fou are part of an engineering firm on contract by the US De

fou are part of an engineering firm on contract by the U.S. Department of Energy\'s Energy EMciency and Renewable Energy task force to develop a program to help consumers measure the fficiency of their home appliances. Your job is to measure the efficiency of stove-top burners. The consumer wil place a pan of room temperature water on their stove (with 1 gallon of water), record the initial room temperature in units of degrees Fahrenheit, turn on the burner, and wait for it to boil. When the water begins to boil, they will record the time in units of minutes it takes for the water to boil Finaly, they will look up the power for the burner provided by the manufacturer. Using all of this information provided by the user, determine the efficiency of their burner. Assume the specific heat of water is 4.18 joules per gram degree Celsius. (Round your answers to three significant digts. Click the ioon to view conversion formulas for temperature scales. Click the icon to view the conversion table. | Stove Model (a) Krispy 32-Z | Room Temp rF) | Time to Boil [min] | Rated Burner Power My 1,200 | Efficiency(%) 74 19

Solution

volume = 1 gallon = 3.78541 litre

density of water = 1000 g/litre

c = 4.18 Joule/gram ^oC

room temperature = 74 F = 23.3333 C

final temp =100 C

change in temp = 76.66666 C

time = 19 min = 19*60

so power =   3.78541*1000*4.18*76.6666/(19*60)

= 1064.1207 W

hence efficiency = 1064.1207/1200 = 0.886767 = 0.887

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