1. Understanding Electricity

2. Electric Current Electric current: the flow of electrons through a conductor (like silver, copper, gold, or aluminum) Electrons move in no particular direction, therefore there is no electric current Electrons move in one direction, therefore there is an electric current

3. Magnets & Electricity An electric current is produced when a magnet is moved into a coil of wire in a circuit

4. Magnets & Electricity http://www.youtube.com/watch?feature=pl ayer_embedded&v=P3kJd3MDeukhttp://www.youtube.com/watch?feature=pl ayer_embedded&v=P3kJd3MDeuk

5. Vine Day Saturday, February 20 9 am – 12 pm George Lorimer Preserve North Valley Road Parking Lot

6. Open Circuit

7. Closed Circuit

8. Voltage Voltage is the measure of the force that “pushes” electrons through a circuit Similar to the pressure of water pushing it through pipes

9. Electric Current Current is a flow rate of electrons in a circuit and is measured in amperes 1 ampere (amp) = 6.24 x 10 18 electrons per second Similar to the flow of water through pipes

10. Power Power = energy ÷ time Ex: –There is more energy in 1 kg of coal than 1 kg of TNT –But, TNT delivers more power because it releases its energy in much less time

11. Electric Power Power is the rate that energy is generated or consumed A watt is 1 Joule per second –Ex: lifting a small apple 1 meter in 1 second 1 watt is equal to the rate of current flow when 1 volt moves 1 amp through a circuit

12. Putting It All Together Watts = Volts x Amps Ex: Calculate the wattage of a set of speakers with 120 V and 2.5 amps W = 120V x 2.5A = 300 W Ex: Calculate the amps if the voltage is 120 and the appliance is rated at 650W A = 650W ÷ 120V = 5.4 amps

13. Scale of Electricity Kilowatt = 1,000 watts –Enough to power an average American home at any one time Megawatt = 1 million watts –Enough to light a stadium at night Gigawatt = 1 billion wattsGigawatt –Enough to power a major city

14. Power Plants Limerick’s two reactors produce 2,345 megawatts of electricity in total Enough to power more than 2 million average American homes

15. Electrical Consumption Power is the rate that energy is generated or consumed, not the amount of energy The rate of energy that a light bulb uses at any moment would be measured in watts The amount of energy a light bulb uses over an entire day would be measured in watt-hours (Wh)

16. Electrical Consumption Electricity is typically sold by the kilowatt hour (kWh) 1 kWh = 1,000 W of power used for 1 hour 1 MWh = 1,000,000 W of power used for 1 hour

17. Relationship Between Energy & Power Energy = power x time kWh = kW x h kWh = energy kW = power h = time

18. Relationship Between Energy & Power A 10 kW wind turbine can generate 10 kW of power under optimal conditions It would be foolish to ask, “How long does it take to generate 10 kW?” –It’s similar to asking, “How long does it take to travel 10 miles per hour?” –10 kW is the rate that it can generate energy, not the amount of energy it can generate in a period of time

19. Relationship Between Energy & Power Energy is like distance – it’s an amount Power is like speed – it’s a rate

20. Typical Wattages of Various Appliances Clock radio = 10W Clothes washer = 350–500W Clothes dryer = 1800–5000W Dishwasher = 1200–2400W Hair dryer = 1200–1875W Clothes iron = 1000–1800W Microwave = 750–1100W Refrigerator = 725W Toaster = 800–1400W DVD = 20–25W Vacuum cleaner = 1000–1440W Water heater = 4500–5500W Laptop = 50W

21. Electricity Bill

23. Energy Calculation Problems

24. Energy Calculation Problems A major coal fired electrical power plant produces 44,200,000,000 BTU of electrical energy per day. Assuming that one pound of coal can produce 5,000 BTU, how many pounds of coal are used by the plant each day? 44,200,000,000 BTU x (1lb. coal/5,000 BTU) = 8,840,000 lbs. coal

25. Energy Calculation Problems In 2008, the average American home used about 11,000 kWh of electricity. Suppose the electricity in your region was supplied by the burning of natural gas. How many cubic feet of natural gas is needed to support your energy lifestyle? 1 kWh = 3,410 BTU 1 ft 3 natural gas = 1,030 BTU 1 BTU = 1,055 J 11,000 kWh x (3,410 BTU/1 kWh) = 37,510,000 BTU 37,510,000 BTU x (1 ft 3 /1,030 BTU) = 36,417 ft 3 natural gas

26. Energy Calculation Problems In 2008, the average American home used about 11,000 kWh of electricity. Suppose the electricity in your region was supplied by the burning of coal. How many pounds of coal are needed to be burned? 1 kWh = 3,410 BTU 1 lb. of coal = 12,000 BTU 1 BTU = 1,055 J 11,000 kWh x (3,400 BTU/1 kWh) = 37,510,000 BTU 37,510,000 BTU x (1 lb./12,000 BTU) = 3,125 lbs. of coal

27. Energy Calculation Problems A dishwasher has a power rating of 2,000 W. It’s used for 3 hours each week. If electricity costs $0.10 per kWh, how much will it cost for a year’s worth of dishwashing? 2,000 W x 1 kW/1,000W = 2 kW 2 kW x 3 h/week = 6 kWh/week 6 kWh/week x 52 weeks = 312 kWh 312 kWh x $0.10/kWh = $31.20

28. Energy Calculation Problems A power plant uses 4,500 tons of coal each day. Each pound of coal can produce 5,000 BTU of electrical energy and 3,400 BTU are equivalent to 1.0 kWh of energy. How many kWh of energy are produced by the plant each day? 4,500 tons/day × 2,000 lbs./ton × 5,000 BTU/lb. × 1.0 kWh/3,400 BTU = 13,235,294 kWh

29. Energy Calculation Problems 1.How much energy (in Joules) does a 75 Watt light bulb use when it is turned on for 25 minutes? 75 W × (1 J/s / 1 W) × (60 sec/1 min) × (25 min) = 112,500 J

30. Energy Calculation Problems 2. A 100 Watt light bulb is 20% efficient. a) How many Joules does it use in 12 hours of operation? 100 W × (1 J/s / 1 W) × (60 sec/1 min) × (60 min/ 1 hr) × 12 hr = 4,320,000 J

31. Energy Calculation Problems b) How much energy (in Joules) does the bulb convert to light during 12 hours? 4,320,000 J × 0.2 = 864,000 J light

32. Energy Calculation Problems c) How many kWh does it use in 12 hours of operation? 100 W × (1 kW/1,000 W) × 12 hr = 1.2 kWh

33. Energy Calculation Problems 3. An electric clothes dryer has a power rating of 4000 W. Assume a family does 5 loads of laundry each week for 4 weeks. Each dryer load takes 1 hour to complete. a)Find the energy used in Joules and kWh. 4000W × (1 J/s / 1 W) × (3600 s/hr) × (1 hr/load) × (5 loads/week) × (4 weeks) = 288,000,000 J 288,000,000W× (1 Wh/3,600s) = 80,000 Wh = 80 kWh