TEST REVIEW ELECTRONS Electricity begins with Electrons. ATOMS U3e-L1 TEST REVIEW ELECTRONS Electricity begins with Electrons. ATOMS Electron cloud surrounds an atom’s nucleus Nucleus is made of Electrons – negative charge Protons – positive charge Neutrons – zero charge (neutral) Protons and Neutrons

ELECTRONS move from negative ( - ) terminal to positive ( + ) terminal U3e-L1 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) LOAD

REVIEW CONDUCTORS Which material has free electrons, Wood or Metal? U3e-L1 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.

Review INSULATORS Insulate – from Latin for “separate, divided.” U3e-L1 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 don’t move, insulators cannot conduct electricity very well, if at all. Which material has bound electrons, Wood or Metal? Wood does not have free electrons.

Air Copper Free-electrons Cotton Aluminum Bound Electrons Silver Gold U3e-L1 Air Copper Free-electrons Cotton Aluminum Bound Electrons Silver Gold Wood Plastic INSULATOR Cotton Wood Plastic Air BOUND ELECTRONS CONDUCTOR Copper Gold Silver Aluminum FREE ELECTRONS

U3e-L1 Review Joule’s Law James Joule (1818 – 1889) – showed that heat and electrical energy are interchangeable. Joule’s Law: Power = Voltage x Current P = V I Watts = Volts x Amperes

U3e-L1 Review Ohm’s 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

U3e-L2 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 LOAD INSULATORS CONDUCTORS

U3e-L2 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).

Review Electric Schematics U3e-L3 Review 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

U3e-L8 Review March 04, 2010 DRILL 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

Review Problems – Joule’s Law U3e-L2 Review Problems – Joule’s 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 = ?

Review Problems – Joule’s Law U3e-L2 Review Problems – Joule’s Law Write the given information: V = 144 Volts P = 20,000 Watts I = ? Rearrange, Substitute, and Solve Sketch a schematic diagram of the circuit: V = 5V I = .7A - + R = ? P = V x I I = 20,000W / 144V R = 138.9 A I = P / V

Review Resistance Calculations U3e-L3 Review Resistance Calculations Resistors in series are added: R1 R2 R3 Total Resistance: R = R1 + R2 + R3 T

Review Resistance Calculations U3e-L3 Review Resistance Calculations Resistors in parallel: add their reciprocals R1 R2 R3 Total Resistance: 1 1 1 1 = R R1 + R2 + R3 T

Review ELECTRIC MOTORS U3e-L8 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

Review ELECTRIC MOTORS U3e-L8 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.

Review ELECTRIC MOTORS U3e-L8 Review ELECTRIC MOTORS 120 V Lamp

U3e-L2 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)

Review Electric Motors U3e-L8 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.

Review ELECTRIC MOTORS U3e-L8 Review ELECTRIC MOTORS Electric motors are used everyday in many ways. A motor’s purpose is to turn electrical energy into mechanical energy. Motors work on simple principles of magnetism: Opposite poles _____________ Like poles _____________ ATTRACT REPEL N S N S N S

U3e-L8 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)

Review Alternating Current U3e-L8 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)

Review Electrical Technology U3e-L1 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.

An electric motor converts _________ energy into __________ energy. U3e-L6 Review 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 Printers Microwave trays Washing machines DVD players Vacuums VCRs ALMOST EVERY MECHANICAL MOVEMENT IN YOUR HOUSE

U3e-L6

U3e-L6

Complete problem #5 on your worksheet U3e-L2 Review Problems – Joule’s Law Complete problem #5 on your worksheet

Review Problems – Joule’s Law U3e-L2 Review Problems – Joule’s 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

ReviewProblems – Joule’s Law U3e-L2 ReviewProblems – Joule’s 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 = ?

Review Problems – Joule’s Law U3e-L2 Review Problems – Joule’s Law Write the given information: V = 144 Volts P = 20,000 Watts I = ? Rearrange, Substitute, and Solve Sketch a schematic diagram of the circuit: V = 5V I = .7A - + R = ? P = V x I I = 20,000W / 144V R = 138.9 A I = P / V

STUDY FOR TEST TOMORROW HAND IN REVIEW BEFORE TEST U3e-L2 HOMEWORK STUDY FOR TEST TOMORROW HAND IN REVIEW BEFORE TEST