my_electric_bill_answers

my_electric_bill_answers - does the refrigerator use each...

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My Electric Bill or What are my cold drinks costing me? Attached is a copy of my recent electric bill. Con Ed says that I used 142 kilowatt-hours over 31 days. They’re charging me $.183 per kilowatt-hour. ”KWH” means ”kilowatt-hours”. One kilowatt equals 1000 watts. So a kilowatt is a unit of power . One kilowatt-hour equals the energy to run an appliance using 1000 watts for 1 hour. So a kilowatt-hour is a unit of energy . Con Ed says I used 142 KWH over 31 days, so I use an average of 142 KWH/ 31 days = 4.58 KWH/day. Suppose I run a 100 watt light bulb for 4 hours each day for my total lighting needs. How many KWH do I use for lighting each day? .1 kW * 4 hours/day = .4 KWH/day The rest of my energy usage goes to the refrigerator. How many KWH
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Unformatted text preview: does the refrigerator use each day? ( 4.58 KWH/day - .4 KWH/day = 4.18 KWH/day ) Since ConEd charges me $.183 per KWH, how much does it cost me to run the refrigerator each day? $ .183/KWH * 4.18 KWH/day = $ .765/day (76 and a half cents a day). What power is used by the refrigerator in watts ? The fridge is always on (24 hours a day) so Power = energy used/time = 4.18KWH/24 hr = .174 kW = 174 watts. What current is used by the refrigerator? Use P = VI, we know P=174 watts, V=120 volts (household)so: I = P/V = 174W/120V = 1.45 A (amps). What is the resistance of the refrigerator? Use Ohms Law: V=IR or R=V/I and we know V and I, so R=V/I=120V/1.45A = 82.7 (ohms). 1...
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This note was uploaded on 10/19/2011 for the course PHY 2020 taught by Professor Staff during the Spring '08 term at University of Florida.

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