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Resistance or current

  1. Apr 25, 2015 #1
    resistivity.png
    Should not there be R (resistance) instead of I (current)in the last line i.e
    I ∝ m/a^2
     
  2. jcsd
  3. Apr 25, 2015 #2

    mfb

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    Probably.
     
  4. Apr 25, 2015 #3
    If this is an electrical question, there's something missing from that final line....
     
  5. Apr 25, 2015 #4
    Yes,It is.
     
  6. Apr 25, 2015 #5
    What's that?
     
  7. Apr 25, 2015 #6
    The answer is actually very similar to the one I posted in your previous thread...

    I'm trying not to just give it away. Here's a hint: review Ohm's Law
     
  8. Apr 25, 2015 #7

    mfb

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    It is a "proportional to" sign in the last line. It is a weird way to express the proportionality, however.
     
  9. Apr 25, 2015 #8
    Very true; I'm just not a fan of expressing a current-to-resistance proportionality without a requirement that "voltage remains constant".

    To better answer the OP's question:
    Assuming voltage remains constant, resistance and current are inversely proportional to each other
    Assuming the physical makeup of the conductor remains the same, cross-sectional area an resistance are inversely proportional to each other
    Therefore, assuming voltage and physical makeup of the conductor remain the same, current and cross-sectional area of the conductor are directly proportional
     
  10. Apr 25, 2015 #9

    sophiecentaur

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    There's something I am not getting about the OP. The symbol ρ is commonly used for Resistivity and also for Density. It strikes me that the two appear to be used interchangeably in the attachment. I don't see the logic of the argument being used in that attachment. Can someone explain. please?
     
  11. Apr 25, 2015 #10
    Maybe she can provide more context. Is that from the internet?
    Without context looks like a bizarre relationship.

    They seem to use d for density and ρ for resistivity.
     
  12. Apr 26, 2015 #11

    sophiecentaur

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    @gracy
    It is often possible to take two unrelated expressions, then re-arrange them, algebraically, assume that some of the variables in each expression are the same value and get an unexpected apparent relationship between two variables. It can be mathematically correct but of no meaningfulness in terms of the Physics at work. One needs always to be aware of the physical implications of such bits of maths manipulation.
     
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