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Current Source in Parallel with Short Circuit

  1. Dec 13, 2014 #1
    1. The problem statement, all variables and given/known data

    Which of the following are self-contradictory combinations of circuit elements?

    - A 2 Amp current source in parallel with a short circuit.

    2. Relevant equations

    KVL- "the sum of voltages around a closed loop amounts to 0.
    KCL- "the current into a node equals the current out of a node.
    Ohm's Law- V= IR

    3. The attempt at a solution

    The answer key says this is not contradictory, but I don't see how we can have such a circuit... If we had a short circuit parallel to a current source wouldn't all the current go into that short circuit branch and ignore the other branches? Then we'd just have a loop of 2 Amp current with no voltage drop... Why wouldn't that violate KVL?
     
  2. jcsd
  3. Dec 13, 2014 #2

    ehild

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    An ideal current source provides a given current no matter what the load is. The voltage across it is equal to the generator current multiplied by the loading resistance, zero for a short-circuit. Where is contradiction?
     
  4. Dec 13, 2014 #3

    Bystander

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    What are the other choices you're given?
     
  5. Dec 13, 2014 #4
    I just always thought that in order for current to flow between two points we need a voltage difference...

    I understand the rest of them... It was only this one I was hung up on
     
  6. Dec 14, 2014 #5

    ehild

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    What is the voltage difference across zero resistance according to Ohm's Law?
     
  7. Dec 14, 2014 #6
    V=IR so V=I*0=0. Ok I think I see now
     
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