BellringerWhat is one way to increase the strength of the

magnetic field of a current?

Electricity from

MagnetismNotes

• 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

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.

TextTransformerTransformer

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.