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Voltage and resistance

  1. Dec 15, 2014 #1
    recently, I did a experiment about insulating coating on a powder.

    and I measured resistance with various voltage.

    according to Ohm's law, the resistance is constant

    however, my sample showed different resistance with difference V.

    At every voltage, I checked the currents and the resistance and their multiplies(I*R) show same voltages.

    Is it possible that resistance changes?

    Please, explain me if anyone can...
    Last edited by a moderator: Dec 22, 2014
  2. jcsd
  3. Dec 15, 2014 #2


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    Can you post your raw data? V, i, R?
  4. Dec 15, 2014 #3


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    It is possible. Take a look a the IV curve for a diode. At different voltages the slope of the curve changes.
  5. Dec 15, 2014 #4
    Even for a simple wire, Ohm's law won't always hold. As you increase the current and voltage, at some point the I-V curve will become non-linear due to the wire heating up.
  6. Dec 15, 2014 #5


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    Ohm's law actually stipulates constant temperature. People confuse Ohm's Law with the simple formula for Resistance (=V/I). There is a distinct difference, of course.
  7. Dec 15, 2014 #6
    The temperature should be constant. I did not clearly understand your experiment, more detail please ?
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