Energy Activity Sheet 3 Name:_______
How powerful are you?
In Activity 1 when we calculated work we didn’t use the time it took you to run up the stairs. You will do the same amount of work if you walk or run up the stairs, but walking will take longer. We need the time you took so we can calculate your power.
Power is the rate at which work is done.
In the previous worked example, the student did 4,800 joules in 15 s. So, she did 300 joules in each second, on average. Her power (we call it P) was
Power = work/time
P = W/t = (4,800 J)/(15 s) =
320 joules per second = 320 watts.
A joule per second is called a watt, and it is the standard unit of power. A watt is a small unit – you can produce hundreds of them – so quite often you will see kilowatts for domestic appliances and megawatts (a million watts) or gigawatts (a billion watts) for power stations. The symbol for a watt is W and for a kilowatt kW.
Your Calculations
So how powerful are you?
Do your calculation here. Take the work and time calculation from Activity Sheet 1
P = W/t = (_______ J) / (_______ s) = ____ joules per second
= _______ watts.
Electrical power
In the example above, we looked at power as the rate at which chemical food energy was turned into mechanical work – stair climbing. Watts are used to measure the rate at which we use or produce any sort of energy: chemical, mechanical, electrical and thermal.
Now Calculate
How many watts of power did you generate while going up the stairs?
How many 100-watt light bulbs could you light with this amount of power?
(Divide 100w light bulb by 320w student power = I student can power 3.2 bulbs)
Choose 5 appliances from the appliance power rating resource sheet and work out how many students it would take to run them. Each member in the group must choose different appliances.
1. Name of appliance: _______________ Typical power rating: _______
Calculation:___________________________ No of students: ______
2. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
3. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
4. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
5. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
Credits
Activity Sheet 3 modified with materials from Glimpses of Science (Connor, etal, 2010), and Click 2 (Origin Energy,2010).
How powerful are you?
In Activity 1 when we calculated work we didn’t use the time it took you to run up the stairs. You will do the same amount of work if you walk or run up the stairs, but walking will take longer. We need the time you took so we can calculate your power.
Power is the rate at which work is done.
In the previous worked example, the student did 4,800 joules in 15 s. So, she did 300 joules in each second, on average. Her power (we call it P) was
Power = work/time
P = W/t = (4,800 J)/(15 s) =
320 joules per second = 320 watts.
A joule per second is called a watt, and it is the standard unit of power. A watt is a small unit – you can produce hundreds of them – so quite often you will see kilowatts for domestic appliances and megawatts (a million watts) or gigawatts (a billion watts) for power stations. The symbol for a watt is W and for a kilowatt kW.
Your Calculations
So how powerful are you?
Do your calculation here. Take the work and time calculation from Activity Sheet 1
P = W/t = (_______ J) / (_______ s) = ____ joules per second
= _______ watts.
Electrical power
In the example above, we looked at power as the rate at which chemical food energy was turned into mechanical work – stair climbing. Watts are used to measure the rate at which we use or produce any sort of energy: chemical, mechanical, electrical and thermal.
Now Calculate
How many watts of power did you generate while going up the stairs?
How many 100-watt light bulbs could you light with this amount of power?
(Divide 100w light bulb by 320w student power = I student can power 3.2 bulbs)
Choose 5 appliances from the appliance power rating resource sheet and work out how many students it would take to run them. Each member in the group must choose different appliances.
1. Name of appliance: _______________ Typical power rating: _______
Calculation:___________________________ No of students: ______
2. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
3. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
4. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
5. Name of appliance: _______________ Typical power rating: ______
Calculation:___________________________ No of students: ______
Credits
Activity Sheet 3 modified with materials from Glimpses of Science (Connor, etal, 2010), and Click 2 (Origin Energy,2010).
| energy_activity_sheet_3.doc |
