Measuring Heat..?

Question

1. The power of a coffe pot is rated at 900 watts. It can heat 1 liter of water in 2 minutes.

a) How much electrical energy does the coffee pot use in this process?

b) Assuming the coffee pot has an efficiency of 30%, how much of the electrical energy cecomes thermal energy in the water?

c) What is the increase in the temperature of the water?


2. Two beakers each contain 1 kg of water at 0°C. One kg of gold at 100°C is dropped into one beaker. One kg of aluminum at 100°C is dropped into the beaker.

a) Compare the amount of thermal energy contained in the aluminum and gold

b) After each beaker has reached thermal equilibrium, describe whether the temperatures are the same, or different. If they are different, describe which is warmer and which is colder.

c) Explain why you have your answer to part (b). Use the concept of specific heat in your explaination.


DO NOT SAY "DO YOUR OWN HOMEWORK" OF ANYTHING OF THAT NATURE.

Answer 1

For the first question, think about how power is related to energy. Power is the energy flow per unit time. Once you find the electrical energy used by the coffee pot, both parts b and c are trivial.

For part 2a, think about how thermal energy and temperature relate. What is temperature a measure of?

For part 2b, think about how energy transfers from one substance, like gold, to another water. What does "thermal equilibrium" mean?

Part 2c gives you a clue how you should do part 2b, you have to use the specific heat of water, gold, and aluminum somewhere.

Good luck.