Download Magnetism

Electromagnetism
Magnetism
• Magnetism is defined as the properties and
interaction of magnets.
• Magnets will attract or repel each other,
depending on the location of the magnetic
poles.
• Like poles repel, and opposite poles attract.
Magnetic fields flow from the north
pole to the south pole of a magnet.
http://en.wikipedia.org/wiki/Compass
http://en.wikipedia.org/wiki/File:Magnetic_field.svg
Earth’s Magnetic Field
• A compass lines up with
Earth’s magnetic field.
• The north end of a compass
points towards geographic
North, but points towards
the south magnetic pole.
• The south end of a compass
points towards geographic
South but points towards
the north magnetic pole.
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Electricity and Magnetism
• Electric charges (negative charges) at rest have an
electric field around them. The field draws
positive charges toward them, and negative
charges are repelled.
• Moving charges, or current, create a magnetic
field around a wire. The direction of the field is
determined by the direction of the current flow.
• Moving charges have both an electric field and
a magnetic field around them.
Electromagnets
• An electromagnet is a temporary magnet
made by wrapping a wire coil carrying a
current around an iron core.
• It is a temporary magnet that behaves like a
magnet as long as there is current flowing
through the solenoid coils.
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Generators
• Change movement into electricity
• Have an electromagnetic coil that rotates
because of an outside source of mechanical
energy (wind, water, etc.)
• The current is created from the moving of the
coil through the field of a permanent magnet.
Electric Motor
• Change electricity into movement
• The electromagnetic coil rotates due to
attractive and repulsive forces between the
coil and the permanent magnet.
• The current in the wire comes from an outside
source (gasoline, coal, natural gas).
Transformers
• Devices that increase or decrease the voltage of
an alternating current. This is done by wrapping
input and output coils around an iron core.
• Step-Up Transformer: Increases the voltage so
that the output voltage is greater than the input
voltage (more coils for output)
• Step-Down Transformer: Decreases the voltage
so that the output voltage is less than the input
voltage (less coils for output)
Transformers (continued)
Image: http://en.wikipedia.org/wiki/Transformer