

magnetic fields exist, a stronger

field is created if they are in the

same direction but a weaker field

arises if they in opposite

directions

(ii)

It is possible for two fields to

balance each other at one point.

At another point where the

magnetic field cancel is a neutral

point

i. Magnetic

materials

A. like poles repel, unlike

poles attract

Magnetic shielding (screening)

ii. Law of

polarity

B. magnetic field is zero

Magnetic shielding is the process of limiting

the flow of magnetic field between two

locations by separating them with a barrier

made of conducting ferromagnetic material

C. redirect magnetic lines

of force

iii. Magnetic

shielding

D. strong magnet

E. iron nail

iv. Neutral

point

F. paramagnetic

G. ferromagnetic

v. Aluminium

vi. Iron

Example 02

Action

State the properties of the magnetic field

lines

Suppose a region is to be shielded from

magnetic effects, it could be enclosed with

ring made up of soft iron. The field lines

could follow the iron ring around the

shielded part

(i)

Run from north pole towards

south pole

(ii)

Are continuous and always form

closed loops

Note:

(iii)

(iv)

Never cross each other

Repel each other if pointing in

the same direction and attract

each other if pointing in opposite

directions

(i)

Field lines from the north pole

cannot be stopped from moving

to the south pole of a magnet, but

then can be redirected

(v)

Pass through magnetic and non –

magnetic material

(ii)

In this case, the channel is a

length of ferromagnetic material

such as soft iron. When the

magnetic field lines reach the

iron, they flow along it rather

than through the magnet itself

(vi)

Always enter or leave a magnetic

material at right angles to the

surface

Example 03

(iii)

The materials that can redirect

the magnetic field lines are said

to be permeable

Describe the process of magnetic shielding

Answers

Magnetic shielding is the process of limiting

the flow of magnetic field between two

locations by separating them with a barrier

made of conducting ferromagnetic material

Example 01

Match each item in List A against its

corresponding item from List B by writing

the correct response in the table provided

List A

List B