# Electromagnetism - PowerPoint PPT Presentation

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## Electromagnetism

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### Electromagnetism Electromagnetism The branch of physics that deals with the relationship between magnetism and electricity. A charge at rest produces no magnetic field. – PowerPoint PPT presentation

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Title: Electromagnetism

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Electromagnetism
2
Electromagnetism
• The branch of physics that deals with the
relationship between magnetism and electricity.

3
A charge at rest produces no magnetic field.
Electrons that flow through a wire produce a
magnetic field about that wire. The magnetic
field is represented by imaginary lines that form
concentric circles centered on the wire
4
These same rules apply if the current is in a
loop. Magnetic field lines form concentric
circles around each tiny section of the wire.
Because the wire is curved, however, these
magnetic field lines overlap inside the loop. In
particular, at the very center of the loop, all
the field lines come together, making the
magnetic field strong
Stacking more loops on top of each other
increases the intensity of the magnetic field
running through the center or axis of the stack
of loops. The magnetic field of a solenoid is
concentrated through the center of the coil. A
coil of wire is called a solenoid.
5
The magnetic field can be intensified further by
wrapping the coil of wire around ferromagnetic
material, such as iron. The iron core intensifies
the magnetic field. In this case, almost all of
the magnetic field lines are concentrated inside
the iron core, escaping only near the ends of the
coil. This type of device is called an
electromagnet.
An electromagnet is a current-carrying coil of
wire wrapped around an iron core, which
intensifies the induced magnetic field.
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The magnetic field produced by an electromagnet
is the same as that produced by a bar magnet.
That is, if both were hidden from view behind a
piece of paper, the pattern of magnetic field
lines revealed by iron filings sprinkled on the
paper surface would be the same. Of course, the
advantage of the electromagnet is that its
magnetic field can be adjusted or turned on and
off simply by varying the current through its
coil of wire.
Can magnetic fields somehow be used to generate
British experimenter, found the answer to that
question.
8
Electromagnetic induction An electric current is
induced in a circuit if some part of that circuit
is in a changing magnetic field.
FARADAY'S LAW The magnitude of the induced
current depends on four factors 1.The strength
of the magnetic field 2.The velocity of the
magnetic field as it moves past the
conductor 3.The angle of the conductor to the
magnetic field 4.The number of turns in the
conductor
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Actually, no physical motion is needed. An
electromagnet can be fixed near a coil of wire.
If the current in the electromagnet is then
increased or decreased, its magnetic field will
likewise change and induce a current in the coil.
11
ELECTRIC GENERATOR ( Dynamo)A device that
converts mechanical energy to electrical energy
by electromagnetic induction.
Generator components1. Powerful magnet 2.
Armature (wire loop)
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A/C generator
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D/C generator
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ELECTRIC MOTOR-A device that converts electrical
energy to mechanical energy by electromagnetic
induction.
Generator components1. Powerful magnet 2.
Armature (wire loop) 3. Source of electrical
energy
15
D/C motor
16
Induction motor A/C
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