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Homework Help: Potential difference between Bird's Feet?

  1. Sep 22, 2007 #1
    1. The problem statement, all variables and given/known data

    A bird sits on a high-voltage power line with its feet 2.0 cm apart. The wire is made from aluminum, is 3.0 cm in diameter, and carries a current of 160 A. What is the potential difference between the bird's feet?

    2. Relevant equations


    Where I is current, n is electrons per volume, A is cross sectional area, v is drift velocity.


    3. The attempt at a solution

    My answer is going to have units of J/C, and the cross sectional area of the wire is 1/4*Pi*(3cm)^2.

    I don't know where to proceed from here.
  2. jcsd
  3. Sep 22, 2007 #2


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    Is there anyway you can find the resistance of the wire, maybe using the area and the fact that it's made out of Aluminum?
  4. Sep 22, 2007 #3
    Thanks for helping me. Yes, I can find the resistance:

    R = p*L/A
    = p * (2 cm)/A

    Where p for Al is 2.82E-8 ohms*m, A is the cross sectional area, 1/4*Pi*(3 cm)^2

    Where to go from here?


    Oh wait a second, I = V/R so I*R=V. Is that it?
    Last edited: Sep 22, 2007
  5. Sep 23, 2007 #4


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    You're a good part of the way there. We want to know the potential difference between the bird's feet. You have the current given in the problem. How would you find the resistance involved?
  6. Sep 23, 2007 #5


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    Yes, once you calculate the resistance, Ohm's Law would be the way to go.
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