1. 5.10 Energy and Power  Energy (E) the ability to do work Measured in Joules (J)  Power (P) the amount of work that can be accomplished in a certain amount of time Measured in Watts (W)

2. Energy the ability to do work all appliances need energy to work ex.a hair dryer needs to be plugged in to get energy to work ex.a remote control needs energy from batteries to work What is energy?

3. Power the rate at which energy is used or the amount of work done per second Is measured in Watts  A microwave that uses more Watts will heat food faster! What is power?

4. Symbols and Units Symbol = Units = Symbol = Units =

5. Power Watts (W) Energy Joules (J) Time Seconds (s) E = P x Δt

6. A stereo has a power rating of 200W & is used for 1800 seconds. How much energy is used? E = P x Δt = 200 x 1800 E = 360 000J

7. A video game has a power rating of 175W & is used for 3600 seconds. How much energy is used? E = 630,000 J 630,000 Joules of energy were used to work the video game E = P x Δt = 175 x 3600

8. A hair dryer has a power rating of 425W & is used for 10 minutes. How much energy is used? E = 255,000 J 255,000 Joules of energy were used to work the hair dryer Time must be in seconds 10 min x 60 = 600 seconds E = P x Δt = 425 x 600

9. How do we pay for the energy we use?  Energy can also be measured in kilowatt hours (kWh). If we use 1000W in 1 hour, we consume 1 kWh = 3 600 000 J

10. KWh is used by Hydro Quebec to calculate your energy bill  For a average summer day. Mrs “I” uses 44 kWhs. 30 kWh x $0.0532 = $1.596 14 kWh x $0.0751 = $1.051 $2.647 This is just for ONE day.

11. P = IV Power Watts (W) Current Amps (A) Voltage Volts (V)

12. A toaster requires 120V & 6A to work. What is its power? P = IV P = (6)(120) P = 720 W The toaster has 720 watts of power

13. An appliance requires 240V & 2A to work. What is its power? P = IV P = (2)(240) P = 480 W The appliance has a power of 480 watts

14. An appliance requires 120V & 12A to work. It is used for 900 seconds. How much energy is used? Tricky Question

15. An appliance requires 120V & 12A to work. It is used for 900 seconds. How much energy is used? P = IV P = (12)(120) P = 1440 W Tricky Question E =1,296,000 J E = P x Δt = 1440 x 900

16. An appliance uses 225V & 4A to work. It is used for 1 hour. How much energy is used? P = IV P = (4)(225) P = 900 W Tricky Question E =3,240,000 J 60min x 60 E = P x Δt = 900 x 3600