Magnetism

1
Chapter 16
Magnetism
Contents 12.1 Materials Magnets 12.2 Magnetic
Induction 12.3 Magnetic Domain Theory of
Magnetism 12.4 Methods of Magnetisation 12.5 Metho
ds of Demagnetisation 12.6 Magnetic
Fields 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
2
Chapter 16
Magnetism
At the end of this chapter you should be able to

• state the properties of magnets

• give an account of induced magnetism

• distinguish between magnetic non-magnetic
  materials

• describe methods of magnetisation

• describe methods of demagnetisation

Magnetism
3
Chapter 16
Magnetism
At the end of this chapter you should be able to

• describe how to use a plotting compass to plot
  magnetic field lines (excluding Earths
  magnetic field)

• distinguish between the magnetic properties of
  iron steel

• distinguish between the design of permanent
  magnets electromagnets

• distinguish between the application of permanent
  magnets electromagnets

Magnetism
4
Unit 12.1
Materials Magnets
Discovery of the phenomenon About 900 years ago,
the Chinese found that a dish carrying a certain
type of rock known as magnetite would constantly
float in water in a North-South direction.
Magnetism
5
Unit 12.1
Materials Magnets

• Magnetic materials
• Magnetite consists of an iron oxide.
• Natural magnet attracts certain materials
• cobalt
• nickel
• iron
• steel
• alloys of any of the above
• These materials are called Magnetic materials.

Magnetism
6
Unit 12.1
Materials Magnets

• Non-Magnetic materials
• Natural magnet cannot attract other materials.
• These include
• copper
• brass
• wood
• plastics
• materials other than iron, steel, cobalt, nickel
• These materials are called Non-Magnetic
  materials.

Magnetism
7
Unit 12.1
Materials Magnets
Properties of magnets All magnets exhibit the
following properties
Magnetism
8
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• Attract magnetic materials

Magnetism
9
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• They have 2 magnetic poles the North and South
  seeking poles. These are the strongest parts of
  the magnets. The poles are found very near (but
  not at) the ends of the magnet.

Magnetism
10
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• If allowed to swing freely a magnet will come to
  rest with one end pointing towards the Earths
  North pole, the other end pointing towards the
  Earths South pole.

Magnetism
11
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• Hence, a magnet can be used as a compass for
  navigational purposes.

Magnetism
12
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• Law of magnetic poles
• Take a look at the following actions taken
  during an experiment. What can you conclude ?

(Step 1)
(Step 2)
Magnetism
13
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• Law of magnetic poles
• Take a look at the following actions taken
  during an experiment. What can you conclude?

Magnetism
14
Unit 12.1
Materials Magnets

• Properties of magnets
• All magnets exhibit the following properties
• Law of magnetic poles
• Conclusion Like poles repel, Unlike poles
  attract.

Magnetism
15
Unit 12.1
Materials Magnets
Properties of magnets Question 1 In an
experiment conducted to test if an object is a
magnet, one end of this object (A) is brought
near one end (X) of a suspended bar
magnet. Attraction occurs. Can you conclude that
the object is a magnet?
Magnetism
16
Unit 12.1
Materials Magnets
Properties of magnets Question 1 In an
experiment conducted to test if an object is a
magnet, one end of this object (A) is brought
near one end (X) of a suspended bar
magnet. Attraction occurs. Can you conclude that
the object (A) is a magnet? Answer Not yet.
The object could have been a magnet with end A
an opposite pole to that of end X of the magnet,
or
Magnetism
17
Unit 12.1
Materials Magnets
Properties of magnets Question 1 In an
experiment conducted to test if an object is a
magnet, one end of this object (A) is brought
near one end (X) of a suspended bar
magnet. Attraction occurs. Can you conclude that
the object is a magnet? Answer Not yet. The
object could have been a magnet with end A an
opposite pole to that of end X of the magnet
or The object could just have been an ordinary
magnetic material (unmagnetised yet).
Magnetism
18
Unit 12.1
Materials Magnets

• Properties of magnets
• Question 2
• In the same experiment,
• The same end of this object (A) is brought near
• the other end (Y) of a suspended bar magnet.
• If attraction occurs again, can you conclude now
  that the object is a magnet?
• If repulsion occurs instead, can you conclude now
  that the object is a magnet?

Magnetism
19
Unit 12.1
Materials Magnets

• Properties of magnets
• Question 2
• In the same experiment,
• The same end of this object (A) is brought near
• the other end (Y) of a suspended bar magnet.
• Answer
• If attraction occurs again, can you conclude now
  that the object is a magnet?
• No, the object is just an unmagnetised
  magnetic material as
• no repulsion between the object bar
  magnet was observed.
• If repulsion occurs instead, can you conclude now
  that the object is a magnet?

Magnetism
20
Unit 12.1
Materials Magnets

• Properties of magnets
• Question 2
• In the same experiment,
• The same end of this object (A) is brought near
• the other end (Y) of a suspended bar magnet.
• Answer
• If attraction occurs again, can you conclude now
  that the object is a magnet?
• No, the object is just an unmagnetised
  magnetic material as
• no repulsion between the object bar
  magnet was observed.
• If repulsion occurs instead, can you conclude now
  that the object is a magnet?
• Yes, it is a magnet.
• Since only like poles repel (A repels Y)
• unlike poles attract (A attracts X),
• the object is indeed a magnet.

Magnetism
21
Unit 12.1
Materials Magnets
Properties of magnets Remember Repulsion is
the only true test for polarity.
Magnetism
22
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction 12.3 Magnetic
Domain Theory of Magnetism 12.4 Methods of
Magnetisation 12.5 Methods of Demagnetisation 12.6
Magnetic Fields 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
23
Unit 12.2
Magnetic Induction
Induced Magnetism

S
N
Far apart



Soft
-
iron bar

Permanent magnet

Magnetism
24
Unit 12.2
Magnetic Induction
Induced Magnetism When a non-magnetised
magnetic material is brought near to (or touches)
a magnet, the material itself will become a weak
magnet. This is called induced magnetism (which
means the material has magnetism induced in it).
Magnetism
25
Unit 12.2
Magnetic Induction
Induced Magnetism Notice that magnetic
induction, an opposite pole is always induced. In
other words, 2 unlike poles facing each other is
observed during magnetic induction.
Magnetism
26
Unit 12.2
Magnetic Induction
Induced Magnetism If placed sufficiently
near to each other, attraction occurs between
the permanent induced magnets.
Magnetism
27
Unit 12.2
Magnetic Induction
Induced Magnetism Induced magnetism in
magnetic materials is the reason that these
non-magnetised objects are able to be attracted
to magnets.
Magnetism
28
Unit 12.2
Magnetic Induction
Induced Magnetism Here is another example
of induced magnetism.


Magnetism
29
Unit 12.2
Magnetic Induction
Induced Magnetism

Using the theory of induced magnetism, explain
how it is possible to get several iron nails to
stick together (as shown in the diagram below).
Magnetism
30
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism 12.4 Methods of Magnetisation 12.5 Metho
ds of Demagnetisation 12.6 Magnetic
Fields 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
31
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism
If a piece of magnet is dropped broken into 2
or more pieces, each piece is noticed to behave
just like the original magnet. It is able to
exhibit all the properties of a magnet.
Magnetism
32
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism
If each piece of magnet is again dropped broken
into more smaller pieces, each smaller piece is
still noticed to behave just like the original
magnet. They are all able to exhibit all the
properties of a magnet.
Magnetism
33
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism

It follows that if this breaking process is
continued, each ever smaller piece is still a
magnet. Thus, it is only reasonable to assume
that an original magnet is made up of many tiny
magnets, all lined up with the same magnetic
orientation (i.e. all of the tiny magnets have
their N-pole facing the same direction).
Magnetism
34
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism
A few adjacent tiny magnets are usually aligned
in the same magnetic orientation. This group of
tiny magnets form a magnetic domain.
Magnetism
35
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism
A few adjacent tiny magnets are usually aligned
in the same magnetic orientation. This group of
tiny magnets form a magnetic domain. In an
unmagnetised object made of magnetic
material, magnetic domains do not have the same
magnetic orientation.
Magnetism
36
Unit 12.3
Magnetic Domain Theory
A Theory of Magnetism
In an unmagnetised object made of magnetic
material, magnetic domains do not have the same
magnetic orientation. It thus explains why
unmagnetised objects of magnetic material do not
exhibit properties of a magnet.
Magnetism
37
Unit 12.3
Magnetic Domain Theory
Storage of Magnets using Keepers
Using the theory of magnetism, we are now able to
explain why magnets which are not used are
usually stored using keepers.
Magnetism
38
Unit 12.3
Magnetic Domain Theory
Storage of Magnets using Keepers
Using the theory of magnetism, we are now able to
explain why magnets which are not used are
usually stored using keepers. The free poles
near the end of magnets repel each other. As time
passes, the magnet becomes weaker.
Magnetism
39
Unit 12.3
Magnetic Domain Theory
Storage of Magnets using Keepers
Using the theory of magnetism, we are now able to
explain why magnets which are not used are
usually stored using keepers. The free poles
near the end of magnets repel each other. As time
passes, the magnet becomes weaker. To prevent
this weakening, bar magnets are stored in pairs
by using keepers (2 pieces of soft iron) across
the ends of the bar magnets.
keepers(which are induced magnets in this case)
Magnetism
40
Unit 12.3
Magnetic Domain Theory
Storage of Magnets using Keepers
Ever wonder why the 2 permanent magnets are
always placed with unlike poles facing each
other? (Hint)
N
S
N
S
N
S
N
S
Magnetism
41
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Have you ever wonder if a magnet can be made
stronger stronger with no possibility of
reaching a point of maximum strength?
Magnetism
42
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Have you ever wonder if a magnet can be made
stronger stronger with no possibility of
reaching a point of maximum strength? Scientifica
lly, this is impossible to achieve.
Magnetism
43
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Imagine yourself holding a piece of unmagnetised
magnetic material now.
Magnetism
44
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Start magnetising it now (by stroking it with a
simple bar magnet).
Magnetism
45
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
After some time, some magnetic domains begin to
have the same magnetic orientation. Continue
magnetising it.
Magnetism
46
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Very soon, most magnetic domains will have the
same magnetic orientation. Continue magnetising
it.
Magnetism
47
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
Finally, all the magnetic domains are aligned in
the same magnetic orientation. Continue
magnetising it.
Magnetism
48
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
No matter how long you continue to magnetise
it, the magnet can no longer become stronger as
all initial magnetic domains are already aligned
in the same orientation.
Magnetism
49
Unit 12.3
Magnetic Domain Theory
Magnetic Saturation
At this moment, the magnet is said to have
reached Magnetic Saturation.
Magnetism
50
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation 12.5 Methods of Demagnetisation 12.6
Magnetic Fields 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
51
Unit 12.4
Methods of Magnetisation
Magnetisation
Making a material permanently magnetic is called
magnetisation. There are several ways to
magnetise materials.
Magnetism
52
Unit 12.4
Methods of Magnetisation
Magnetisation by Stroking (Single-Touch)
This method is derived from applying the lessons
learnt on magnetic induction. Note the
polarities of both the permanent magnet steel
bar that is to be magnetised. This form of
magnetism gained is weak but permanent.
Magnetism
53
Unit 12.4
Methods of Magnetisation
Magnetisation by Stroking (Double-Touch)
This method is also derived from applying the
lessons learnt on magnetic induction. 2
permanent magnets are used in this method, as
compared to one being used in the single-touch
stroking method. Note the polarities of both
permanent magnets. Once again, do take note of
the polarities of the permanent magnets their
induced ends of the steel bar. This form of
magnetism gained is also weak but permanent.
Magnetism
54
Unit 12.4
Methods of Magnetisation
Magnetisation by Heating Hammering
A magnet can be made by first placing a steel bar
in a magnetic field, then heating it to a high
temperature and then finally hammering it as it
cools. This can be done by laying the magnet in
a North-South direction in the Earths magnetic
field. However, the magnet produced is not very
strong but permanent.
Magnetism
55
Unit 12.4
Methods of Magnetisation
Magnetisation by the use of an Electrically-gener
ated magnetic field of a Solenoid
Place the steel object inside a coil of wire (a
solenoid). Pass a direct current (d.c.) through
the solenoid for a few seconds. A magnetic field
is produced on the solenoid. As such, the steel
rod is now placed inside a magnetic field. When
the current is turned off the steel rod is found
to be magnetised. Note the d.c. flows through
the solenoid. It does not flow through the steel
rod.
steel rod
Magnetism
direct current
56
Unit 12.4
Methods of Magnetisation
Magnetisation by the use of an Electrically-gener
ated magnetic field of a Solenoid
The polarity of the newly-formed magnet can be
determined using the Right-hand Grip
Rule. (Fingers coiled round following the
direction of the flow of d.c. in the solenoid
the thumb will point in a direction indicating
the end which becomes the N-pole).
Magnetism
57
Unit 12.4
Methods of Magnetisation
Magnetisation by the use of an Electrically-gener
ated magnetic field of a Solenoid
The polarity of the newly-formed magnet can also
be determined using the method Take a look at
which way the d.c. is flowing at each end. If the
direction of flow is anticlockwise, the end is a
N-pole. If the direction of flow is clockwise,
the end is a S-pole.
Magnetism
58
Unit 12.4
Methods of Magnetisation
Magnetisation by the use of an Electrically-gener
ated magnetic field of a Solenoid
The magnetism produced using this method is
strong permanent.
Magnetism
59
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation 12.6 Magnetic Fields 12.7 Magnetic
Properties of Iron Steel 12.8 Uses of
Permanent Magnets Electromagnets
60
Unit 12.3
Magnetic Domain Theory
Demagnetisation
The process of weakening a magnets strength
(removing magnetism) is known as
demagnetisation. When some magnetic domains are
no longer in the same magnetic orientation as the
rest of the domains, the magnets strength
weakens. When all the magnetic domains are no
longer in the same magnetic orinetation, the
magnet is completely demagnetised. It is now a
piece of magnetic material with no magnetism in
it.
Magnetism
61
Unit 12.5
Methods of Demagnetisation
Demagnetisation by Heating Hammering
Heat a magnet. Then hammer it as it is allowed
to cool in the absence of a magnetic field i.e.
facing East-West .
Magnetism
62
Unit 12.5
Methods of Demagnetisation
Demagnetisation by the use of an
Electrically-generated magnetic field of a
Solenoid
(700 turns)
magnet withdrawn to a few metres
Magnetism
63
Unit 12.5
Methods of Demagnetisation
Demagnetisation by the use of an
Electrically-generated magnetic field of a
Solenoid
(700 turns)
magnet withdrawn to a few metres
Place magnet in a solenoid. Pass an alternating
current (a.c.) through the solenoid (not through
the magnet). Slowly remove the magnet from the
solenoid with the a.c. supply still on. Remove to
a great distance. Repeat the procedure for as
many times as it is necessary. Each time it is
done, the magnets strength weakens. Finally, it
is completely demagnetised.
Magnetism
64
Unit 12.5
Methods of Demagnetisation
Demagnetisation by the use of an
Electrically-generated magnetic field of a
Solenoid
(700 turns)
magnet withdrawn to a few metres
Place magnet in a solenoid. Pass an alternating
current (a.c.) through the solenoid (not through
the magnet). Slowly remove the magnet from the
solenoid with the a.c. supply still on. Remove to
a great distance. Repeat the procedure for as
many times as it is necessary. Each time it is
done, the magnets strength weakens. Finally, it
is completely demagnetised.
Magnetism
65
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation (Completed) 12.6 Magnetic
Fields 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
66
Unit 12.6
Magnetic Fields
Magnetic Field
A magnetic field is the region where a magnetic
force is exerted on any magnetic objects placed
within the influence of the field.
Showing the Magnetic Field Using Iron a
Filings One method to observe the shape of the
magnetic field is by sprinkling iron filings onto
a piece of paper placed on top of the magnet.  
Magnetism
67
Unit 12.6
Magnetic Fields
Plotting Compass A compass is a freely suspended.
A compass is normally drawn with the N-pole shown
as an arrowhead. It can be used to find the
direction of a magnetic field.   Remember the
N-pole of the compass points to the Earths
N-pole.   The Earths magnetic field is produced
by electric currents at its core. It is similar
to the field that would be due to an imaginary
large bar magnet in the Earths centre.

Magnetism
68
Unit 12.6
Magnetic Fields

N
S
What do you think are the directions that the
compass would point in if placed in the ten
different points around a strong permanent magnet?
Magnetism
69
(No Transcript)
70
Unit 12.6
Magnetic Fields
Magnetic Field Lines
Magnetic field lines are imaginary represent
the direction of the magnetic field. Magnetic
field lines are also known as lines of
force because if magnetic objects are placed in
the region of the field lines, the magnetic
objects will experience a magnetic force directed
along the same lines. By convention, the
magnetic field line is the path along which an
imaginary free N-pole will move if placed along
this line.

Magnetism
71
Unit 12.6
Magnetic Fields
Neutral Point
Whenever a point in space has no magnetic
field the magnetic field due to one magnet
cancels out that due to another magnet, this
point is known as a Neutral Point.

neutral point
Magnetism
72
Unit 12.6
Magnetic Fields
Plotting Magnetic Field Lines With A Plotting
Compass The lines can be investigated to find
their path and direction using a plotting
compass. Place a plotting compass at point
A. Note the direction it points at. Mark a 2nd
point next to the N-pole of the plotting compass.

2
Magnetism
73
Unit 12.6
Magnetic Fields
Plotting Magnetic Field Lines With A Plotting
Compass The lines can be investigated to find
their path and direction using a plotting
compass. Place a plotting compass at point
A. Note the direction it points at. Mark a 2nd
point next to the N-pole of the plotting
compass. These steps are repeated as shown. The
points are all joined using a pencil. All these
steps are repeated for other points next to the
N-pole of the magnet.

Magnetism
74
Unit 12.6
Magnetic Fields
Examples of Magnetic Fields
(i) A permanent bar magnet.

Magnetism
75
Unit 12.6
Magnetic Fields
Examples of Magnetic Fields
(ii) 2 opposite poles facing each other

Magnetism
76
Unit 12.6
Magnetic Fields
Examples of Magnetic Fields
(iii) 2 like poles facing each other (e.g. 2
N-poles)

Magnetism
77
Unit 12.6
Magnetic Fields
Neutral Point
If a plotting compass is placed at the neutral
point (i.e. X), how will it point?

Magnetism
78
Unit 12.6
Magnetic Fields
Magnetism
79
Unit 12.6
Magnetic Fields
Properties of Field Lines         Lines always
start and end on the magnet.         The lines
travel from the N-pole to the S-pole.        
The lines never cross or touch each
other.         The closer the lines the stronger
the field. (More magnetic field lines do not
necessarily mean stronger magnetic field)
Magnetism
80
Unit 12.6
Magnetic Fields
Try labelling the poles of the following magnets.
Magnetism
81
Unit 12.6
Magnetic Fields
These are possible answers.
N
S
N
N
S
N
N
S
S
N
N
N
S
N
S
S
Magnetism
82
Unit 12.6
Magnetic Fields
These are also possible answers.
S
N
S
S
N
S
S
N
N
S
S
S
N
S
N
N
Magnetism
83
Unit 12.6
Magnetic Fields
Magnetic Shielding Magnetic fields are sometimes
not wanted and can damage delicate equipment such
as watches, televisions, computer disks,
etc..   Shielding is achieved by surrounding the
object with soft iron. The lines of magnetic
force concentrate in the soft iron.
Magnetism
closed soft iron sphere
84
Unit 12.6
Magnetic Fields
Magnetic Shielding
Magnetism
85
Unit 12.6
Magnetic Fields
Magnetic Shielding
A powerful source of magnetism is a loudspeaker
as it contains a very powerful magnet. How is
it that some speakers are now designed to sit on
top of a television screen (a device easily
damaged by a magnetic field) without damaging
them?
Magnetism
86
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation (Completed) 12.6 Magnetic Fields
(Completed) 12.7 Magnetic Properties of Iron
Steel 12.8 Uses of Permanent Magnets
Electromagnets
87
Unit 12.7
Magnetic Properties of Iron Steel
Although iron and steel are both magnetic
materials, their properties are different.

• Two unmagnetised rods have a magnet placed on top
  of them.
• Iron filings are supported from the induced
  magnets

Magnetism
88
Unit 12.7
Magnetic Properties of Iron Steel

• Note that the induced magnet made of iron
  attracts more iron filings than the induced
  magnet made of steel

Magnetism
89
Unit 12.7
Magnetic Properties of Iron Steel

• The permanent bar magnet is then removed.

Magnetism
90
Unit 12.7
Magnetic Properties of Iron Steel

• Note that the iron bar no longer has any iron
  filings attracted to it.
• The steel bar, however, still has some iron
  filings attracted to it.

Magnetism
91
Unit 12.7
Magnetic Properties of Iron Steel

• Magnetic properties of Iron Steel
• Iron is easily magnetised, whereas Steel is not
  easily magnetised.

Magnetism
92
Unit 12.7
Magnetic Properties of Iron Steel

• Magnetic properties of Iron Steel
• Iron is easily demagnetised, whereas Steel is
  not easily demagnetised.

Magnetism
93
Unit 12.7
Magnetic Properties of Iron Steel
Magnetic properties of Iron Steel Iron is
thus known as a soft magnetic material (easily
magnetised easily demagnetised).
Magnetism
94
Unit 12.7
Magnetic Properties of Iron Steel
Magnetic properties of Iron Steel Steel is
however known as a hard magnetic
material (difficult to magnetise difficult to
demagnetise). Iron is thus used in making
electromagnets steel is thus used in making
permanent magnets.
Magnetism
95
Unit 12.7
Magnetic Properties of Iron Steel
Magnetic properties of Iron Steel Iron is
thus used in making electromagnets steel is
thus used in making permanent magnets.
Magnetism
96
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation (Completed) 12.6 Magnetic Fields
(Completed) 12.7 Magnetic Properties of Iron
Steel (Completed) 12.8 Uses of Permanent Magnets
Electromagnets
97
Unit 12.8
Uses of Permanent Magnets
Permanent magnets have many uses. Permanent
Magnets
Magnetism
98
Unit 12.8
Uses of Permanent Magnets
Permanent magnets have many uses. Permanent
Magnets
Magnetism
99
Unit 12.8
Uses of Permanent Magnets
Permanent magnets have many uses. Permanent
Magnets
Magnetism
100
Unit 12.8
Uses of Permanent Magnets
Permanent magnets have many uses. Permanent
Magnets
Speaker
Magnetism
101
Unit 12.8
Uses of Electromagnets
Electromagnets have many uses too. Electromagnets
The electric-bell
Magnetism
102
Unit 12.8
Uses of Electromagnets
Electromagnets have many uses too. Electromagnets
A simple magnetic-relay
Magnetism
103
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation (Completed) 12.6 Magnetic Fields
(Completed) 12.7 Magnetic Properties of Iron
Steel (Completed) 12.8 Uses of Permanent Magnets
Electromagnets (Completed)
Magnetism
104
Chapter 12
Magnetism
Contents 12.1 Materials Magnets
(Completed) 12.2 Magnetic Induction
(Completed) 12.3 Magnetic Domain Theory of
Magnetism (Completed) 12.4 Methods of
Magnetisation (Completed) 12.5 Methods of
Demagnetisation (Completed) 12.6 Magnetic Fields
(Completed) 12.7 Magnetic Properties of Iron
Steel (Completed) 12.8 Uses of Permanent Magnets
Electromagnets (Completed)
Magnetism