Problem: Suppose that you have left a 200- cup of coffee sitting until it has cooled to 30°C which you find totally unacceptable. Your microwave oven draws 1100 of electrical power when it is running. If it takes 45 for this microwave oven to raise the temperature of the coffee to 60°C, what is the efficiency of heating with this oven?1) Which of the following is the quantity you would label as "what you got"?the amount of electrical energy that flows into the oventhe amount of electromagnetic energy (microwaves) that the oven generatesthe amount of heat the oven transfers to the environmentthe amount of heat added to the coffee2) Which of the following is the quantity you would label as "what you had to pay"?the amount of electrical energy that flows into the oventhe amount of electromagnetic energy (microwaves) that the oven generatesthe amount of heat the oven transfers to the environmentthe amount of heat added to the coffee

FREE Expert Solution

The energy input to the microwave oven is given by:

E = Pt = (1100)(45) = 49500 J.

If the efficiency is 100%, it takes 4.2 J to raise the temperature of 1 ml of coffee by 1 °C.

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Problem Details

Suppose that you have left a 200- cup of coffee sitting until it has cooled to 30°C which you find totally unacceptable. Your microwave oven draws 1100 of electrical power when it is running. If it takes 45 for this microwave oven to raise the temperature of the coffee to 60°C, what is the efficiency of heating with this oven?


1) Which of the following is the quantity you would label as "what you got"?
the amount of electrical energy that flows into the oven
the amount of electromagnetic energy (microwaves) that the oven generates
the amount of heat the oven transfers to the environment
the amount of heat added to the coffee


2) Which of the following is the quantity you would label as "what you had to pay"?
the amount of electrical energy that flows into the oven
the amount of electromagnetic energy (microwaves) that the oven generates
the amount of heat the oven transfers to the environment
the amount of heat added to the coffee

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What scientific concept do you need to know in order to solve this problem?

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