Do Now #33…

1. Do Now #33… • Explain the right hand rule and what is meant by it.

2. Objective… • I will be able to describe how electricity is made in a magnetic field.

3. Today we will explore electrical energy, better known as electricity So What Exactly Is Electricity? Electricity by definition is electric current that is used as a power source! This electric current is generated in a power plant, and then sent out over a power grid to your homes, and ultimately to your power outlets.

4. I guess the next question would be... What is Electric Current? The movement of charges such as electrons is called current, and this electrical current is what powers household appliances. Charge Passing Through A Given Area ------------------------------- Time Electric Current =

5. An easier way to think of electric current is to picture cars going through a Turnpike or Parkway Toll. The cars could represent electrons or charge, and the toll booth could represent the cross sectional area of the wire at a certain point. If you counted the number of cars or electrons, that passed through the toll booth or a certain cross sectional area of the wire, and divided that number by the time it took for those cars or charges to pass, you would get the current!

6. So How Is An Electric Current Generated? Electric current generation - whether from fossil fuels, nuclear, renewable fuels, or other sources is usually based on the: Simple Equation For Electricity Generation

7. What does copper wire and magnets have to do with Electricity? In September of 1831, Michael Faraday made the discovery of Electromagnetic Induction. Faraday attached two wires to a disc and rotated the disc between the opposing poles of a horseshoe magnet creating an electric current.

8. Motion is Essential If you place a magnet and a conductor (copper wire), in a room together there will be no electric current generated. This is because motion, from our equation for electricity, is missing! An electric current is not generated unless the magnetic field is moving relative to the copper wire, or the copper wire is moving relative to the magnetic field.

9. Simple Electric Generator So simple electric generators found in power plants contain, magnets and copper wire that when put into motion relative to one another create the electric current that is sent out to homes. The major problem in electricity generation Is where does the Motion come from that keeps the copper wire and magnets moving relative to one another. In this case, wind power applies a force to the blades that turns them. The spinning blades, spin an armature that turns the copper wire relative to the magnetic field. As long as the blades spin, electricity will be generated!

10. Electricity Transmission • - AC of 60 Hz produced by generator • Resistance losses are smallest at high voltages and low currents

11. What Happens At Home? At home, electric current that was generated by generators in the power plant is used to power electric appliances. The electric current, running through the copper wire causes the armature to spin which is how most motors generate motion.

12. Now back to the major question! Where does the motion needed to keep the copper wire moving relative to the magnetic field come from? • attains between 50 – 70% efficiency • - one windmill’s average energy • output ranges from 11.4 W/m^2 – • 57 W/m^2 depending on how windy • wind farms tend to generate between • 50 and 600 Kw - California currently produces ¾ of all the wind generated electricity in the world. Wind generated Kilronan Wind Farm In Ireland -North Dakota with 20 times the wind potential of California has not erected a single wind turbine

13. Annual Average Wind Power Density @ 50m Wind power classes 3 (300-400 W/m2) to 7 (800-2000 W/m2) are suitable for wind power development

14. Problems With Wind Power • Wind variability must be overcome by system design - Basic energy Storage Enviornmental Concerns - Differences in pressure gradients around wind turbines affect birds • Noise from the turbines affects people and animals • Eyesore, the appearance of mile after mile of wind machines with • transmission lines is of concern to the public

15. Hydroelectric Power • Conversion from potential energy of • water to electric energy is at 80 – 90% • efficiency -Hydroelectric projects in the United States have rated capacities from 950 – 6480 MW • The use of Water Power is much • greater in some other countries. • Norway obtains 99% of its electricity • from water power. Nepal, Brazil, and • New Zealand are close seconds. Water generated - Hydroelectric Shasta Dam In California

16. The Hydrologic Cycle

17. - Hydroelectricity has dropped from producing 30 % to 10% of US electricity - Large fluctuations in output are mainly due to variable rainfall totals

18. Problems With Hydroelectric Power • About 50% of the United States potential for hydroelectric energy has been • tapped. However, further advances are unlikely. • The Wild and Scenic River Act and the Endangered Species Act have • inhibited development of some sites • Silt collection in hydroelectric Dam storage volumes over time causes • maintenance issues, as well as environmental concerns • The loss of free flowing streams and land due to flooding behind the dam • disturbs the life of species: eg – Salmon - Possibility of dam failure

19. Fossil Fuels – Oil Refinery Pasadena - Texas Standard Large Power Plants Provide 1 Giga-watt of electric power and releases 2 Giga-watts of thermal power as waste heat. An efficiency averaging around 30%. • 9000 tons of coal a day • 40,000 barrels a day or one tanker a week of oil • -generates about 5.3 x 10^9 kwh/year • -powers a city of a million people

20. Where do Fossil Fuels come from?

21. total world production in 1996 of • petroleum is 62,239e3 barrels / day • an average well in the US produces • only 11 barrels / day • In Saudi Arabia an average well • produces 9600 barrels /day Oil Drilling Platform Cook Inlet, Alaska

22. How do fossil fuels create motion?

23. Fuel Efficiency Over Time

24. -There are 109 power reactors in the United States -Produce 22% of nation’s electricity - In France 79% of electricity comes from nuclear reactors Nuclear Power • Plant electrical output 1220 MW • -Plant efficiency 34% Diablo Canyon - California

25. The Reactor Big Picture

26. Nuclear Energy Problems and Concerns • In normal operations a nuclear reactor produces some environmental • emissions. E.g.: escape of radioactive fission products through cracks and • diffusion, radioactive H3 in small amounts in discharged water • Core meltdown are possible, but unlikely due to negative feedback and • shutdown systems • Even after shutdown there is 7% of normal power generation still in the • reactor fuel rods. This may be sufficient enough to melt core and destroy • the reactor, if cooling water is not supplied • A study entitled “Severe Accident Risks: An Assessment for Five US • Nuclear Power Plants” conducted by NRC in 1990, shows that for all the • 109 reactors now operating in the United States over a 30 year lifetime • there is about a 1% chance of a large release due to internal events.

27. Other Energy Considerations • Solar Power – uses the sun energy to either boil water or directly converts • solar energy to electrical energy • Ocean Thermal Energy Conversion – uses temperature differences • between different depths of ocean water to drive a heat engine. Working • fluid is ammonia which is gas at room temperature. -Biomass Energy: Municipal Solid Waste – burning wastes to drive heat engines • Geothermal Energy – based on naturally occurring heat in the Earth in the • Earth due to radioactive decay • Tidal Energy – uses the gravitational pull of the moon on our oceans to • drive turbines

28. Proportion of World’s energy consumption - 1997 Proportion of the world’s Electricity generation - 1997

29. Trend of the growth of energy sources

31. Do Now #34… • Explain what the formulat V=IR stands for. If you don’t know be creative.

32. Objective… • I will be able to decribe the equation V=IR and explain what each component means and what happens when each variable it changed. • I will also build a simple electrial magnet based upon the right hand rule and V=IR equation.

33. Do Now #35… • How much resistance in ohms does a battery have that produces 12 Volts at 120 amperes (amps)?

34. Objective…. • I will be able to calculate the different

35. What is electricity? The collection or flow of electrons in the form of an electric charge

36. What is static electricity? When two objects rub against each other electrons transfer and build up on an object causing it to have a different charge from its surroundings. Like the shoes rubbing against the carpet. Electrons are transferred from the carpet to the shoes.

37. As electrons collect on an object, it becomes negatively charged. As electrons leave an object it attains a positive charges. Charges interact with each other: Often when you remove clothes from the clothes dryer, they seem to stick together. This is because some of the clothes have gained electrons by rubbing against other clothes. The clothes losing electrons become positive. The negative clothes are attracted to the positive clothes. Have you ever rubbed a balloon on your hair and stuck it on a wall? How do you think this works?

39. The van de Graaf generator (large silver ball) deposits electrons on the ball. When a person places their hand on the ball and the machine is turned on, electrons are transferred to and collected on the person touching the silver ball. Why do you think this machine affects the hair of the children in the picture?

40. What causes you to be shocked when you rub your feet across carpet? An electrical discharge is the passing of an electric current through the air from a negatively charged object to a positively charge object. This is what causeslightning!

41. Check out these static electricity video clips • Static electricity at a gas station • Van de Graaf Generator’s effect on human hair • Static on Baby’s hair • Kid gets static going down a slide • “Cat abuse” by static electricity What is a conductor and insulator? A conductor is a material which allows an electric current to pass. Metals are good conductors of electricity. An insulator is a material which does not allow an electric current to pass. Nonmetals are good conductors of electricity. Plastic, glass, wood, and rubber are good insulators

42. How are static charges detected?

43. What is the difference between staticelectricity and currentelectricity? Static electricity is stationary or collects on the surface of an object, whereas current electricity is flowing very rapidly through a conductor. The flow of electricity in current electricity has electrical pressure or voltage. Electric charges flow from an area of high voltage to an area of low voltage. Water pressure and voltage behave in similar ways.

45. The pressure of the water flowing through the pipes on the last slide compare to the voltage (electric potential) flowing through the wires of the circuit. The unit used to measure voltage is volts (V). The flow of charges in a circuit is called current. Current (I) is measured in Amperes (A).

46. What are batteries? Batteries are composed of a chemical substance which can generate voltage which can be used in a circuit. There are two kinds of batteries: dry cell and wet cell batteries. Below is an example of a dry cell. The zinc container of the dry cell contains a moist chemical paste surrounding a carbon rod suspended in the middle.

47. Wet cell batteries are most commonly associated with automobile batteries. A wet cell contains two connected plates made of different metals or metal compounds in a conducting solution. Most car batteries have a series of six cells, each containing lead and lead oxide in a sulfuric acid solution.

48. What is electrical resistance? Resistance (R)is the opposition to the flow of an electric current, causing the electrical energy to be converted to thermal energy or light. The metal which makes up a light bulb filament or stovetop eye has a high electrical resistance. This causes light and heat to be given off.

49. The unit for measuring resistance is the ohm (Ω).

50. Electrical Calculations – What is Ohm’s Law? 3 V I = 1.5 amps I = 2 Ω