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13.3 Alternating Current

13.3 Alternating Current. Alternating Current. An electric current that periodically changes direction Current induction in a coil reverses direction periodically due to having to move the magnet back and forth to keep the magnetic field changing

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13.3 Alternating Current

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  1. 13.3 Alternating Current

  2. Alternating Current • An electric current that periodically changes direction • Current induction in a coil reverses direction periodically due to having to move the magnet back and forth to keep the magnetic field changing • Direct current studied in chapter 11 only works for small circuits. • The transfer of electrical energy using direct current is limited to how far it can be transferred without significant energy loss in the form of thermal energy • Thomas Edison built first power station and was only able to deliver to 193 buildings

  3. What is Alternating Current? • Voltage and Current vs time • Frequency of 60Hz • Current reverses direction 60 times a second • Electrons are essentially in one spot • So fast, we can’t detect it with our eyes

  4. Household Circuits • Apartments and small homes require 50A - 100A of electric current • Larger homes 100A – 200A • Homes are designed to have 240V of service • Electric stoves and dryers are some of the appliance that need this high of voltage. • Other appliances use 120V

  5. Three wire system • Allows to accommodate both 240V and 120V appliances • Red and black = “live” wires or “hot” wires • TheWhite =“neutral” • Voltage between red and black is 240V • Voltage between the red and white or black and white is 120V • Typically electricians use black and white for outlets the require 120V and red and black for outlets that require 240V • Ground wire = green or bare = electrically connected to the ground, preventing stray currents from reaching you, directing them to the ground

  6. Receptacles • 240V service = 3 or 4 prong plugs (one for each wire) • 120V service = 2 or 3 prongs (black, white and green) • Small devices such as lamps may only have two, not having the ground wire • Some devices such as lap tops require direct current and have an adapter within their power cord

  7. Common Household Appliances

  8. Safety • When too much current flows through your circuits… • Fuses: wire in fuse melts and breaks the circuit. Must replace the fuse • Circuit Breakers: Bimetallic strip heats up and bends which “trips” the breaker and turns of the circuit. Reusable and can be reset • Ground Fault Circuit Interrupters (GFCI’s): used in bathroom outlets. Detect difference in current going into the circuit (if you create a circuit by having a wet hand when plugging in an appliance) • Arc Fault Circuit Interrupters (AFCI’s): prevent sparks or arcing if insulation around wire becomes frayed

  9. Homework • Pg 598 #’s 1-6

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