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The Rate at which kinetic energy changes to thermal energy

  1. Apr 14, 2013 #1
    A potential difference of 50 mV is maintained between the ends of a 9.70 m length of wire whose cross section area is 25.0mm^2. The conductivity of the wire is 6.80 x 10^6 (ohm.m)^-1. Determine the rate at which the energy in the wire is transformed into kinetic to thermal energy.

    2. Relevant equations
    P = v^2/R

    ρ = 1/c

    R = ρ (L/A)

    Where ρ = resistivity
    c = conductivity
    A = area
    L = length
    R = Resistance
    V = Voltage
    P = power


    3. The attempt at a solution

    ρ = 1/6.80 x 10^6 = 1.471 x 10^(-7)

    R = 1.471 x 10^(-7) * ( 9.70/0.000025 )
    = 0.0570748
    P = (50 x 10^-3)/0.0570748
    = 0.0438021
    = 4.38 x 10^(-2) W

    This is my complete work. I think my workings are correct but My instructor says my answer is wrong. I will be glad if anyone can help.
     
  2. jcsd
  3. Apr 14, 2013 #2

    mfb

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    Where do you have kinetic energy? I think this should be electric energy.

    There is a ^2 missing at P=, but the following line is correct. Units are missing everywhere :(.
    I would express the final answer in mW or W. I agree with the result, however.
     
  4. Apr 14, 2013 #3

    haruspex

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    This is a duplicate of post https://www.physicsforums.com/showthread.php?t=685309, 1 hour earlier, apparently just to change the title.
    As mfb says, there's is no kinetic energy involved here, unless you mean thermal energy viewed as kinetic at the atomic level.
     
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