Due: Monday 4/21/2003

Questions and Problems

Chapter 3.

Question:

1. What is the difference between "energy conservation" and "conservation of energy"? Give an example of each.

Problems (see text for energy conversion factors):

2. How many pounds of coal has the same heating value as 20 gallons of gasoline?

3. If a coal-burning electrical plant burns 2 tons of coal to generate 6000 kWh of electricity, calculate the efficiency of the plant as the ratio of electrical energy output to fuel energy input (see Table 3.4).

Chapter 4. Questions:

4. Why can't a body contain heat?

5. Is it possible to increase the temperature of a gas in a cylinder without any energy transfer as heat? Explain.

6. Illustrate all three methods of heat transfer from a woodburning stove. Use a sketch to explain.

Some practical problems:

7. How much electrical energy (in kWh) is needed to heat the water in a well insulated hot tub of capacity 240 gallons from 15 degrees C (59 F) to 38 degrees C ? (100.5 F)

8. If electricity costs $0.08 per kWh, how much does it cost to heat the water?

9. An electrically operated hot water heater contains 40 gallons of water. The heater consumes 4 kW of electricity. How long will it take to heat the water from 60 degrees F to 120 degrees F?