1. Everyday examples of the Joule the energy required to lift a small apple one meter straight up. the energy released when that same apple falls one meter to the ground. the energy released as heat by a quiet person, every hundredth of a second. the energy required to heat one gram of dry, cool air by 1 degree Celsius. one hundredth of the energy a person can receive by drinking a drop of beer. the kinetic energy of an adult human moving a distance of about a hand-span every second.

2. Power Power: the rate at which work is performed – Or, the rate at which energy is transmitted – Or the amount of energy expended per unit time Measured in Watts: Other units: – HP or horse power – BTUs

3. Horse power Arose as a result of the invention of the steam engine. People needed a way to compare the power of a steam engine to that of the horses it was replacing. Confusing unit there are too many different definitions!

4. BTU BTU: British Thermal Units - an energy unit – the amount of heat required to raise the temperature of one pound of liquid water by one degree from 60° to 61°Fahrenheit at a constant pressure of one atmosphere Used in the power, steam generation, heating and air conditioning industries and the energy content of fuels. However, BTU is often used as a unit of power, where BTU/hour is often abbreviated BTU. – So you need to watch the context!

5. Back to Watts….. A human climbing a flight of stairs is doing work at a rate of about 200 watts. A typical household incandescent light bulb uses electrical energy at a rate of 25 to 100 watts, while compact fluorescent lights typically consume 5 to 30 watts. A 100 Watt light bulb consumes energy at the rate of 100 joules/second. After 1 hour, this light bulb uses 100 watt-hours 1 kilowatt (kw) is 1000 Watts

6. Examples In a certain room in your house, you use a 100 W light bulb. This light is on for 5 hours every day. How much energy does it use? 1 W = 1 J/s and there are 5h x 60min/hour x 60 sec/min = 18,000s in 5 hours so the total energy used is 100 j/s *18000s = 1.8 x 10 6 J. Lets assume the same lighting level can be achieved using a 30 W compact florescent bulb. How much energy is used by the compact florescent bulb?

7. Examples Total energy = 30 j/s x 18000 s = 5.4 x 10 5 j. So how much energy is saved every day using the compact florescent bulb? Take the difference between the energy used by the two different light bulbs: 1.8 x 10 6 j - 5.4 x 10 5 j = 1.3 x10 6 j. Lets look at this in something you might be able to relate to better than joules---dollars!

8. Example continued After 5 hours, our 100 W light bulb uses 500 Watt-hours, or 0.5 Kwh. The 30 W bulb will use 150 Watt hours or 0.15 Kwh. Assume electricity costs 11 cents/Kwh (average cost in the US in April 2008). So it costs.5 KwH x 11 cents/Kwh = 5.5 cents every day to run the 100 W light bulb and 0.15Kwh x 11 cents = 1.65 cents every day to run the compact florescent.

9. Example continued So in a year, the 100 W light bulb costs you 5.5 cents/day X 365 days/year = $20.00 and the 30 W bulb costs costs you 1.65 cents/day x 365 days/year = $5.50.

10. Types of Energy: kinetic and potential Energy Kinetic energy - energy of a moving object KE=1/2mv 2 Potential Energy – Energy stored in a system, for example an object of mass m, a distance h above the surface of the earth has a potential energy given by mgh. g is the acceleration due to gravity = 9.8 m/s 2

11. More examples of potential energy Another example is a spring, compressed a distance x from its equilibrium point has a potential energy 1/2kx 2, where k is the spring constant, a property of the spring.

12. Chemical Energy Energy that is released via chemical reactions. Often times release is through combustion such as energy generation via coal Another example is a battery

13. Heat Energy Temperature Scales: Fahrenheit – based on the height of liquid (often mercury or alcohol) in a glass tube. Celsius – another scale using height of liquid in a tube Kelvin-absolute scale – True measure of energy Energy associated with the random motions of the molecules in a medium. Measured by temperature

14. Fahrenheit temperature scale Freezing point of water set at 32 and boiling point set at 212, so there is 180 degrees between them and each degree is 1/180 of the difference between these two points.

15. Celsius temperature scale Freezing point of water set at 0 and boiling point set at 100, so there is 100 degrees between them and each degree is 1/100 of the difference between these two points.

16. Kelvin temperature scale O k is absolute zero. All molecular motion stops. Interval set so that 1 k = 1 c So to convert from c to k k=c+273

17. Mass Energy E = mc 2 Energy and mass are equivalent C = 3 x 10 8 m/s. A big number and its squared! So even if m is small, E is big. A small mass, converted to energy, gives a lot of energy!

18. Example