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Equation of resistance

  1. Apr 7, 2012 #1
    Voltage(V) is proportional to current(I). And so V=(a constant)*I. That constant is known as resistance(R), where R=V/I. Why can't we write that I proportional to V and then write R=I/V??
  2. jcsd
  3. Apr 7, 2012 #2


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  4. Apr 8, 2012 #3


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    We write G=I/V
    and the units of G used to be known as mhos (that's Ohms spelled backwards) with symbol an upsidedown Ω (omega).

    Nowadays, the units have been renamed an uninteresting "siemens". :frown:
  5. Apr 8, 2012 #4
    Because that is not the reality? I know VR != I. If that were the case, current would increase with resistance. Which completely disagrees with our current definition of resistance!

    Oh, I misinterpreted your post. Well, yes, of course you could. But R would be a different quantity, as the right side of the equation implies.
    Last edited: Apr 8, 2012
  6. Apr 12, 2012 #5
    Could you please make it clear???
  7. Apr 12, 2012 #6


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    Resistance (R) is DEFINED to be what it is. There is no "reason" for it, it is just a convention.

    And again, the quantity I/V already has a name of its own: conductance (G), which has the units of Siemens.
  8. Apr 12, 2012 #7


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    I think you means 1/R.

    Remember: R is 'how hard'
    and G is 'how easy'.
  9. Apr 12, 2012 #8
    Thanks f95toli.. i think your answer is quite satisfying for me.....
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