ELECTRICITY

What would life be like without electricity?

List 4 things that you would miss the most:           1) ______________________________           2) ______________________________           3) ______________________________           4) ______________________________           

Positive and Negative Charge

• atoms have protons (positive) and electrons (negative);  neutrons are neutral

• when objects have an excess of electrons, they become negatively charged

Opposites attract

Objects with the same charge repel

 

Diagram of an Atom

Protons and Neutrons are in the center

Electrons orbit around the outside

      -- these are SUBatomic particles

Bohr model of the atom Label the protons, neutrons, electrons, and the nucleus

2.  What is another particle that is smaller than a subatomic particle?  (starts with the letter L)

3. What is meant by DUAL NATURE of particles?

1.  Name the six types of quarks:

Static electricity occurs when electrons transfer to your clothes or hair and give them a charge.  When you touch something, the charge is released, causing a "jolt"

Each hair is negatively charged and repels other hairs.

Or balloons stick to the cat

Electric fields surround every charge and can act upon other objects (even without touching them)

The force created by this field can either                                                attract          or           repel

Conductor - material in which electrons can flow freelyEx. Metals, such as copper

Insulator - electrons do not move easily throughEx. plastic, rubber

Lightning Gallery at

http://environment.nationalgeographic.com/environment/photos/lightning-cloud-ground/

1.  What happens when warm air collides with cold air?

2.  Humans are good conductors because they contain ___________

3.  Name one thing you can do to decrease your chances of being struck by lightning?

4.  What is a stepped leader?

What is Grounding?

Buildings often install lightning rods, which provide a path for electrons to take to the earth, bypassing the building and sensitive electric equipment

What Is Electric Current?

- net movement of electric charges (electrons) in a single direction

- measured in amperes

This diagram shows a simple LED driver circuit. When the battery is connected the positive end of the battery pulls electrons from the negative end of the battery and through the circuit. This circuit has three basic properties: voltage, current, and resistance.

What Is a Voltage Difference?

- the force that causes electrons to flow- electric charge flows from a higher voltage to a lower voltage

Circuit = a closed path that electric current follows

This flow of electrons can power things like light bulbs

Resistance = tendency for material to oppose the flow of electrons

 -- electric current loses energy as it flows-- resistance is measured in OHMS  

* Copper has a low resistance, hence it is used for household wiring and other electronics

STOP AND THINK

1. A  positively charged subatomic particle is ____        negatively charged  subatomic particle is ____

2.  Amperes are used to measure  _________

3.  A closed path that electrons (current) can flow through is a:

4.  Materials that current can flow through easily are called:

5. OHMS are used to measure the __________ of a circuit.

As the length of a wire increases, so does its resistance

As the wire becomes thinner, its resistance increases

the thin wire in a tungsten light bulb glows due to this resistance

Ohm's Law --  the current (I) in a circuit equals the voltage difference  (V) divided by resistance (R)

Quick Calculations:

1.  What is the current of a circuit with a voltage difference of 20 volts and a resistance of 10 ohms.

2.  What is the Voltage difference  in a circuit with a resistance of 11 ohms, and a current of 2 amperes. 

1.  What is the center of an atom called?2.  Electrons are attracted to _________3.  Electrons move from the ___ to the ___ side of a battery.4.  What is the most common metal used in wiring?5. How many volts are in an AA battery? ______6.  How many volts are in a wall outlet? 7. A device used to turn electricity on and off is a _______8. In which type of circuit can you turn a light off and the other will stay on?  [  series / parallel ]

CircuitsHow many electrical devices can you see in this room?  Name 2.

Circuits have:

1)  source of voltage difference (battery or outlet)2)  device that uses the energy (light)3) conductors (wires) form a closed path to device

Series Circuit

Example:  A string of christmas lights, when one light burns out, no lights will work.  Why?  Because that burned out bulb breaks the circuit to all the bulbs.  

Each bulb along the path shares the voltage, so the bulbs may appear dim.

Parallel Circuits

Series circuits aren't a good way to wire a house.  If you turned off one light, then all the lights would go out. 

Parallel circuits contain two or more branches

Disadvantage:  Even when you turn a light off, current continues to flow through the system.   

This is why you shouldn't stick a fork in an electric socket!

A switch can break a circuit

And turn a device on or off

Would this switch still work?

Identify the type of circuit:

______________________ ______________________

What is a fuse?

Fuses contain a tiny piece of metal that melts if the current gets too high - this breaks the circuit.

Too many appliances on in one room can overload the circuit and blow a fuse.

Where does electricity come from?

Most electricity comes from converting heat energy into electrical energy - burning fossil fuels such as coal and natural gas.

Some electricity is generated from dams, and nuclear reactors

How do dams generate electricity?

As water flows through the dam it spins turbines, which will create electricity.

These are referred to as:

HYDROELECTRIC DAMS

How are dams built?

How do they hold all that water back?

What happens when dams fail?

Cost of Electricity1)  Most companies charge by the amount of energy used2)  This is measured in kilowatt hours (kWh)3)  Each light bulb in your house costs money to leave on!

4)  Meters outside your house measure how much energy is used

Check out:http://www.energyeducation.tx.gov/

What is the difference between alternating current and direct current?

Check out  

http://www.pbs.org/wgbh/amex/edison/sfeature/acdc.htmlhttp://www.pbs.org/wgbh/amex/edison/sfeature/acdc.html

AC =  alternating currentDC = direct current

Direct Current is found in simple circuits like a battery powered flashlight.

Alternating Current  The direction of current flowing in a circuit is constantly being reversed back and forth. This is done with any type of AC current/voltage source. AC power is used in homes and business.  It's cheaper and easier to make devices for AC power, and you can easily increase and decrease the current.

QUIZ TIME

1.  What happens when an object has an excess number of electrons?

2.  Name something that is a conductor:

3.  What unit is electric current measured in?

4.  What unit is electric energy measured in (think power bill)?

5.  The force that causes electrons to flow is the ____________ difference.

6. Is the image showing a parallel or series circuit?

7.  Where does the electricity come from that powers your house?

8.  What causes a fuse to be blown?

9.  _________ Law can be used to calculate voltage.

10.  Resistance is the tendency for  ____________ to oppose the flow of  ____________.