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Why do we need two wires for electricity?

  1. Nov 22, 2014 #1
    I know the circuit must be complete in order for devices to work. I want to understand this with an analogy in reference of a battery. Let there be a bulb in the circuit connected to a battery. Now if circuit is closed then what happens in the circuit? Electrical energy lights up the bulb so is there any loss of electrons in numbers or is it electrons lose kinetic energy when they are returned to the positive end.
     
  2. jcsd
  3. Nov 22, 2014 #2

    nsaspook

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  4. Nov 23, 2014 #3
    Think of the electrons in the wire like a bike chain and the power source is like the pedals. When you do work on the pedals, you pull the chain, and the work is done on the rear wheel.

    The electrons, like the chain, let the power source do work on the load (in your case, a light bulb).

    Now, the reason we need two wires is that to make those electrons move they need to use up potential energy. The positive terminal is high potential (has more potential energy) and the negative is low (or ground, which may or may not literally be the ground) potential. The electrons want to go to from the high potential to the low potential, but to do that they need a conductor. Work is done by a system when it uses up potential energy, so the electrons do work when they use up potential energy in moving from high potential to low potential.
     
  5. Nov 23, 2014 #4
    Current is driven through a wire by an electric field. If the circuit is not closed charge will accumulate which produces an opposing field reducing the field strength in the wire to zero.
    http://www.phy-astr.gsu.edu/cymbalyuk/Lecture16.pdf [Broken]
    http://www.astrophysik.uni-kiel.de/~hhaertel/PUB/voltage_IRL.pdf [Broken]
     
    Last edited by a moderator: May 7, 2017
  6. Nov 23, 2014 #5

    davenn

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    except the electrons move from negative to positive ;)

    be careful with your conventional and electron flow directions :)

    Dave
     
  7. Nov 26, 2014 #6

    analogdesign

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    The electrons move from negative to positive, the current flows from positive to negative. Damn you Benjamin Franklin!
     
  8. Nov 26, 2014 #7

    nsaspook

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    We now know the true mission of "Interstellar".
    urgent_mission.png
     
  9. Nov 26, 2014 #8

    analogdesign

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    haha that's awesome. Never saw that one.
     
  10. Nov 30, 2014 #9

    sophiecentaur

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    If that presents a problem for anyone then they can't claim to have a proper grasp of electricity. It's irrelevant (could be African or Indian :D).
     
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