1. Lecture Seventeen Physics 100 Fall 2012  Electric Power and Energy

2. Watt x hour or a kilowatt-hour is a unit of energy which can be converted into a Joule.

3.  The Watt-Hour or W·hr is a unit of energy.  This makes sense because it is a unit of power (the watt) multiplied by a unit of time (an hour).  If you operate a 1 watt device for 1 hour you use 1 watt-hour of energy.  If you operate a 60 watt light bulb for 2 hours you have used 120 watt-hours of energy.

4.  The kilowatt-hour (kW·hr) is also a unit of energy.  It is 1000 (kilo) watt-hours.  If you run a 100 watt bulb for 10 hours you use 1000 watt-hours or 1 kilowatt-hour of energy.  You electric bill is typically written in terms of kilowatt-hours.  A typical rate for electricity in the US is 12 to 17 cents per kilowatt-hour.

5. And because V=iR

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