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## Electromagnetism (S8P5 b, c)

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### Electromagnetism (S8P5 b, c) Physical Science Candace Black Spring, 2010 Electric Current and Magnetism Electric current produces a magnetic field. – PowerPoint PPT presentation

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Title: Electromagnetism (S8P5 b, c)

1
Electromagnetism(S8P5 b, c)
• Physical Science
• Candace Black
• Spring, 2010

2
Electric Current and Magnetism
Can you identify the 3 necessary parts of a
circuit?
• Electric current produces a magnetic field.
• The relationship between electricity and
magnetism is called electromagnetism

3
Solenoids
• 3 characteristics of magnetic field
• produced by current
• 1. Can be turned on or off.
• 2. Direction can be reversed.
• 3. Strength can be changed.
• A coil of wire with a current is called a
solenoid.

4
Electromagnets
• A solenoid with a ferromagnetic core is called
and electromagnet.
• Magnetic field is produced by both the current in
the wire and the magnetized core.
• A strong magnet that can be turned on and off.
• Increase strength by
• 1. Increasing current
• 3. Place coils closer together
• 4. Use stronger ferromagnetic material
as core.

5
Uses of Electromagnets
• Audiotapes, videotapes, computer hard drives,
credit cards
• Doorbell
• Fire doors(be able to explain how these work in
our school)
• To lift heavy objects such as junk cars, metal
containers such as are used in shipping, etc.

6
Electric Motors
• A device that uses an electric current to turn an
axle.
• Transforms electrical energy into mechanical
energy.

7
In your notes, write at least 3 things that you
can think of that use motors.
8
Induction of Current
• Electric current is induced in a conductor when
the conductor moves through a magnetic field.
• Generating an electric current from the motion of
a conductor through a magnetic field is called
electromagnetic induction.
• Current that is generated in this way is called
induced current.

9
Induced Currents
• A current consisting of charges that flow in one
direction only is called a direct current or DC.
• Example battery operated items charges flow
from positive end through circuit back to
negative end.
• A current that flows back and forth in a circuit
is called an alternating current or AC.
• Example homes, buildings, schools,
• Advantage voltage can be raised or lowered
higher voltages can travel over longer distances
(from power plant) then can be lowered for
everyday use (in our homes).

10
Generators
• An electric generator is a device that transforms
mechanical energy into electrical energy.
• A generator uses motion in a magnetic field to
produce an electric current.
• Electric motors use and electric current in a
magnetic field to produce motion.
• Generators are used in power plants with turbines
acting as the crank.

Be able to compare/contrast generators and motors.
11
Transformers
• A transformer is a device that increases or
decreases voltage. (voltage is?)
• Consists of 2 separate coils of insulated wire
wrapped around an iron core.
• Two types of transformers are
• 1. step-up transformer increases
• voltage.
• 2. step-down transformer decreases
• voltage.

12
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