Transcript electric motor - Madison County Schools

Electricity,
Magnetism, and
Motion
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Notes
Electric Current and
Magnetism
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Wherever there is electricity, there is
magnetism.
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An electric current produces a magnetic field.
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This relationship between electricity and
magnetism is known as electromagnetism.
Solenoids
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The magnetic field produced by a current can
change in 3 ways:
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On/Off
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Direction
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Strength (add loops to the coil)
Solenoids
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A coil of wire with a current is called a
solenoid.
Electromagnets
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A solenoid with a ferromagnetic core
(Iron-magnet) is called an electromagnet.
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The overall magnetic field of an
electromagnet can be hundreds or
thousands of times stronger than the
magnetic field produced by the current
alone.
•
An electromagnet is a strong magnet that
can be turned on or off.
Electrical Energy and
Motion
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A magnet can move a wire with a current. The
magnetic field of the magnet interacts with the
magnetic field of the wire with a current. The
result is that the wire moves.
Electrical Energy and
Motion
•
A magnet can move a wire with a current. The
magnetic field of the magnet interacts with the
magnetic field of the wire with a current. The
result is that the wire moves.
Electrical Energy and
Motion
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The ability to move an object is called energy.
The energy of electric currents is called
electrical energy.
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The energy of motion is called mechanical
energy.
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Electrical energy changes into mechanical
energy when a wire with a current is placed in a
magnetic field. The electrical energy produces
the magnetic field in the wire with a current. The
movement that results is mechanical energy.
Galvanometers
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A galvanometer is a device that measures
small currents.
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A galvanometer contains an electromagnet.
The electromagnet is between the opposite
poles of two permanent magnets.
Galvanometers
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A current in the EM produces a magnetic
field. The EM’s magnetic field interacts
with the magnetic fields of the permanent
magnets. This interaction causes the EM
to move.
•
A pointer is attached to the EM in a
galvanometer. When the EM moves, the
pointer moves. A scale shows how much
the pointer moves. The current through the
EM is measured on the scale.
Electric Motors
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An electric motor uses an electric current
to turn an axle. The axle is a rod. For
example, an electric motor turns the axle
of a fan. The fan blades are connected to
the turning axle.
Electric Motors
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The name for the wire (or wire loops) that
contains the current and rotates is known as
the armature.
Electric Motors
Electric Motors
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An electric motor works by changing electrical
energy into mechanical energy.
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In an electric motor, a loop of wire spins
continuously. It spins continuously by changing the
direction for the current at each half turn of the
loop. Every half turn of the axle, the current
reverses. First it goes one way, and then it goes
the opposite way.
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The part of an electric motor that reverses the
current is called a commutator. A commutator is a
ring split in half.
Electric Motors
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As the commutator rotates with the armature, it
slides past two contact points called brushes.
Each half of the commutator is connected to the
current source by one of the brushes.
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As the armature rotates, each part of the
commutator contacts one brush, then the other.
Because the brushes conduct the current,
changing brushes reverses the direction of the
current in the armature.
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The reversing of the direction of the current causes
the armature to spin continuously.