Transcript Magnetism Notes

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Investigate applications of magnetism and its
relationship to the movement of electrical
charge as it relates to
• electromagnets
• simple motors
• permanent magnets
• electromagnetic induction
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Magnetism is the
force of attraction or
repulsion due to electron
motion.
4 Magnets have two poles, a north
pole and a south pole.
Unlike magnetic poles attract each other, while like magnetic
poles
repel each other.
5Groups of atoms with magnetic poles
aligned are called magnetic domains.
Materials
with most of
the domains
lined up are
considered
magnetized.
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The more domains that
are aligned, the stronger
the magnetic field in the
material.
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Magnetic Field lines were introduced by Michael
faraday , who named them ‘’lines of force.’’
Sketch
this one
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Permanent Magnets
• A magnet made
from materials that
keeps its
magnetism for a
long time is a
Permanent
Magnets.
• Examples are
refrigerator magnets
and neodymium
magnets
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Temporary Magnets
• Materials that become
magnetized for a
short time.
• Temporary Magnets
can be magnetized by
rubbing the material
in one direction.
• Paper Clips are
examples of
temporary Magnets
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Magnetic Materials
• Ferromagnetic Materials
have strong magnetic
properties. Examples are
iron, nickel, and cobalt
• Ferrous Metals are alloys,
a mix of different metals.
Iron is a part of this mix.
• Both Ferromagnetic
Materials and Ferrous
Metals are attracted
to magnets.
Magnetism From Electricity
A connection between electricity and magnetism was
discovered (accidentally) over 100 years ago, it was
noticed that a compass needle is deflected when
brought into the vicinity of a current carrying wire. Thus,
currents can induce a magnetic field.
An electromagnet is simply a coil of wires which, when
a current is passed through, generate a magnetic field,
as below.
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Current gives rise
to magnetic fields,
just as electric
charge gave rise to
electric fields
Electromagnet
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The basic idea behind an
electromagnet is extremely
simple: By running electric
current through a wire, you can
create a magnetic field.
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Electricity through the coiled wire
creates a magnetic field which induces
magnetism in the iron core. The domains
in the core become aligned with the
magnetic field of the coil. The more
coils, the stronger the magnet.
Electromagnets
15 A rotating electromagnet is used in
an electric motor to convert electrical
energy to mechanical energy.
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When a magnet is moved near
a wire, an electric current can
be created. This process is
called electromagnetic
induction. Electromagnetic
induction is used in the
operation of a generator, a
device that converts
mechanical energy to
electrical energy. In a
generator, an electric current
is produced when a coil of
wire is rotated in a magnetic
field.
Generating
electricity:
•coil of wire
rotated in a
magnetic field
•magnet is
moved near a
wire
The use of magnetic waves to make pictures of the inside of the
body. Using a large magnet, radio waves, and a computer, an MRI
produces two-dimensional and three-dimensional pictures.
July 3, 1977
Which of these
correctly identifies
both devices
illustrated?
A Picture A: electric generator;
Picture B:electromagnet
B Picture A: electromagnet;
Picture B: electric motor
C Picture A: electric motor;
Picture B: electromagnet
D Picture A: electric generator;
Picture B: electric motor
A magnetic field can be found in which
of the following?
A electric motor
B sound wave
C plastic cord
D glass rod
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Properties of Magnets
• If a magnet is cut in half, you will have two
magnets, each with a north and south
pole.
 Forcefully hitting or dropping a permeant
magnet can cause the domain to
unaligned. This causes the magnet will
lose its magnetism, become unmagnified.
• Similarly, heating a magnet will also
destroy its magnetism.
TOTD
1. What is magnetism?
2. Draw the domains of an un-magnetized
material.
3. Draw the domains of a magnetized
material.
4. What’s the difference between a
permanent magnet and a temporary
magnet?
5. What will happen if a magnet is cut in half
6. List 2 ways to destroy a magnet.