Title: Technological Impacts
1TEST 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.
4Review 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.
5Cotton
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
6Review 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
7Review 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
8TERMINOLOGY
- 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).
10Review Electric Schematics
- What is a schematic?
- Which of the following is a schematic?
A schematic is a diagram that represents the
elements of a system without using realistic
pictures
11Review March 04, 2010
DRILL
- What does the following schematic symbol
represent? - What does the following schematic symbol
represent? - How many volts are typical in a residential
electrical outlet? - What do graphs of DC and AC power sources look
like? Why?
DC Power Supply
AC Power Supply
120 volts
12Review 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 ?
13Review Problems Joules Law
- Write the given
- information
- V 144 Volts
- P 20,000 Watts I ?
- Rearrange, Substitute, and Solve
- 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
15Review Resistance Calculations
- Resistors in parallel add their reciprocals
R1
R2
R3
Total Resistance
1 1 1 1
R R1 R2 R3
T
16Review 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.
18Review ELECTRIC MOTORS
120 V
Lamp
19Review 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)
20Review 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.
21Review 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
22Review 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)
24Review 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.
25Review March 2, 2010
DRILL
- An electric motor converts _________ energy into
__________ energy. - 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
29Review 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
30ReviewProblems 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 ?
31Review Problems Joules Law
- Write the given
- information
- V 144 Volts
- P 20,000 Watts I ?
- Rearrange, Substitute, and Solve
- Sketch a schematic diagram of the circuit
P V x I I 20,000W / 144V R 138.9 A
I P / V
32HOMEWORK
-
- STUDY FOR TEST TOMORROW
- HAND IN REVIEW BEFORE TEST