Transcript Magnetism ppt

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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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Field lines were introduced by michael faraday ,
who named them ‘’lines of force.’’
Sketch
this one
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9 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.
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.
Electromagnets
12 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.
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Generating
electricity:
•coil of wire
rotated in a
magnetic field
•magnet is
moved near a
wire
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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
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Which of these
correctly identifies
both devices
illustrated?
A Picture A: electric generator;
Picture B:electromagnet
B Picture A: electromagnet;
Picture B: electric generator
C Picture A: electric motor;
Picture B: electromagnet
D Picture A: electric generator;
Picture B: electric motor
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A magnetic field can be found in which
of the following?
A electric motor
B sound wave
C plastic cord
D glass rod