1. 9.2 The Power of Electricity
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Power
= the rate of change in energy
measured as energy (joules) per second (J/s)
1 J/s = 1 watt (W)
For example:
a 25 W fluorescent bulb converts 25 joules of electrical energy every second into other forms
See pages
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3. Calculating Power & Energy Consumption
Power = Voltage x Current
Energy = Power x Time

4. Paying for Electricity
A Larger Unit for Energy
Homes use LOTS of energy so bigger units are used.
Instead of using watts, use kilowatts
Instead of using seconds, use hours
So, the power company keeps track of kilowatt•hours used.
See page 325
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Converting Units
Try:
525 W = ______________ kW
0.02 kW = _____________ W
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6. Paying Your Power Bill
The power company keeps track of your energy usage by reading your electric meter
To bill you, the power company multiplies how much energy you have used by the cost per kW•h

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What is a kilowatt hour?
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For example:
A 3 kW boiler runs for 30 minutes. How much does this cost if the utility company charges you$0.15/kWh?
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10. Understanding Energy Use
In most homes, electrical energy is measured by smart meters.
Measures how electrical energy use changes in the home over the course of the day
Information gathered is wireless sent
Can track how and when electrical energy is used each day

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Energuide Labels
Government of Canada requires all new electrical appliances be labeled
Gives details about the amount of energy that an appliance uses in one year of normal use
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12. ENERGY STAR® Labels
Identifies a product as meeting or exceeding certain standards for energy efficiency

13. Phantom Loads
Any device that consumes electricity when turned off but still plugged into an outlet.
This wastes energy and cost money.
Can account for approx. 900 kW•h of electrical energy use per year

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Examples:
remote controlled devices
computers
washing machines
microwave ovens
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