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AST406 Energy & Cost

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AST406 Energy & Cost

1. 1. Energy and Cost Objectives: 4.1 Determine the cost of using an electrical appliance 4.4 Identify the units that define electric energy, using the variables associated with electric circuits
2. 2. Energy  Energy:  the Wh en at is er g y? ability to do work  all appliances need energy to work  ex. a remote control needs energy from batteries to work  ex. a light bulb needs electrical energy to shine bright
3. 3. Power  Wh po at is we r? Power:  the rate at which energy is produced  is the product of potential difference (voltage) & current intensity
4. 4. Symbols and Units Symbol = Symbol = Units Units = =
5. 5. E = P•t Time Energy Joules (J) Seconds (s) Power Watts (W)
6. 6. A stereo has a power rating of 200W & is used for 1800 seconds. How much energy is used? E = P•t E = (200)•(1800) E = 360,000 J 360,000 Joules of energy were used to work the stereo
7. 7. A video game has a power rating of 175W & is used for 3600 seconds. How much energy is used? E = P•t E = (175)•(3600) E = 630,000 J 630,000 Joules of energy were used to work the video game
8. 8. A hair dryer has a power rating of 425W & is used for 10 minutes. How much energy is used? E = P•t E = (425)•(600) Time must be in seconds 10 min x 60 = 600 seconds E = 255,000 J 255,000 Joules of energy were used to work the hair dryer
9. 9. P = V •I Power Watts (W) Current Amps (A) Potential Difference Volts (V)
10. 10. A toaster requires 120V & 6A to work. What is its power? P = V•I P = (120)•(6) P = 720 W The toaster has 720 watts of power
11. 11. An appliance requires 240V & 2A to work. What is its power? P = V•I P = (240)•(2) P = 480 W The appliance has a power of 480 watts
12. 12. Tric ky Que s tio n An appliance requires 120V & 12A to work. It is used for 900 seconds. How much energy is used? P = V•I E = P•t P = (120)•(12) E =(1440)•(900) P = 1440 W E =1,296,000 J
13. 13. Tric ky Que s tio n An appliance uses 225V & 4A to work. It is used for 60 minutes. How much energy is used? 60min x 60 P = V•I E = P•t P = (225)•(4) E =(900)•(3600) P = 900 W E =3,240,000 J
14. 14. Activties  P. 173, Q. 17-20
15. 15. E = P•t Energy (kWh) Time Power Hours Watts (kW) (hr)
16. 16. KWh Question  How much energy is used if a 1500 W speaker is used for 3 hours?  E = Pt = 1.5 kW * 3 hr = 4.5 kWh  
17. 17. Cost Every time you use an appliance it costs money……how do you calculate how much it will cost? C=RaPt! (Usually Given) Must be in kW Remember: 1000 watts = 1 kW Must be in hours
18. 18. A 4800 watt television is used for 5 hours. If the cost of electricity is \$0.04kW•h, what would your bill read? (How much would it cost?) Cost = rate of electricity x Power x Time cost = \$0.04 × 4.8kW× 5h cost = \$ 0.96 4800 w = 4.8 kW
19. 19. A 1500 watt hair dryer is used for 30 minutes. Electricity costs \$0.05/kW•h. How much does it cost to use this hair dryer for the period indicated? Cost = rate of electricity x Power x Time cost = 0.05 × 1.5kW × 0.5 h 1500 w = 1.5 kW 30 min ÷ 60 min = 0.5 hrs cost=\$ 0.0375
20. 20. A 3.9 kilowatts curling iron is used for 10 minutes once a day. Electricity costs \$0.05/kW•h. How much does it cost to use this curling iron for a week? Cost = rate of electricity x Power x Time cost = 0.05 × 3.9 kW × 0.167 h 10 min ÷ 60 min = 0.167 hrs cost=\$ 0.0325 X 7 days cost=\$ 0.23
21. 21. Cost & Rating Plates  Every electrical appliance has a rating plate. Model: VCANN-1977 Serial No: Look for power 240 V 60 Hz POWER 2005-13 4000 W Rating plates allow us to calculate the electrical cost of an appliance.
22. 22. The rating plate for an electric hair dryer is given below. Model: LHOPE-1979 1500 W 200V 40Hz If the dryer is used for 30 minutes a day & the cost of electricity is \$0.04/kW•h, how much would it cost to use every day? Cost = cost of electricity x power x time Cost =(\$0.04/kW•h) x (1.5kW) x (0.5h) Cost =\$0.03 or 3 ¢
23. 23. The rating plate for a television is given below. Model: CANNHOPE-2005 2500 W 250V 60Hz If the TV is used for 2 hours a day & the cost of electricity is \$0.05/kW•h, how much would it cost to use for a 30-day month? Cost = cost of electricity x power x time Cost =(\$0.05/kW•h) x (2.5kW) x (2h) Cost =\$0.25 x 30 days Cost =\$7.50
24. 24. No power!! Recall P = VI P = (200)(6) P = 1200 W The rating plate for an electric appliance is given below. Model: NOV-05 30Hz 200V 6A If the appliance is used for 1 hour a day & the cost of electricity is \$0.0475/kW•h, how much would it cost to use every day? ? Cost = cost of electricity x power x time Cost =(\$0.0475/kW•h) x (1.2kW) x (1h) Cost =\$0.057 or \$0.06
25. 25. No power!! Recall P = VI P = (375)(0.2) P = 75 W The rating plate for an electric appliance is given below. Model: RAF-2005 375V 0.2A If the appliance is used for 3 hours a day & the cost of electricity is \$0.05/kW•h, how much would it cost to use for a week? ? Cost = cost of electricity x power x time Cost =(\$0.05/kW•h) x (0.075kW) x (3h) Cost =\$0.01125 x 7 days Cost =\$0.08
26. 26. The rating plates of four different electric appliances are used below A) 860 W 120V 60 HZ GIN-4445 B) 1400 W Each appliance is used for 4 hours. Which of these appliances would be the most expensive to use? 15 A 140 V MAC-2453 C) 10 A 125 V MANDANE-2445 D) 2A 250 V 66 HZ I8JUL-6712 P=VxI Since the cost and time are the same you must just look for power… P = 10 x 125 P = 1250 W P=VxI P = 2 x 250 P = 500 W By comparing Power it is clear to see that appliance “C” would be the most expensive!
27. 27. Recalling Units  Joule : a unit of energy   W Ex.: 100 W light bulb Volt : energy per unit charge  A Ex.: 15 ampere breaker Watt : a unit of power   Ex.: 25 g of candy contains 276 000 J ampere : a quantity of charges per time   J Ex.: AA battery has 1.5 volts V
28. 28. Important Units to Remember It is important to remember the following units for power and time. Joules Watts W•s kW kw•h V•A•s
29. 29. Electricity uses the following units: 1. Watt 4. Kilowatt-hour 2. Volt 5. Joule 3. Ampere Which of the above are units of energy? 1 and 3 B) 2 and 4 C) 1 and 5 D) 4 and 5 A) Energy Power Joules Watts W•s kW kw•h V•A•s
30. 30. Which of the following units are not units of energy? 1. W 2. V•A•s 3. J 4. A 5. kW•h 6. W•s Energy Power 1, 3, and 4 B) 1 and 4 C) 1, 4, and 6 D) 4 and 5 A) Joules Watts W•s kW kw•h V•A•s
31. 31. KEY POINTS - FORMULAS E=Pxt P=VxI Cost = cost of electricity x P x t **make sure you have the correct units in these formulas** - UNITS Energy Power Joules Watts W•s kW kw•h V•A•s
32. 32. Activities   Student Study Guide, Module II-16 & II-17 WORKSHEET # 16