ELECTRICITY

What is Electricity?

Watch the Bill Nye Video and answer the corresponding questions.

Questions Video # 1 1. What is electricity?

2. What is an electrical circuit?

3. How does electricity make a bumper

car go? 4. Give an example of an electrical

circuit.

5. Where does electricity come from?

The Basics of Electricity

All atoms in matter always contain electrical charges. ( Positive and Negative)

Electric Charge – a form of charge, either positive or negative, that exerts an electric force.

When objects of different materials are rubbed together they become “charged” with electricity.

Static Electricity

A build up of electric charge on the surface of an object.

When clothes are in the dryer, many times the electric charge remains “static.” This means that the charge stays where the rubbing action occurred on each of the charged objects.

* This is why we use Bounce sheets in the dryer.

How do anti static sheets work?

These sheets act as a lubricant of sort for your clothes.

You cannot eliminate these electrical charges completely but you can minimize them.

Companies put in a waxy compound in sheets of Bounce or Cling Free and liberated by the dryer's heat.

The Law of Electric Charges

Two objects with like charges, whether positive or negative, always repel one another.

When a positively charged object is near a negatively charged object, they attract one another.

Law: “Like charges repel another, and unlike charges attract one another.”

http://www.youtube.com/watch?v=iRnZNq_6ijI

Static Electricity

http://phet.colorado.edu/simulations/sims.php?sim=Balloons_and_Static_Electricity

http://phet.colorado.edu/simulations/sims.php?sim=John_Travoltage

How do we know if an object is positively charged or negatively

charged?

In order to tell this, we must observe the object that is being repelled by an object with a known charge.

Charged objects will attract both neutral and objects with unlike charges.

Charged objects will only repel objects with like charges.

Charging by Friction

The transfer of electrons between 2 neutral objects (made of different materials) that occurs when they are rubbed together.

Bill Nye Video Part 2:

Electricity from Friction

The effects of static electricity occur only when electric charges shift from their normal position on a neutral object or are transferred from one object to another.

There are three ways that objects become electrically charged: by Friction, by Contact and by Induction.

Electrostatic Series

Material Hold on Electronsacetate weakglasswoolcat's fur, human haircalcium, magnesium, leadsilkaluminum, zinccotton Increasing tendency to gain electronsparaffin waxebonitepolyethylene (plastic)carbon, copper, nickelrubbersulphurplatinum, gold Strong

Video: Transferring Charge

http://www.youtube.com/watch?v=IdcPeW1XwKs

http://www.youtube.com/watch?v=gct1BmKNvU0&feature=related

Door Knob experience

Insulators and Conductors

Electrical Insulator - a substance where electrons cannot move freely from atom to atom.

Electrical Conductor – a substance where electrons can move freely from atom to atom.

Good Insulators

Oil Rubber Plastic Wax

These objects hold electrical charge and build up static charge better than conductors, however even though they hold static electricity , they can protect us from electric shock

Good Conductors

Silver Copper Aluminum Iron Gold

Because the electricity is transferred as soon as it is produced, there is no build up of static electricity.

Static Electricity in Winter

Why is static electricity more evident in the winter months??

Less water vapour in the air, or the air is dryer which means that it is an insulator and does not easily pick up charges from our body and therefore creates a static build up.

Grounding

When a charged object is connected, or grounded, to Earth, it shares its charge with the entire Earth.

This means that the charge is removed or spread out over a larger surface.

Induction

Induction occurs without direct contact of an object.

Remember: charging by friction and charging by contact occurs only when the objects rub against or touch one another.

How Induction Works

When an uncharged object, such as a dust particle, is charged by induction, the nearby charged object doesn’t actually touch the dust particle at all.

A computer screen or television screen becomes charged when it is turned on.

When a dust particle is near a television screen, the charges on the screen cause (induce) the electrons on the dust to change position.

This causes the dust particles to have an opposite charge than the charge on the television screen.

Lightning

About 2000 thunderstorms are occurring throughout the world at any given time, creating 100 lightning strikes every second, or about 8 million strikes daily.

Lightning involves exchanging electric charges between the atmosphere and the Earth.

Electric charges are constantly being removed from the Earth’s surface by different processes.

Ex. Evaporation of water molecules, exhaust gases.

Lightning

When thunderclouds form, huge numbers of negative charges concentrate near the bottom of the cloud.

When the negative charge at the base of the cloud moves over tall objects, such as a building, it is sometimes close enough to return the ground in a huge spark, called lightning.

The jagged path that lighting has is caused by the electric charges moving along the path of least resistance in the air.

Lightning

Lighting tends to hit taller objects because the taller objects shortens the path to the ground, especially if they are metal conductors.

Why are you safe in a car during lightning storms? Rubber tires aren't why you're safe in a car during a

lightning storm. In strong electric fields, rubber tires actually become more conductive than insulating. You're safe in a car because the lightning will travel around the surface of the vehicle and then go to ground.

Lightning Video

http://www.youtube.com/watch?v=h7c6z_3dLE4

Bill Nye Video

http://www.youtube.com/watch?v=BXS2XwwH_uA

http://www.youtube.com/watch?v=919TBO7G3yI&feature=related