#### 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.
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.
```