ELECTRICITY

1
(No Transcript)
2
Basic Electricity Info...

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

3

• All matter is made up of positive and negative
  charges
• The negatives charges (electrons) can
• move freely and this movement creates
• ELECTRICITY!

4

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

5

• Most of the time, the and charges cancel each
  other out.
• Most matter is neutral

6
Static Electricity

• Static electricity is the buildup of charges on
  an object
• The word static means not moving

7

• How can electric charges build up on an object?
• Friction
• Conduction
• Induction

8

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

9
Conductors

• A conductor is a material through which electric
  charges move easily

Examples of conductors Metals such as copper,
aluminum, gold, silver
10
Insulators

• An insulator is material through which electric
  charges cannot move easily
• Examples plastic, rubber, wood, glass and sand

11
Static Discharge

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

12
Lightning!

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

13

• Only some lightning reaches Earth
• and it can be VERY dangerous and can cause
  property damage.

14

• 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

15

• The electrons collect in the lower part of the
  cloud
• They induce positive charges from the ground
  below.

16
Who is this?

• Clues
• Inventor
• Lightning rod
• Ben Franklin
• A lightning rod conducts an electric charge from
  the cloud directly to the ground.

17
Electricity Mouse and Cheese Analogy

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

18
Electricity Mouse and Cheese Analogy

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

19
The Mouse Cheese Circuit

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

20
The Mouse Cheese Battery

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

21
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

22
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

23
Electrochemical Cells

• Electricity can be generated by a chemical
  reaction
• An electrochemical cell changes chemical energy
  into electrical energy

24
Electric Current Measurement

• Each month your family receives an electric bill.
• How does Con Ed determine how much money you owe?

25

• CURRENT is the rate of flow of charges

26

• Voltage -causes current to flow through an
  electric current

27

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

28

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

29

• A wires resistance depends on
• The kind of material it is made of
• The length
• The temperature

30
What do you think are the TOP FIVE Power RATINGS
for Common Appliances?

• 1.
• 2.
• 3.
• 4.
• 5.

31
NAME this SCIENTIST!

• Who invented the light bulb?
• Thomas Edison

32

• How does a light bulb work?
• Electrons flow through a wire and heats up the
  chemicals in the filament.

33
Light Bulbs

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

34
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

35
Resistance

• The symbol for resistance is R
• Resistance is measured in units called ohms

36
Voltage

• Voltage is measured in volts
• The symbol for volt is V
• Voltage is measured with a voltmeter

37
Electroscope

• An electroscope is an instrument used to detect
  an electric charge

38
Ohms Law

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

39
Ohms Law

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

40
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?

41
Solution

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

42
Solution

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

43
Solution

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

44
Solution

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

45

• 5.) Solve for I (Current)

46
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.

47

• 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.

48

• Therefore, there is a flow of charge and
  eventually the chicken will be friedget it?

49
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?

50
Sample Problem

• Answer