1. Power

2. Your Utilization of Electricity Have you ever heard the word Watt before? Have you ever used the word Kilowatt before? When? When a person is speaking in terms of Watts they are generally talking about the amount of energy that they are using.

3. Power Power is a measure of your energy consumption Power is measured in watts You can calculate power using the following formula P = I V P – power (W) I – current (A) V – voltage (V)

4. Voltage Amount You will notice that the voltage for a given question will often not be supplied. Why do you think this might be? Where is the source providing voltage in most situation in your home? What is the voltage of this? This means that when voltage is not supplied for you the assumed amount is always “120V”.

5. Example 1 How much current is running through a 100 watt light bulb? P = 100 w V = ? I = ?

6. I = P / V = 100 W / 120 V = 0.83 A

7. Example 2 How much current is required to operate a DVD player that uses 1200 watts of energy?

8. P = 1200 W V = 120 V I = ? I = P / V = 1200 W / 120 V = 10 A

9. The Cost of Electrical Energy Electrical energy is required to operate electrical apparatuses. The cost of electrical energy is calculated using the following formula. E = P x t E = amount of electrical energy used in kilowatt-hours P = power (kilowatts) T = time (hours)

10. To calculate the cost to operate an electrical device you need to multiply the amount of energy consumed by the price of a kilowatt-hour. The cost of a kilowatt-hour that we are going to use is 9.11 cents / hour.

11. Watt – Kilowatt Conversion Most electrical devices have a power consumption measured in “Watts”. In order for us to calculate the cost we need to know “Kilowatts”. How many watts are in a kilowatt? There are 1000 watts in 1 kilowatt. This means we need to divide by 1000 to convert watts to Kilowatts.

12. Example 1 Spencer played his playstation game for 8 hours last weekend. The playstation uses 160 W of energy and the television uses 200 W of energy. Calculate the cost to operate this system.

13. t = 8 h P = 160 W + 200 W = 360 W = 0.36 KW E = ? E = P t = 0.36 KW x 8 h = 2.88 KWh C = E x 9.11 ¢ = 2.88 KWh x 9.11 ¢ = 26. 24 ¢

14. Example 2 Mr.Hopper uses his 400 W projector for 2 hours each day for 30 days. Calculate the cost to run the projector.

15. t = 60 h P = 400 W = 0.4 KW E = P t = 0.4 KW x 60 h = 24 KWh C = E x 9.11 ¢ = 24 KWh x 9.11 ¢ = 218.64 ¢ = $2.19

16. Example 3 A blender operates using 15 amps of current and 240 V. If the blender is used for 3 hours calculate how much that would cost.

17. P = I V P = 15 A x 240 V = 3600 W = 3.6 KW t = 3h I = 15 A V = 240 V E = P t = 3.6 KW x 3 h = 10.8 KWh C = E x 9.11 ¢ = 10.8 KWh x 9.11 ¢ = 98.39 ¢