transformer - Madison County Schools

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Transcript transformer - Madison County Schools

Electricity from
Magnetism
•
Notes
Induction of Electric Current
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Motion can produce electrical energy. Suppose you
move a conductor, such as a wire, through a
magnetic field. By doing this, you will create an
electrical current in the conductor.
•
Electromagnetic induction is when an electric
current is created in a conductor by moving the
conductor through a magnetic field. This is called
“inducing a current.” Current that is made by moving
a conductor through a magnetic field is called
induced current.
Induction of Electric
Current
•
You can induce a current in two ways:
-You can move the conductor through the
magnetic field.
-You can move a magnet through a coil of wire.
Induction of Electric Current
•
An induced current may flow in only one
direction. A current that flows in only one
direction is called direct current, or
simply DC.
•
An induced current my reverse directions
very quickly over and over again. A
current that reverses direction repeatedly
is called alternating current, or simply
AC.
Induction of Electric Current
•
Batteries supply a direct current.
•
Thomas Edison used DC in his first electric
generating plant.
Induction of Electric Current
•
The electric circuits in homes, schools, and other
buildings is alternating current.
•
An advantage of AC over DC is that AC voltage can
be easily raised or lowered to a higher or lower
voltage. This means that a high voltage can be used
to send electrical energy over great distances, then
the voltage can be reduced to a safer level for
everyday use.
•
Nikola Tesla is credited for creating the AC system
we use today to distribute electricity to the entire
nation.
Generators
•
An electric generator changes mechanical
energy into electrical energy.
•
An electric generator is the opposite of an
electric motor. Remember an electric motor
changes electrical energy to mechanical
energy.
•
Generators that produce AC = AC
generators
•
Generators that produce DC = DC
generators.
Generators
•
The electric company uses giant generators to
produce energy for your home and school.
Transformers
•
Electric companies send electrical energy
through wires at high voltages. Your home,
though, uses electrical energy at low voltages.
Transformers are used to change the voltage
of an electric current.
Transformers
•
A transformer is made up of two coils of
wire, each wrapped around an iron core.
•
One coil of a transformer - called the
primary coil - is connected to an
alternating current. The other coil - called
the secondary coil - is not connected to a
source of electricity.
Transformer
Text
A Transformer at Work
•
AC flows through the primary coil of a
transformer. This causes a magnetic field
to change as the current alternates. The
changing magnetic field induces a current
in the secondary coil.
A Transformer at Work
•
A transformer can either increase or
decrease voltage. A step-up transformer
increases voltage. In a step-up
transformer, there are more loops in the
secondary coil than the primary coil.
A Transformer at Work
•
A step-down transformer decreases voltage.
In a step-down transformer, there are fewer
loops in the secondary coil than in the primary
coil.
A Transformer at Work
•
Transformers allow safe transfer of electrical
energy from generating plants to homes and
other buildings. Step-up transformers are used
to step up voltage in a current that comes out
of a power plant. Step-down transformers are
used to step down voltage before the current
is used in a home.