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

Explanation:

Considering the density & specific heat capacity of coffee to be equal to that of water.

GIVEN:

Heat released by the coffee to come to 60°C:

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Now the energy used by the oven in the given time:

Now the efficiency:

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.