1. ENERGY

2. Energy  Energy is measured in Joules (J)  A joule is a small unit of energy NOT JEWELS like these -> JOULES

3. Energy  The amount of energy used over time is called POWER.  When describing POWER, we use Watts (W) 1 W = 1 Joule second

4. Energy  Watts are convenient to use for small things like light bulbs or laptops. However, energy used by larger devices may be described using kiloWatts (kW) 1 kW = 1000 W = 1000 Joules second

5. Energy  For devices that require large amounts of energy over a long period of time, like a house, one may use kiloWatt hours (kW ● h)  1 kW ● h = 1000 W ● h = 1000 Joules x hour second

7. Efficiency  An electric kettle is supplied with 100 000 J of energy and produces 90 000 J of useful heat energy. What is the efficiency of the electric kettle?

8. Percent Efficiency  A man uses 150 J of energy moving a box up a steep slope. The amount of work produced is 37.5J. What is the percent efficiency of the man pushing the box?

9. Watts, kiloWatts and Joules  A 55 inch plasma television uses 507 W when displaying High Definition TV.  What is the tv’s power use in kiloWatts?

10. Watts, kiloWatts and Joules  A 55 inch plasma television uses 507 W when displaying High Definition TV.  How much energy does the TV use when watching TV for 30 minutes?

11. Cost of Electricity  In Toronto, electricity costs $0.074 / kWh. An electric heater uses 2 kW every hour. How much would it cost to leave this heater on for 2 hours and 30 minutes?

12. YOUR TURN