Electric CurrentYou Light Up My Life

SC StandardsPS 6-10

Compare alternating current (AC) and direct current (DC) in terms of the production of electricity and the direction of current flow.

PS 6-11Explain the relationship of magnetism to the movement of electric charges in electromagnets, simple motors, and generators.

Fe = K q1q2

d2 K- Coulomb’s Constant

q- charge

d- distance

Static vs Current Electricity

Static electricity – Not moving (build up of charges)

Electric current – Moving (flow of electrons through a conductor)

Why can’t you run appliances on static electricity?

Appliances need a steady flow of electricity.

Types of Current

Two Types of Electric Current

1. Direct Current –always flows in the SAME direction: from negative to positiveAnything that runs off of a chemical cell or a BATTERY uses DIRECT Current

Two types of Electric Current2. Alternating Current–

Constantly changes direction of electron flow: electrons jiggle back and forth as they are pushed down the wireAnything that plugs into a wall socket uses alternating current

Alternating Current Produced:

Alternating Current can be produced by a generator.

The generator terminals alternate between negative and positive. Electrons are repelled and attracted, but since the terminals are continually flipping, the current jiggles back and forth.

Moving Charges and Magnetic Fields

Electric current (moving electrical charges) produces a magnetic field.The magnetic field is generated in counterclockwise circles around the direction of the moving electrons.

The stronger the current flowing through the wire, the stronger the magnetic field

Electromagnets

Temporary magnet made by placing a piece of iron inside a current-carrying coil of wire

The more turns of wire the greater the strength of the magnet

The larger the current the greater the strength of the magnet

The bigger the Iron core the greater the strength of the magnet

Where can I find electromagnets? (Just to name a few!)

Stereo speakersElectric motorsGenerators (electric power plants)VCR’sTape decksComputer hard drives

Electric MotorsElectric motor – device which turns electrical energy into mechanical energy through the use of an electromagnet

How do they work?

1. Charge from battery makes coil become magnetized

2. The North end of coil lines up with South end of magnet

3. Charge direction in the coil is flipped which flips the north – south ends of the coil so the coil rotates to line up with magnet again

4. This happens repeatedly to keep the coil rotating in the magnet

GeneratorsGenerator – a device that turns mechanical energy into electrical energy using an electromagnet

Generators

Generator – similar to electric motor

How do generators work?1. Some source of

mechanical energy turns a coil which is sitting in a permanent magnet.

How do generators work?

2. As the coil rotates in the magnetic field it generates electricity. This is called electromagnetic induction.

How do generators work?3. Generators produce

AC current.

Generating Electricity for your Home

Electromagnets are turned by a turbine – a huge wheel that rotates when pushed by water, wind, or steam.

TransformersTransformersTransformer – a device that alters the voltage of an alternating current

Two coils of wire wrapped around the same iron core

A step up transformer is used when the electricity leaves the power plant to boost its voltage so less energy is lost as heat as it travels through the power linesBefore the electricity enters your house a step down transformer is used to lower the voltage to the standard 120V

That’s All Folks!