Technological Impacts

1
TEST REVIEW ELECTRONS

• Electricity begins with Electrons.

• ATOMS
• Electron cloud surrounds an atoms nucleus
• Nucleus is made of
• Electrons negative charge
• Protons positive charge
• Neutrons zero charge (neutral)

Protons and Neutrons
2
REVIEW CIRCUITS

• The paths that electrons travel are called
  circuits.
• Circuits must consist of three things

ELECTRONS move from negative ( - ) terminal
to positive ( ) terminal

• Power Source with positive and negative
  terminals.
• Conductor the path the electrons travel along.
• Load this is what the electricity powers (e.g.
  motor, light bulb)

3
REVIEW CONDUCTORS

• Conduct from Latin for leading, guiding.
• A conductor is any material that allows electrons
  to easily flow.
• Remember the atom
• Conductors electrons are not tightly bound to
  the atom.
• Conductors have free electrons.
• Which material has free electrons, Wood or Metal?
• Metals conduct electricity easily.

4
Review INSULATORS

• Insulate from Latin for separate, divided.
• An insulator is any material that impedes the
  flow of electrons.
• Remember the atom
• Insulators electrons are tightly bound to the
  atom.
• Because the electrons dont move, insulators
  cannot conduct electricity very well, if at all.
• Which material has bound electrons, Wood or
  Metal?
• Wood does not have free electrons.

5
Cotton
Bound Electrons
Gold
Wood
Plastic
Silver
Aluminum
Air
Copper
Free-electrons
INSULATOR Cotton Wood Plastic Air BOUND
ELECTRONS
CONDUCTOR Copper Gold Silver Aluminum FREE
ELECTRONS
6
Review Joules Law

• James Joule (1818 1889) showed that heat and
  electrical energy are interchangeable.
• Joules Law
• Power Voltage x Current
• P V I
• Watts Volts x Amperes

7
Review Ohms Law

• George Ohm (1789 1854) a high school and
  university mathematics instructor
• Discovered 1827
• Voltage Current x Resistance
• V I R
• What are the units of this formula?
• Volts Amperes x Ohms

8
TERMINOLOGY

• Current (I) the motion of electrons from one
  atom to the next in a material.
• In our circuit, electrons flow from ___________
  terminal to the ___________terminal.
• This motion of electrons through our conductor
  (wire) is considered current (like water through
  a pipe).
• Materials that resist current are
• called ___________.
• Materials that provide
• a path for current are called
• ___________.
• Current is measured in AMPERES (Amps)

NEGATIVE
POSITIVE


INSULATORS

CONDUCTORS

9
Review TERMINOLOGY

• Voltage (V) the electric potential between two
  points of opposite charge.
• Voltage is the potential energy of the electrical
  power source.
• Voltage is measured in Volts (V).

10
Review Electric Schematics

1. What is a schematic?
2. Which of the following is a schematic?

A schematic is a diagram that represents the
elements of a system without using realistic
pictures
11
Review March 04, 2010
DRILL

1. What does the following schematic symbol
   represent?
2. What does the following schematic symbol
   represent?
3. How many volts are typical in a residential
   electrical outlet?
4. What do graphs of DC and AC power sources look
   like? Why?

DC Power Supply
AC Power Supply
120 volts
12
Review Problems Joules Law

• Write the given information
• V 144 Volts
• P 20,000 Watts I ?
• Sketch a schematic diagram of the circuit
• Start with power source
• Add conductors
• Add load
• Add current

P 20,000 W
V 144V
-
I ?
13
Review Problems Joules Law

• Write the given
• information
• V 144 Volts
• P 20,000 Watts I ?
• Rearrange, Substitute, and Solve

1. Sketch a schematic diagram of the circuit

P V x I I 20,000W / 144V R 138.9 A
I P / V
14
Review Resistance Calculations

• Resistors in series are added

R1
R2
R3
Total Resistance
R R1 R2 R3
T
15
Review Resistance Calculations

• Resistors in parallel add their reciprocals

R1
R2
R3
Total Resistance
1 1 1 1

R R1 R2 R3
T
16
Review ELECTRIC MOTORS
What is a schematic? How would a schematic
which includes an electric motor look?
A schematic is a diagram that represents the
elements of a system without using realistic
pictures.
Switch Commutator
Motor
V 9V
I
17
Review ELECTRIC MOTORS

• Now that you know what switches look like in
  electrical schematics, draw an electrical
  schematic for a lamp plugged into a wall outlet.
• Remember that AC power supplies look like
  in electrical schematics.

18
Review ELECTRIC MOTORS
120 V
Lamp
19
Review TERMINOLOGY

• Resistance (R) a measure of the degree to which
  an object opposes an electric current through it
  .
• Resisting an electric current often generates
  heat.
• This is the principle behind how light bulbs
  work.
• Resistance is measured in Ohms (W the Greek
  letter Omega)

20
Review Electric Motors

• Michael Faraday (1791-1867)
• London, England.
• Physicist and Chemist
• First person to successfully create an electric
  motor.
• Discovered that electric currents create a
  magnetic field, and vice versa.

21
Review ELECTRIC MOTORS

• Electric motors are used everyday in many ways.
• A motors purpose is to turn electrical energy
  into mechanical energy.
• Motors work on simple principles of magnetism
• Opposite poles _____________
• Like poles _____________

ATTRACT
REPEL
22
Review Direct Current

• If voltage is constantly 1.5 V, what does its
  graph over time look like?

1.5 V
Voltage (volts)
1 2 3
0 2 4 6 8 10 12 14
Time (seconds)
23
Review Alternating Current

• If voltage is alternating 120 V to -120 V, what
  does its graph over time look like?

/-120 V
Voltage (volts)
-120 0 120
0 2 4 6 8 10 12 14
Time (seconds)
24
Review Electrical Technology

• Electricity can be used in a thousand different
  ways. For example
• Electric motors turn electricity into motion.
• Light bulbs, fluorescent lamps and LEDs turn
  electricity into light.
• Computers turn electricity into information.
• Telephones turn electricity into communication.
• TVs turn electricity into moving pictures.
• Speakers turn electricity into sound waves.
• Stun guns turn electricity into pain.
• Toasters, hair dryers and space heaters turn
  electricity into heat.
• Radios turn electricity into electromagnetic
  waves that can travel millions of miles.
• X-ray machines turn electricity into X-rays.

25
Review March 2, 2010
DRILL

1. An electric motor converts _________ energy into
   __________ energy.
2. List 4 household objects that use electric motors.

ELECTRICAL
MECHANICAL
Fans Pumps Garbage disposer Refrigerators Prin
ters Microwave trays Washing machines DVD
players Vacuums VCRs
ALMOST EVERY MECHANICAL MOVEMENT IN YOUR HOUSE
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28
Review Problems Joules Law
Complete problem 5 on your worksheet
29
Review Problems Joules Law

• A Lexus RX 100h hybrid has a 144 Volt battery
  system in its trunk. The electric motor that the
  batteries power can generate 20,000 Watts of
  power. Sketch a schematic diagram of this
  circuit. What is the current traveling through
  this high voltage circuit?
• Write the given information
• V 144 volts
• P 20,000 watts
• I ?

A schematic is a diagram that represents the
elements of a system without using realistic
pictures
30
ReviewProblems Joules Law

• Write the given information
• V 144 Volts
• P 20,000 Watts I ?
• Sketch a schematic diagram of the circuit
• Start with power source
• Add conductors
• Add load
• Add current

P 20,000 W
V 144V
-
I ?
31
Review Problems Joules Law

• Write the given
• information
• V 144 Volts
• P 20,000 Watts I ?
• Rearrange, Substitute, and Solve

1. Sketch a schematic diagram of the circuit

P V x I I 20,000W / 144V R 138.9 A
I P / V
32
HOMEWORK

• STUDY FOR TEST TOMORROW
• HAND IN REVIEW BEFORE TEST