SOLUTION: There is 1.5 L of water in a kettle on a cooking plate of 2.0 KW. It takes 7 minutes to heat the water from 20 C to the poiling point. a) How much electrical energy is required ?

Question 388759: There is 1.5 L of water in a kettle on a cooking plate of 2.0 KW. It takes 7 minutes to heat the water from 20 C to the poiling point.
a) How much electrical energy is required ?
b) What is the efficiency of the heating process?!
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
1.5 liters = 1500 grams of water
1500 gm * (100 - 20�C) = 1.2E5 calories
1 watt-min = 14.33 calories
1.2E5/14.33 = 8374 watt-minutes to heat the water
--------------
2000 watts * 7 minw = 14000 watt-minutes
e = 8374/14000 = 0.5981
e =~ 60%

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