# TOPIC 4. MAGNET AND MAGNETISM

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MAGNETISM
HISTORY OF MAGNETISM
The ancient Greeks were the first
known to have used this mineral,
which they called a magnet because of
its ability to attract other pieces of the
same material and iron.
• William Gilbert (1540-1603)
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He was the first to investigate the phenomenon of magnetism.
MAGNET
It is an object that has a strength
to attract magnetic materials. This
means that a magnet does not
attract all materials, it only
attracts materials which have a
property to get attracted to or
interact with a magnet.
What are the types of magnet?
Natural magnet
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Have no regular shape and size.
Weak magnets
Artificial magnets
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They are made of materials like iron,
cobalt, and nickel.
Strong magnets
They can be made in different shapes
and sizes.
Properties of Magnets
It can attract materials that are
magnetic in nature.
The forces of attraction are produced
by the ends of the magnet.
Magnetic Poles
Magnetic axis – a
straight line that acts
as a junction between
the north and south
poles.
All strongly magnetic materials
contain Iron, Nickel and Cobalt. They
are called ferromagnet.
Opposite poles are attracted to each
other, while the same poles repel each
other.
What is the difference between permanent
and induced magnets?
• Permanent magnets never lose their
magnetism.
• Induced magnets have a temporary
magnetic force.
WHAT IF WE BREAK A MAGNET IN
HALF?
Magnetism
Is a force, like gravity and the strong
and weak forces inside the nucleus of
an atom. Magnetic forces pull and
push objects by generating the socalled magnetic field.
MAGNETIC FIELD
A magnetic field is the area around a
magnet where it exerts its force.
The lines are called magnetic field lines.
Magnetic flux is the number of filled lines per area.
International System of Units
The SI unit of the magnetic field strength (B) is the
tesla (T)
In honor of the Serbian-American physicist
NIKOLA TESLA (1857-1943)
One (1) tesla = One (1) newton per ampere-meter
International System of Units
The SI unit of the magnetic flux (B) is the weber (Wb)
In honor of the German physicist WILHELM
WEBER (1804-1891).
One (1) weber = One (1) tesla square meter
QUIZ #1
1. Daniel hangs steel paper clips at different
places on a bar magnet.
Complete the following sentence: The
magnetic force is ______________.
A. weakest in the middle
B. strongest in the middle
C. weakest at the poles
2. Magnets create magnetic fields. We can use
iron filings to show the magnetic field around a bar
magnet.
What does this image show us about the magnetic
field?
A. It is strongest at the poles.
B. It is the same in all areas on the magnet.
C. It is weakest at the poles.
3. A simple compass is a magnetic needle
mounted on a pivot or a short pin. The needle
can spin freely.
Which direction does the needle on a
compass always point to?
A. South
B. North
C. West
D. East
4. It is the straight line that acts as a junction
between the north and south poles.
A. South poles
B. North poles
C. Magnetic axis
D. Magnetic flux
5. What happens when the south poles of two
magnets are brought together?
A. Nothing happens.
B. They attract each other.
C. They repel each other.
6. Isabella is drawing 2 magnets that attract each
other.
She forgets to color in or label the poles on the
2nd magnet. Which image correctly shows the
second magnet?
A.
B.
7. What is the name of the region around a
magnet where the magnetic force acts?
A. The compass
B. The poles
C. The magnetic needle
D. The magnetic field
8. A bar magnet has two poles. What do we
call them?
A. North and west
B. East and west
C. North and south
D. South and east
9. It is a force, like gravity and the strong and
weak forces inside the nucleus of an atom.
A. Ferromagnet
B. Poles
C. Magnet
D. Magnetism
10. Who was the first to investigate the
phenomenon of magnetism.
A. Albert Einstein
B. Nikola Tesla
C. William Gilbert
D. Wilhelm Weber
“That’s in all things, God may be glorified.”
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