Transcript Bellringer - Madison County Schools

Bellringer
What is one way to increase the strength of
the magnetic field of a current?
Electricity from
Magnetism
Notes
Induction of Electric
• Motion can produce
electrical energy.
Current
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.