1. P1 Energy and Power

2. Title: Energy and Power
DO NOW
Go through your book and find all the equations we have used so far.
Write a list of these on the back red page of your book.

3. Title: Energy and Power
DO NOW

4. Title: Energy and Power
DO NOW
Complete the energy table to show the wasted and useful energy

5. Power
When you turn on an appliance energy is transferred from one form to another. The energy you supply per second is the power The more powerful something is, the faster the rate at which it transfers energy.

6. The equation(s) Power (W)= Work Done(J) / Time (s)
Power (W)= Energy (J) / Time (s)
1 Watt = 1 Joule transferred in 1 second
1W = 1J/s

7. Power (W)= Work Done(J) / Time (s)
Have a go at these…..
What is the power when 300J of work is done for 30seconds?
What is the power when 150J of work is done for 10s?
What is the power when 700J of work is done for 60s?

8. Power (W)= Work Done(J) / Time (s)
Have a go at these…..
What is the power when 300J of work is done for 30seconds? 10W
What is the power when 150J of work is done for 10s? 15W
What is the power when 700J of work is done for 60s? 11.5W

9. Power (W)= Energy (J) / Time (s)
Now these
What is the power when 200J of energy is used for 30seconds?
What is the power when 20J of energy is used for 4s?
What is the energy when 3000J of energy is used for 4 hours (14,400s)?

10. Power (W)= Energy (J) / Time (s)
Now these
What is the power when 200J of energy is used for 30seconds? 6.67W
What is the power when 20J of energy is used for 4s? 5W
What is the energy when 3000J of energy I used for 4 hours (14,400s)? 0.20W
What’s the problem with this?

11. Electrical energy is measured in kilowatt hours. 1 kWh = 3,600,000J
A Joule is a tiny amount of energy, a watt is a tiny amount of power and a second is a short amount time.
Electrical appliances use kilowatts of power
And are usually on for hours, not seconds so....
Electrical energy is measured in kilowatt hours.
1 kWh = 3,600,000J
So, when talking about appliances we use kW for power and hours for time.
Power (kW)= Energy (Kwhr) / Time (hr)

12. Write a homework assignment Computer 0.5 2 hours
Task
Appliance used
Energy (kWhr)
Time for which it is on
Time (hours)
Power in kW
Watch tv TV
1.5
5 hours
Write a homework assignment
Computer
0.5
2 hours
Listen to music
Mp3 player
0.0004
Heat your bedroom
Fan heater
3.0
Wash a load of clothes
Washing machine
2.8
1 ½ hours
Play a video game
PS3
0.19
1 hour
Dry your hair
Hairdryer
0.06
30 mins
Make a pot of tea
Electric kettle
0.13
4 mins

13. Write a homework assignment Computer 0.5 2 hours 2 0.25
Task
Appliance used
Energy (kWhr)
Time for which it is on
Time (hours)
Power in kW
Watch tv TV
1.5
5 hours 5
0.3
Write a homework assignment
Computer
0.5
2 hours 2
0.25
Listen to music
Mp3 player
0.0004
0.0002
Heat your bedroom
Fan heater
3.0
Wash a load of clothes
Washing machine
2.8
1 ½ hours
1.85
Play a video game
PS3
0.19
1 hour 1
Dry your hair
Hairdryer
0.06
30 mins
0.12
Make a pot of tea
Electric kettle
0.13
4 mins
0.16

14. Have a go..... At sheet A (slightly easier) Or
Sheet B (more of a challenge)

15. Just as an aside….you need to know how to convert these back to W
1kW = 1000w
1 MW = 1,000,000W
1mW = 0.001W
1µW = W

16. The same as the other efficiency, just different words
Efficiency and Power.....
The same as the other efficiency, just different words

17. Wasted energy