Basic Electricity Info...

All electricity is energy that results from the movement of electrons.

All matter is made up of positive and negative charges

The negatives charges (electrons) can

move freely and this movement creates…

ELECTRICITY!

Electric current is the movement or flow of electrons. CIRCUIT is the PATH the electricity travels on.

•Most of the time, the + and – charges cancel each other out.

•Most matter is neutral

                              

Static Electricity

•Static electricity is the buildup of charges on an object

•The word static means not moving

How can electric charges build up on an object?

•Friction•Conduction•Induction

When charges on an object are rearranged without physical contact, it has been charged by induction.

Conductors• A conductor is a material

through which electric charges move easily

Examples of conductors:

Metals such as copper, aluminum, gold, silver

Insulators

•

• An insulator is material through which electric charges cannot move easily

• Examples: plastic, rubber, wood, glass and sand

Static Discharge

The loss of static electricity as charges move off an object is called static discharge

Lightning!Lightning!

A giant electric spark, called lightning, is the result of static discharge created in a cloud.

How is lightning formed?

• The wind rubs together the water molecules and particles of matter in the clouds

• This friction causes static electricity to build up in the cloud

• The electrons collect in the lower part of the cloud

• They induce positive charges from the ground below.

Only some lightning reaches Earth

and it can be VERY dangerous and can cause property damage.

Who is this?Who is this?

• Clues:• Inventor• Lightning rod• Ben Franklin• A lightning rod

conducts an electric charge from the cloud directly to the ground.

Electricity ~ Mouse and Cheese Analogy

The negative charges (mice) will do work in order to get to the positive charges (cheese).

Electricity ~ Mouse and

Cheese Analogy

•The mouse wants to get to the cheese, but there is no path.

The Mouse Cheese Circuit

•

•The mouse (electron) will gladly do work to get to the cheese (proton)

Electrochemical Cells

• Electricity can be generated by a chemical reaction

• An electrochemical cell changes chemical energy into electrical energy

The Mouse Cheese Battery

• Both the D cell and the AA cell produce 1.5 volts.

• What is the difference?

• Answer: The D cell will last longer

The Mouse Cheese Battery

• This is the mouse-cheese version of a D cell and an AA cell

• Which is which?

Real Batteries

• Both the D cell and the AA cell produce 1.5 volts.

• What is the difference?

• Answer: The D cell will last longer

Electric Current Measurement

• Each month your family receives an electric bill.

• How does Con Ed determine how much money you owe?

CURRENT ~ is the rate of flow of charges

                                          

VOLTAGE ~ The amount of work that each charge will do as it goes through the circuit.

RESISTANCE ~ the opposition to the flow of charge. Any appliance that asks the charge -- to do work will slow the charge down

A wire’s resistance depends on:

• The kind of material it is made of

• The length and width• The temperature (what it is

insulated with)

What do you think are the TOP FIVE Power RATINGS for

Common Appliances?1.2.3.4.5.

You are given four outlets to plug in 4 separate electrical appliances. You may only use these 4 appliances for an entire week.

What 4 would you choose?

NAME this SCIENTIST!NAME this SCIENTIST!

Who invented the light bulb?

Thomas Edison

How does a light bulb work?

Electrons flow through a wire and heats up the chemicals in the filament.

Light BulbsWhen the

electrons reach the filament, its resistance is so great that the electric energy is converted into heat and light energy.

Current•The symbol for

current is the capital letter I

•The unit measure for current is amperes or amps

•Current is measured with an ammeter

Resistance

•The symbol for resistance is R

•Resistance is measured in units called ohms

Voltage

• Voltage is measured in volts

• The symbol for volt is V

• Voltage is measured with a voltmeter

Electroscope

An electroscope is an instrument used to detect an electric charge

Ohm’s Law

• Ohm’s Law states that the current in a circuit is equal to the voltage divided by the resistance

Ohm’s Law

• Where:  V is the Voltage measured in volts  I is the Current measured in amperes  R is the resistance measured in Ohms 

Sample Problem

• A nine volt battery supplies power to a cordless curling iron with a resistance of 18 ohms. How much current is flowing through the curling iron?

Solution

• 1.) Since V(Voltage) and R(Resistance) are known, solve for I(Current) by dividing both sides of the equation by R.

Solution

2. The R's on the right hand side of the equation cancel.

Solution

• 3.) I is then left in terms of V and R

Solution

• 4.) Substitute in the values for V(Voltage) and R(Resistance).

5.) Solve for I (Current)

Why can a bird sit on a power line?

When a bird sits on a power line, both feet are on the line.

There is no potential difference between the feet.

If one leg is on the ground and the other one is on the power line, then there are potential difference between these two legs.

Therefore, there is a flow of charge and eventually the chicken will be fried…get it?

Sample Problem

• A 110 volt wall outlet supplies power to a strobe light with a resistance of 2200 ohms. How much current is flowing through the strobe light?

Sample Problem

• Answer:

•