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KVL loop: Example wrong, or did I misunderstand?

  1. May 27, 2013 #1
    In my circuit analysis textbook, there is an example problem using a KVL loop. Though it seems relatively simple, I cannot understand the answer.

    the loop consists of 3 voltages: -8, 12, and the unknown, Vr2. The polarities (clockwise) around the loop are respectively +,-,+.

    The answer given is 4V for Vr2. I can see this being the case if the 8 wasn't negative, but if I apply algebra, the equation comes out as:

    + (-8) - (12) + Vr2 = 0

    where Vr2 = 20

    Am I treating the -8 wrong? Because if it were positive 8, I could understand Vr2 being 4, however, I am given to understand negative voltage is different from positive voltage.
     
  2. jcsd
  3. May 27, 2013 #2

    SteamKing

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    A circuit diagram would be helpful.
     
  4. May 27, 2013 #3

    Simon Bridge

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    One of those is a voltage source while the other two are the volt drops over resistances huh?
     
  5. May 28, 2013 #4

    CWatters

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    Post the circuit diagram otherwise we are guessing what might be wrong.
     
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