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Electricity & Magnetismat Work
Using Electric Power
Chapter 3
Section 3
Electric Power
• The rate at which energy is converted from one form into another.
• James Watt– 1700’s– Designed Steam Engines
Power Ratings
• Stove = 6,000 W• Clothes Dryer = 5,400 W• Water Heater = 4,500 W• Washing Machine =
1,200 W• Dishwasher = 1,200 W• Hair Dryer = 1,200 W• Iron = 1,100 W• Microwave = 1,000 W• Coffee maker = 1,000 W
• Toaster = 850 W• Food Processor = 500 W• Fan = 240 W• TV = 100 W• Clock radio = 12 W
Calculating Power
• Power = Voltage x Current• Watts = Volts x Amps
Power Problem
• A household light bulb has approximately 0.5 amps of current flowing through it.
• Since the standard household voltage is 120 V, what is the power rating of the light bulb?
• P = V x A
Paying for Energy
• Energy = Power x Time • Kilowatt-hour– kWh
• ~$0.10 each
High Voltage Power
• 10,000 - 800,000 V– More efficient for long
distance conduction
• House Appliances– Use 120 V
Transformers
• A devise that increases/decreases voltage
• Primary Wire induces a current onto a secondary wire– Step Up Transformer– Step Down Transformer
Hans Christian Oersted
• 1820– Electromagnetism
• Discovers that an electric current creates a magnetic field
Michael Faraday & Joseph Henry
• 1830– Electric Induction
• Discover that an electric current can be induced by a changing magnetic field
Thomas Edison
• 1882– Opens his first DC
electric producing power plant in New York City.
– It provided 120 V to 2.6 square kilometers of customers.
Nikola Tesla
• 1888– Received patents for
distributing power via high voltage AC, using step up/down transformers
Nikola Tesla
• 1893– AC is used to power
the World’s Fair in Chicago