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I Origin of Ohm's law

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  1. Aug 27, 2016 #1
    Hi everyone,

    My question is about the origin of ohm's law, how it was discovered. Ohm's law is pretty simple and I don't have any problems using it. My real problem is understand how it was discovered. I was able to find a translated book of Georg Ohm ("The Galvanic Circuit Investigated Mathematically"), but this book makes no sense to me at all. I couldn't even find his famous equation in that book. I know that by the 1800's they were able to measure current using tangent galvanometers and other instruments. I would like to know what experiments were conducted to conclude E = IR. Thanks.
     
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  3. Aug 27, 2016 #2

    Grinkle

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  4. Aug 27, 2016 #3
    That link did not answer my question. Please read my question carefully. I am asking for the origin and the experiments that were conducted. I am pretty sure in Ohm's time there was no digital multimeter.
     
  5. Aug 27, 2016 #4

    davenn

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    HUH ?? I didn't even see a mention of digital multimeter ... did you actually read the link ?
     
  6. Aug 27, 2016 #5

    phyzguy

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  7. Aug 27, 2016 #6

    davenn

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  8. Aug 28, 2016 #7
    I did actually read the link and in the link there were other links to experiments, and in those experiments they used a multimeter.

    GUYS are you reading my question or not. I already told you I read his book and no where in there did he mention E = IR, or any experiments he conducted that lead him his equation. Why are you sending me a link to the English translation of his book? I already have it.

    I'll state my question in another way. I want to know the experiments that Ohm conducted, and I mean exact experiments. What instruments he used, and a result of those experiments. Then from the results, how he proved E = IR.
     
  9. Aug 28, 2016 #8

    phyzguy

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    It certainly doesn't seem like you've read Ohm's original paper. You say he doesn't mention E = IR, but the paper specifically says, "The magnitude of the current in any homogeneous portion of the circuit is equal to the quotient of the difference between the electrical forces present at the extremities of this portion divided by its reduced length."
    In other words, I = E / R, where it is understood that the resistance of a length of wire is given by it's "reduced length", which he describes in detail. To know exactly what experiments he performed, you would need to look up reference [2] which he refers to where he says, "The former I had already some time ago derived from manifoldly varied experiments[2] with an apparatus which allows of an accuracy and certainty of measurement not suspected in this department; the latter expresses all the observations pertaining to it, which already exist in great number, with the greatest fidelity, which also continues where the equation leads to results no longer comprised in the circle of previously published experiments." I'm not going to do this for you - if you are really interested you should look it up yourself. However, he does refer to the use of an electrometer, so I suspect that this is the instrument he used to measure the voltage in the circuits.
     
  10. Aug 28, 2016 #9

    Mark44

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    The question has been asked and answered. Thread closed.
     
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