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How does voltage stay the same at all points in a circuit when a resistor is present?

  1. Jul 12, 2012 #1
    Please look at the third circuit diagram from the link below

    http://www.allaboutcircuits.com/vol_1/chpt_2/7.html

    It says that there should be 10V between every point in the diagram. But shouldn't there be a difference in voltage value between points 1 and 2 and points 3 and 4? There's a resistor between points 3 and 4.

    My thinking is that if V=IR and there's a resistor between 3 and 4, it should have a different voltage than between points 1 and 2, which doesn't have a resistor between it.

    Please explain why I am wrong...
     
  2. jcsd
  3. Jul 12, 2012 #2
    Re: How does voltage stay the same at all points in a circuit when a resistor is pres

    It refers to any points 'before' and 'after' the resistor.
    Examples voltage across points 1-4 or 1-6 or 2-5 or 3-6 and any other combinations are equal.
     
  4. Jul 12, 2012 #3
    Re: How does voltage stay the same at all points in a circuit when a resistor is pres

    Voltage refers to a difference in potential energy across two points. It's essentially work done to move a charge between two points. In an ideal wire, there is nothing present to impede the charge from moving freely. I say ideal as real wires have some electrical resistance (superconducting wires do not).

    Anyway, resistors and capacitors change the degree of work needed to move a charge. Resistors make it more difficult for charges to pass through. This creates a potential difference (this term is synonymous with voltage). So the potential energy before the resistor is different from the potential energy after the resistor. Take the difference between these energies and you get the voltage (V = IR).

    Hope this helps.
     
  5. Jul 13, 2012 #4

    CWatters

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    Re: How does voltage stay the same at all points in a circuit when a resistor is pres

    No. Read it again, it doesn't use those exact words it says..

    Basically it's saying that in the sentence

    "The voltage between points 1 and 6 is 10 volts"

    you can:

    Replace "6" with "5" or "4"

    and/or

    Replace "1" with "2" or "3".

    No other combinations measure 10V. For example if you measure beween 2 and 3 you get zero volts.
     
  6. Jul 15, 2012 #5
    Re: How does voltage stay the same at all points in a circuit when a resistor is pres

    Oh wow, I can't believe I missed that...thank you so much!
     
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