Electricity

1
Electricity
FOPS UNIT 4
1
2
Mini Objectives 1. Describe how objects become
electrically charged. 2. Explain how an electric
charge affects other electric charges. 3.
Distinguish between electric conductors and
insulators. 4. Describe how electric discharges
like lightening occur. 5. Relate  voltage to the
electrical energy carried by an electrical
current. 6. Describe a battery and how it
produces an electric current. 7. Explain
electrical resistance. 8. Explain how voltage,
current, and resistance are related in an
electric current. 9. Investigate the difference
between series and parallel circuits. 10.
Determine the electric power used in a
circuit. 11. Describe how to avoid dangerous
electric shock.
3
Vocabulary Electric Charge Ion Static
Charge Electric Force Electric Field
Insulator Conductor Electric Discharge Electric
Current
Circuit Voltage Resistance Ohm's Law Series
Circuit Parallel Circuit Electric Power Amperes
Introduction to Electricity VIDEO
4
What is electricity? Electricity is the flow of
electons or negative charges. It is both a basic
part of nature and one of our most widely used
forms of energy. Electricity is actually a
secondary energy source, also referred to as an
energy carrier. That means that we get
electricity from the conversion of other sources
of energy, such as coal, nuclear, or solar
energy. These are called primary sources. The
energy sources we use to make electricity can be
renewable or non-renewable, but electricity
itself is neither renewable or nonrenewable.
How Americans use electricity
5
Electricity

• Protons and Electrons have positive and negative
  charge
• Atom becomes if it loses electrons, and if it
  gains electrons then they are called ions

6
Electrons Move in Solids

• e- can move from atom to atom by rubbing
• Ex. Rubbing a balloon on hair
• Hair holds e- more loosely, so they go to the
  balloon, hair becomes , balloon becomes
• Causes static charge- imbalance of electric charge

7
QUESTION
8
Removing Static Electricity at the Gas station

• VIDEO
• Do you know what to do when pumping
  gas?

9
Ions Move in Solution

• Movement of charge can be caused by movement of
  ions
• NaCl dissolved in water Na and Cl- move freely
• Play important role in human body (Nerve cell)

10
Movement of ions through a nerve cell also called
physiology of a nerve
11
Electric Force

• Attractive or repulsive force that all charged
  objects exert on each other
• opposites attract and like repel
• depends on distance and amount of charge
• Electric Fields- surrounds every electric charge
  and exerts forces on other electric charges

12
(No Transcript)
13
(No Transcript)
14
Insulators and Conductors

• Insulator- e- cant move freely
• Ex. Plastic, wood, glass, rubber
• Conductor- e- can move easily
• Ex. Copper, gold, aluminum
• Metals are best because e- are loosely attached

15
Induced Charge

• Rubbing feet across floor collects e- from
  carpet, spread over body as you go to touch metal
  (door knob), e- in your hand move to the metal,
  you feel an electric discharge

16
Grounding

• Electrical discharge can cause damage and injury.
• i. Lightening
• ii. Even small amt. can damage circuits
• One way to avoid this is to direct that current
  into the ground called grounding.
• Examples include lightening rods, 3rd prong on
  a plug

17
(No Transcript)
18
(No Transcript)
19
Electric Shock
20
Lightening Strikes!!

• VIDEO
• Do you know what to do in a storm?
• How do people die from lightening?

21
Van der graff Generator
VIDEO
22
(No Transcript)
23
Electric Current

• Vocabulary
• Electric current Voltage
• Circuit Resistance

24
Flow of Charge

• Electric Current- flow of electric charge
• Liquids ? ions
• Solids ? electrons
• Measured in amperes (A)

Andre-Marie Ampere
25
Model for Electric Circuit

• Circuit- closed conducting loop that electric
  charge flows.

26
Series Circuits

• Series Circuit- has only one path for electric
  current to follow.
• electrical devices are connected along the same
  current path.

27
Parallel Circuit

• A circuit that has more than 1 path for electric
  current to flow.
• If one path is broken, electrons continue to flow
  through the other paths.
• resistance in each branch can be different,
  depending on the devices in the branch.

28
Schematics
Schematics of circuits are always shown in
technical manuals and other materials including
textbooks. The diagram below compares the
pictorial diagram or real world representation of
the circuit you built in Exploration 1 with the
schematic, or physics representation, of the same
circuit.
29
To be able to read or draw a schematic you will
need knowledge of what symbols are used to
represent the various elements in an electric
circuit. These symbols are fairly universal a
schematic drawn in Asia will look the same as a
schematic drawn in the US, as long as the
circuits are the same. The table below shows some
of the basic schematic symbols used in this
module.
30
Voltage

• voltage- of a battery is a measure of how much
  electrical potential energy each electron can
  gain.
• Measured in volts (V)
• As voltage increases, more electrical potential
  energy is available
  to be transformed into other
  forms of
  energy.

31
Batteries
32
Batteries

• battery supplies energy to an electric circuit.
• alkaline battery two terminals are separated by a
  moist paste.

33
Why do batteries die?
34
Battery Life

• Battery contains limited amt. of chemical.
• Reaction change chemicals into new compounds.
• When chemicals used up battery is dead

35
Resistance

• measure of how difficult it is for electrons to
  flow through a material.
• unit of resistance is the ohm (?).
• Insulators generally have much higher resistance
  than conductors

36
Buildings Use Copper Wires

• Copper has low resistance and is one of the best
  electric conductors.
• Less heat is produced as electric current flows
  in copper wires, compared other materials.

37
Resistance of Wires

• Depends on length, thickness, material.
• Increases longer, thinner

38
Resistance at work
39
Light bulb Filaments

• filament is made of wire so narrow that it has a
  high resistance.
• electric current flows in the filament, it
  becomes hot enough to emit light.
• made of tungsten metal (high melting pt)

40
Electric Circuits

• Vocabulary
• Ohms Law Series Circuit
• Parallel Circuit Electric Power

41
Controlling the Current

• Amount of current depends on
• voltage supplied by the battery
• resistance of the conductor

Bucket height is like voltage ? higher up more
volts
Hose is like resistance ? longer and thinner
more resistance
42
Ohms Law

• Voltage (v) current (amps) x resistance (omhs)

• If voltage in a circuit increases the current
  increases.

• When the resistance is increased the circuit
  decreases

43
Ohms Law example

• A lightbulb is plugged into a wall outlet. If the
  lightbulb has a resistance of 220O and the
  current is 0.5 A, what is the voltage of the
  outlet?

Current I 0.5 A Resistance R 220O
V IR (0.5 A) (220O) 110V
44
Practice

• An electric iron plugged into a wall has a
  resistance of 24O. If the current in the iron is
  5.0 A, what is the voltage provided by the wall
  socket?
• What is the current in a flashlight bulb with a
  resistance of 30 O if the voltage of the
  batteries is 3.0 V?
• What is the resistance of a bulb connected to a
  110 V wall outlet if the current in the bulb is
  1.0 A?

120 V
0.1 A
110 O
45
Protecting Electric Circuits

• In a parallel circuit, current increases as more
  devices are added ? wire heats up.
• To keep the wire from becoming hot enough to
  cause a fire, the circuits in houses and other
  buildings have fuses or circuit breakers.

46
Protecting Electric Circuits
47
Electric Power

• Rate at which electrical energy is converted into
  other forms of energy
• SI unit of power is the watt.

Power (watts) Current (amps) x Voltage (volts)
48
Practice

• A lightbulb is plugged into a 110 V wall outlet.
  How much electric power does the lightbulb use if
  the current in the bulb is 0.55 A?

Voltage V 110 V Current I 0.55 A
P IV (0.55 A) (110 V) 60 W
49
Practice

• The batteries in a portable CD player provide 6.0
  V. If the current in the CD player is 0.5 A, how
  much power does the CD player use?
• What is the current in a toaster uses 1,100 W of
  power when plugged into a 110 V wall outlet?
• An electric clothes dryer uses 4,400 W of
  electric power. If the current in the dryer is
  20.0 A, what is the voltage?

3.0 W
10 A
220 V
50
(No Transcript)
51
Cost of Electric Power

• sell it in units of kilowatt-hours, amount of
  electrical energy equal to using 1 kW of power
  continuously for 1 h.

52
The End