1. Electricity

2. 3.01 – Electrical Charges What is a Charge?
• Remember the structure of the atom

3. 3.01 – Electrical Charges • Remember the structure of the atom
– Protons are positive
– Neutrons are neutral
– Electrons are negative
• Protons and neutrons in the nucleus (center)
• Electrons in the electron cloud
• Protons and neutrons have about the same mass.
• Electrons are smaller mass.

4. 3.01 – Electrical Charges
When we charge something, we transfer electrons
Electrons are not created or destroyed
Ions are atoms with a charge (uneven number of electrons and protons.
• Neutral atom = protons =electrons
• Positive ion - protons > electrons
• Negative ion – protons< electrons

5. 3.01 – Electrical Charges
The movement of the electrons from one atom to another leads to an electric charge.
• Remember that the pictures below using models to represent the exchange of an electron to form ions. These models do not give a detailed picture of the arrangement of electrons within an atom.

6. 3.01 – Electrical Charges • Charges Exert Forces • Like charges repel
• Opposite charges attract
• Force of charge depends on
– Amount of charge
– Distance between charges

7. 3.01 – Electrical Charges
• Electric Field-

8. 3.01 – Electrical Charges • Charging by Contact – Objects must touch
• Charging by Induction
– Objects do not have to touch, just be near each other

9. 3.01 – Electrical Charges • Lightning
– Thunder – sound produced by the lightning
– Grounding

10. 3.01 – Electrical Charges
• Some materials are better at transferring or accepting electrons
– Conductors – good at transferring electrons
– Insulators – poor at transferring electrons

11. 3.01 – Electrical Charges • Semiconductors
• Have both insulator and conductor properties
• Doping – chemical process of adding impurity to pure element; changes the elements ability to conduct an electric charge.

12. Electric Current
• Electric Current is the rate of flow of electrons
• Electrons flow in a way similar to water
• The rate if flow of electrons is measured in ampere (amps)

13. 3.02 - Electric Current • Why does current flow??
• Electrons will flow in a wire only when there is a difference in electrical pressure
• Voltage is the amount of pressure behind electron flow
• Voltage is directly proportional to electrical pressure
• Voltage = potential energy/charge

14. 3.02 - Electric Current • Electric circuits –
• Current and electron flow
– Current is in the direction of positive charge flow
– Electron flow is negative charges moving
– Current and electron flow will be in opposite directions

15. Electric Current
Faucet Analogy

16. 3.02 - Electric Current • Electrical resistance –
• Factors that affect resistance
– Length of wires
– Kind of material
– Temperature
• Resistance is measured in ohms

17. Electric Current
• Ohm’s Law - relationship between current, voltage, and resistance
• Current is directly proportional to voltage
• Current is inversely proportional to resistance
• Current(amp) = voltage(volts)/resistance(ohms)

18. Let’s Practice!!!!
How much current is in a circuit that includes a 9-volt battery and a bulb with a resistance of 3 ohms?
• How much current is in a circuit that includes a 9-volt battery and a bulb with a resistance of 12 ohms?
• What is the voltage of a circuit with 15 amps of current and toaster with 8 ohms of resistance?
• How many ohms of resistance must be present in a circuit that has 120 volts and a current of 10 amps?

19. 3.02 - Electric Current • Calculating Power
• Moving charges can do work
• Power is defined as
voltage (v) x I (amps) = Power (watts)

20. 3.02 - Electric Current Calculating Power
What is the current in a 120V circuit if the resistance 20Ω?

21. 3.02 - Electric Current Calculating Power
What is the current in a 120V circuit if the resistance 5Ω?

22. 3.02 - Electric Current Calculating Power
What voltage is required to move 2A through 10Ω?

23. 3.02 - Electric Current Calculating Power
What is the resistance of a circuit with 20V and 2A?

24. 3.02 - Electric Current Calculating Power
What is the resistance of a circuit with 20V and 2A?

25. 3.02 - Electric Current Calculating Power
What is the current in a 20V circuit if the resistance is 10Ω?

26. 3.02 - Electric Current • Alternating Current
– Electrons flow initially in one direction then in the opposite direct
– Generators create alternating current by electromagnetic induction
– Power company uses a transformer to step up the voltage to transfer to your home; then a transformer near your house steps the voltage down.

27. 3.02 - Electric Current • Direct current
– Electrons that flow in one direction
– Batteries produce direct current
– Current moves from negative to positive

28. Electric Current

29. Electric Current
Wet Cell
Dry Cell

30. 3.03 - Circuits • Circuits • Every complete circuit contains
– a voltage source (such as a battery)
– an unbroken path along which electrons can move.
– contain some type of device that uses the electric current to do work.

31. 3.03 - Circuits • Open Circuits
• Switches work to open and close a circuit

32. 3.03 - Circuits • Circuit Diagrams
• Symbols represent circuit components
lamp
motor
battery
resistor
switch
voltmeter
buzzer
ampmeter

33. Circuits
Every component in a circuit slows the flow of electrons through the circuit to some degree.
• You can think of resistance as being similar to friction. Just as friction slows the motion of an object by converting kinetic energy into heat, resistance slows the flow of electrons by converting their kinetic energy into heat.
• Because resistance in a circuit slows the flow of electrons, it affects the amount of current (amperage) in the circuit.
• As resistance increases, current decreases if voltage remains the same.
• If voltage increases but resistance stays the same, current increases..

34. 3.03 - Circuits • Importance of Ohm’s Law
• certain electrical components are used specifically to create resistance.
• Resistors are not very good conductors, so they slow the electron movement down.
• Resistors are commonly used to decrease the current in a circuit.

35. 3.03 - Circuits • Series Circuits – One path for electrons
– One bulb out, they all go out
– More components, less current

36. 3.03 - Circuits • Parallel Circuits – More than one path for electrons
– One bulb goes out, rest stay lit
– No change in current

37. 3.03 - Circuits • Parallel/Series Circuits
– Complex circuits combine series and parallel

38. 3.03 - Circuits • Household Circuits – Safety Devices • Fuses
• Circuit breakers

39. Electromagnetism
• The mineral magnetite - has the strongest magnetic properties of any naturally occurring minerals.
• Samples of this mineral have north and south poles.
• North and south poles of two different samples attract one another, and like poles (north–north or south–south) repel one another.

40. 3.04 - Electromagnetism • Magnetism – • Magnetic forces –
– Magnetic poles produce magnetic forces
– Forces based on
• Strength of magnets
• Distance between magnets
• Like poles repel; opposite poles attract

41. Electromagnetism

42. 3.04 - Electromagnetism Magnetic Field Direction
• Always points away from north pole toward south pole

43. 3.04 - Electromagnetism • Magnetic field – – Direction of field
– Lines closer together versus farther apart

44. 3.04 - Electromagnetism • Magnetic Materials – Magnetic domains –
– What makes a magnet?
– Permanent magnets vs. temporary magnets

45. Electromagnetism
Magnetic poles cannot exist by themselves; north pole must have a south pole

46. 3.04 - Electromagnetism • Earth’s Magnetic Field
• A compass responds to this magnetic field
• The magnetic poles of the Earth are opposite to its geographic poles; the geographic north pole is actually the magnetic south pole and the geographic south pole is the magnetic north pole.

47. Electromagnetism
• Magnetic fields can be made by a single moving charge or a current of charges
• Electromagnets –
• Superconducting Electromagnets -

48. Electromagnetism
• Electric current can be produced from magnetism
• Motion of magnet in coil of wire
• Electromagnetic Induction -
• Induced voltage affected by
– Number of loops of wire
– Magnitude of motion (fast vs. slow)

49. Electromagnetism
• A electrical field can be induced by a magnetic field spinning inside a coil of wire..
• A magnetic field is induced in an region of space in which an electric field is changing with time.
• Magnetic Force on Current-Carrying Wire

50. Electromagnetism
– An electrical field is induced in any region of space in which a magnetic field is changing with time
– A magnetic field is induced in an region of space in which an electric field is changing with time.
• Break it Down – Magnetic fields can create electrical fields and Electrical fields can create magnetic fields.

51. 3.04 - Electromagnetism • Uses for Electromagnets • Scrap Yards
• Computers
• MRIs

52. 3.04 - Electromagnetism • Electric Meters – Galvanometer
– May be calibrated to measure current or voltage
• Electric Motors
– Motor current changes direction each time coil makes a half rotation

53. 3.04 - Electromagnetism • A generator is a motor in reverse
• Motor = electrical energy in, mechanical energy out
• Generator = mechanical energy in, electrical energy out
• Generators don’t produce energy – they convert energy from some other form to electrical energy

54. 3.05 Energy Resources • Non-renewable Resources
• Resources used at a faster rate than they can be replaced
• Fossil Fuels
– Oil (Petroleum)
– Natural Gas
– Coal

55. 3.05 Energy Resources
• Power plant powered by Fossil Fuels

56. 3.05 Energy Resources • Coal – Used to produce half the electricity
– Solid form of carbon
– Diminishing supply
– Gives off carbon dioxide when burned
– Produces emissions that pollute air and water

57. 3.05 Energy Resources • Petroleum – Refined from crude oil
– Used as fuel in electrical power plants
– Used as automobile fuel, heating fuel, fertilizer, industrial uses
– Burning produces carbon dioxide

58. 3.05 Energy Resources • Natural Gas
– Burned 2nd most common energy source in electrical power plants
– Used for heating and cooking
– Burning produces carbon dioxide
– Also produces emissions that pollute air and water

59. 3.05 Energy Resources • Nuclear Power
– Also used in nuclear power plants to create electricity
– Uses fission of uranium
– Cleaner compared to fossil fuels
– Radiation, radioactive wastes, and safety are concern to environment

60. 3.05 Energy Resources
• Three Mile Island
• Chernobyl
• Fukishima

61. 3.05 Energy Resources • Renewable resources
• Can be replaced at the same rate or even faster than they are used
– Solar
– Wind
– Hydropower
– Geothermal
– Biomass
• Provide less than 10% of world energy, but growing
• Do not contribute directly green house gases

62. 3.05 Energy Resources • Solar Power
– Converts energy from Sun to electricity
– Can be passive heating
– Can use photovoltaic cells

63. 3.05 Energy Resources • Wind Power
– Converts kinetic energy of wind into electricity
– Lots of space needed for turbines
– Only certain areas of the world supply enough wind

64. 3.05 Energy Resources • Hydropower
– Kinetic energy from flowing water is converted into electricity
– Provides most energy of any renewable resource
– Displace wildlife, people, alter natural flow of rivers, affect fish migration

65. 3.05 Energy Resources • Geothermal
– Comes from heat buried in the Earth
– Used to heat water for steam to produce electricity
– Expensive to build
– Cn only be built in certain locations
– Emission and pollution free

66. 3.05 Energy Resources • Biomass
– Includes wood, garbage, and agricultural waste
– Makes use of garbage and other waste instead of fossil fuels
– Still produces pollutants and carbon dioxide

67. 3.05 Energy Resources • Why not Use More Renewable Resources?
– Cost – generally more expensive
– Location – often located in remote areas, expensive to build power lines
– Limitations – Not always available or practical
• More advances must be made in the area of renewable resources if we are going to limit our dependence on fossil fuels.

68. 3.06 – Human Impacts on the Environment
• In order to meet needs for food, lodging, energy, and transportation, humans impact the world around us in negative ways
– Oil spills
– Groundwater
– Waste disposal
– Ozone Depletion
– Air Pollution
– Water Pollution

69. 3.06 – Human Impacts on the Environment
• Oil Spills
– Release of crude oil, petroleum, gasoline, or diesel fuel into the environment
– Affect birds, animals, and marine life
– Limit photosynthesis of marine plants and affect entire food chains
– Increased regulations, improved shipping containers, and taking action to clean up after a spill occurs

70. 3.06 – Human Impacts on the Environment
• Groundwater
– Water located beneath the ground surface
– Pollutants can contaminate
• Pesticides an fertilizers, animal and livestock waste, leaking septic tanks and sewers, motor oil and household chemicals
– Movement of water can spread contaminates

71. 3.06 – Human Impacts on the Environment
• Waste Disposal
– Garbage waste burned or buried (landfill)
– Still risk of contamination of water or soil
– Methane gas (landfills) and carbon dioxide (burning) contaminate air

72. 3.06 – Human Impacts on the Environment
• Ozone Depletion
– Ozone naturally occurs in Earth’s upper atmosphere and at ground level
– Chloroflourocarbons, methyl bromide, carbon tetrachloride, and methyl chloroform break down ozone
– Ozone depleting chemicals used in coolants, foaming agents, fir extinguishers, solvents, pesticides, and aerosol cans

73. 3.06 – Human Impacts on the Environment
• Air Pollution
– Ozone
– Particulate Matter
– Carbon monoxide
– Nitrogen Oxides
– Sulfer Dioxide
– Lead
• These chemicals or small particles into the air can be damaging to the environment and people’s health

74. 3.06 – Human Impacts on the Environment
• Water Pollution
– Pollution of any surface water (lakes, rivers, and oceans)
– Sources of water pollution include nitrates, phosphates, silt and suspended solids, bacteria, viruses and protozoan, petroleum and oil spills, radioactive substances, heat

75. 3.06 – Human Impacts on the Environment
• Positive Impact of Technology
• Some advances in technology have lessen the negative impacts of humans on the environment
– Recycling
– Energy Efficiency
– Environmental Remediation
– Water Treatment

76. 3.06 – Human Impacts on the Environment
• Recycling
– Using materials again
– Paper, aluminum, glass, and rubber
– Reusing items is another form of recycling
– Reduces energy use and saves natural resources

77. 3.06 – Human Impacts on the Environment
• Energy Efficiency
– Performing functions using less energy
– CFL light bulbs, fuel efficient cars, energy efficient appliance
– Construction technologies – low flow plumbing, improved insulation

78. 3.06 – Human Impacts on the Environment
• Environmental Remediation
– Removal of pollutants or contaminants
– Improvements in technology and in storage of fuel and waste have reduced pollution
– Close monitoring of pollution emitted from power plants, transportation, and industry

79. 3.06 – Human Impacts on the Environment
• Water Treatment
– Providing clean, pollution free water people around the world
– Reduce pollutants and contaminants
– Advances in technology have cut down on pollution
– Reducing amount of fossil fuels burned can decrease air and water pollution

80. 3.06 – Human Impacts on the Environment
• What Can You Do?
– Save gas
– Recycle
– Conserve water
– Use reusable grocery bags
– Conserve electricity