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Homework Help: Proving Ohm's Law between 2 circuits

  1. Feb 13, 2012 #1
    1. The problem statement, all variables and given/known data
    Hello guys. I've ran into this conceptual problem. I was given into physic's lab to prove Ohm's law by mounting a circuit in two ways, and calculate both Voltage and Intensity.

    The first circuit, the A (Please refer to Circuit A.jpg), has the inconvenient in which the ammeter does not measure the current (I) which passes through the resistance *(R), but the total intensity (I) of the circuit.

    The second one, the B (Please refer to Circuit B.jpg), has the inconvenient in which the voltmeter does not really measure the potential difference between the ends of the resistance, but between the ends of the association of resistance in series with the ammeter:

    They should give me the same. Problem is, the results between circuit A and circuit B gave me different, and I must know why. The teacher said something about the resistance, but it didn't quite grasp what he said. I'm recurring here for help, any ideas?

    Thanks a lot in advance.

    P.S.: I've left you the results from Circuit A and B. They both were done by making the Voltage as the independent variable.

    2. Relevant equations


    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Feb 13, 2012 #2


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    Gold Member

    what are your units for current? A, mA, uA, nA?

    most of the time I would say that has something to do with the finite resistance values of you voltmeter and ammeter, but if your current values are measured in whole amperes then you probably have other problems as well, or your equipments are particularly lousy...
  4. Feb 13, 2012 #3
    Thanks for the quick reply.

    Sorry for not posting the units! But yest, they are measured in Ampere (A).

    Being the lousy equipment could be a very big possibility, since I don't believe they are taken good care of them.
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