What is a magnet Magnet Permanent Magnets By shape Material Temporary magnets Electromagnets 1 ALL magnets have NORTH and south poles 2 When freely suspended all magnets point to the north Directional property ID: 617061
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Slide1
TP
Students to understand the properties of magnets.Slide2
What is a magnet?
Magnet
Permanent Magnets
By shape
Material
Temporary magnets?
ElectromagnetsSlide3
1. ALL magnets have NORTH and south poles.
2. When freely suspended, all magnets point to the north- Directional property.
NORTH
seeking
pole
SOUTH
seeking
pole
PROPERTIES OF MAGNETSSlide4
Classwork(Page 224-230)
What are magnetic materials. State example of magnetic materials.
What are non-magnetic materials. State examples of non-magnetic magnetic materials.
Explain what is meant by:
ferrous and non-ferrous materials. Give examples of each.
Hard and soft magnetic materials. Give examples of each. Slide5
What is a Magnetic field
Magnetic field patterns for:Slide6
Magnetic materials.
Materials that can be attracted by a magnet
.
These include:
Iron(steel), Nickel, Cobalt or their alloys
ONLY.
Non-magnetic materials
.
Materials that do not feel a magnetic force.Example: wood, copper, aluminium, rubber, water, wool, paper,Slide7
FERROUS MATERIALS
These are materials that contain
iron
in them.
Example
: Steel, stainless steel, invar.
Most ferrous materials are magnetic.
NON-FERROUS MATERIALS
These are materials
that do not
contain
iron in them.
Example:
Nickel and cobalt which are magnetic.Most non-ferrous materials are non-magnetic.Slide8
THE LAW OF MAGNETISM
Like poles repel, unlike poles attract.Slide9
Breaking a magnet produces two magnets.
N
S
N
S
N
N
S
S
Repeated breaking will create a smallest magnet
atomic magnet(dipole)Slide10
Un-magnetized material
Domains are not arranged in any order.
Magnetized material
Domain aligned in one direction.Slide11
MAGNETIZATION
A process of making of magnets.
There are 3 methods of magnetising;
1. Stroking or touching.
2. Electrical method.
3. Magnetic induction.
A process of making of magnets by creating N-S poles on each end a magnetic bar.Slide12
Methods of magnetizationSlide13
Magnetic induction
When a magnetic material is close to a magnet, it becomes a magnet itself
We say it has
induced magnetism
N
S
N
S
magnetSlide14
Soft Magnetism
Pure iron
is a
soft
magnetic material
It is easy to magnetise iron but loses its magnetism easily.
It is used to make (temporal) electromagnets
N
S
before
after
Iron nail
S
N
N
S
Not
a magnet
NSlide15
Hard Magnetism
Steel
is a
hard
magnetic material
It is harder to magnetise, but keeps its magnetism (it is used to make permanent magnets!)
N
S
before
after
Steel paper clip
N
N
S
It’s a magnet!
N
S
S
NSlide16
Magnetic fields
The space around a magnet where it’s magnetic force is felt.
The magnetic field is shown by
field lines
running from North pole to south pole
Slide17
Magnetic field Patterns
Slide18
A magnet has strong field at the poles.Slide19
ELECTROMAGNETS
An
ELECTROMAGNET
is a magnet that can be switched on and off by an electric current.
Switch On
: Current flows and the nails becomes a magnet.
Switch Off:
No current and the nail looses its magnetism.Slide20
Increasing the strength of electromagnets
1.
Increase amount of current.
More current produces stronger electromagnet
2.
Increase number turns of the coil.
3.
Using soft Iron core.