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Chapter 11Using Electricity
11.1 - Work, Energy and PowerWork - transforming or converting of energy
Energy
An object has energy (E) it has the ability to do work
Two main types:
Energy that is stored
Potential Energy (PE)
Kinetic Energy (KE)
Energy of an object in motion
Work = Change in Energy
Law of Conservation of Energy
In any closed system, the total amount of energy remains constant
When all types of energy are added up, the total NEVER changes, no matter what!
Power
Power is the rate at which energy is transformed (or rate at which work is being done)
Measured in watts (W). 1 W = 1 J/s
remember that so …..
Homework: Read 11.1 in your textbook and do the following questions pg. 339 - # 4 - 9
11.4 - Household Electrical Energy
The History of the Electrical Power Industry
Before electricity:
Lamps fuelled by natural gas and oils
Gaslights used to light streets
First lightbulb:
1879 - Edison
First power plant:
1882 - New York100 V; DC - needed large currents, gave low power
AC electricity
Tesla/Westinghouse - allowed transmission of higher power electricity
The Electric Meter
We know that: ΔE = P x (Δt)
Usually, E is in Joules (J).For measuring electricity usage, it is kWh (kilowatt hour)
Number of Joules is too large, so kWh is used.