You are part of an engineering firm on contract by the U.S. Department of Energy

Question

You are part of an engineering firm on contract by the U.S. Department of Energy's Energy Efficiency and Renewable Energy task force to measure the power efficiency of home appliances. Your job is to measure the efficiency of stove-top burners. In order to report the efficiency, you will place a pan containing one gallon of room temperature water on their stove, record the initial room temperature, turn on die burner, and wait for it to boil. When the water begins to boil, you will record the time it takes the water to boil and look up the power for the burner provided by the manufacturer. After measuring the following stove-top burners, what is the efficiency of each burner? The specific heat capacity of water is 4.18 J/(g C). Click the icon to view conversion formulas for temperature scales. Click the icon to view the conversion table. Complete the table below. (Round your answers to three significant digits.)

Explanation / Answer

heat transferred to water= maass of water*specific heat* (boiling point of water-room temperature)

given volume of water= 1gallon= 3.785 liters=3875 cc

assumed water density over the given temperature = 1g/cc

mass = volume * desnity =3875*1= 3875 gms

Cp of water =4.18 jure /g.deg.c

Boiling temperaute (assumnig a pressure of 1 am) =100 deg.c

Room temperature = 61 deg.F

This needs to be converted to deg.c by

F= 9/5C +32

61=1.8C+32

C= (61-32)/1.8= 16.11 deg.c

heat transferrred = 3875 (g) * 4.18 (j/g,c)*( 100-16.11)deg.c = 1358808 Joules

the tme take = 21 min =21*60 seconds = 1260 seconds

heat transferred / unit time ( output) =1358808/1260 j/s=1078.419Watts

Rated power= 1800 watts (this is the input

Efficiency= 100*(output/inpu)t=(1078.419/1800)*100=59.9

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