Post on 23-Feb-2016
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Measuring Energy Part 1Newtons, Joules, Watts
Energy Use in Canada• Canadian households used 1,425 petajoules of
energy in 2011 (StatsCan)• 1 petajoule is approximately the amount of
energy needed to run the TTC subway for one year
Newton (N)• SI unit of FORCE– Force is a push or pull against an object
• 1 Newton is the amount of force needed to accelerate a mass of 1 kg by 1 meter/s2
N = kg x m/s2
A newton will move 1 kg of weight• one meter in the first second, • 2m in the second second• 3m in the third second
Newton (N)
Time 1 Second 2 Seconds 3 Seconds
1 KG
1 KG 1 KG
1 KG1 KG
1 KG
Joule (J)• SI unit of energy and work – Energy is the ability to do work– Work is the energy transferred when a force moves an object
• 1 joule is the work done/energy transferred when 1 newton of force moves an object 1m.
J = N x m (N=newton, m=meter)
One joule equals the energy needed to lift an apple from the floor to the tabletop, about 1m.
Watt (W)
• The SI unit of power– Power is the rate at which work is done
• One watt is equal to 1 joule of energy produced per second
W = J/s(j=joule, s=sec)
Watt hours (Wh)• Light bulbs are rated according to the power they
use• this is measured in Watt hours (Wh).
Since there are 3600 (60 x 60) seconds in an hour
one watt hour = 3 600 joules of energy
• A 20 watt lightbulb uses 20 watts of power in an hour. – A 20 watt bulb uses 3 600 X 20 = 72 000 joules of energy
Kilowatts (KW)
• 1000 Watts is a kilowatt (KW)
• A kilowatt hour (KWh) is equal to 1000 watt hours (Wh)
One KWh = 1000 watt hours
1000 watt hours = 1000 x 3 600 = 3 600 000 joules