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Homework Help: Calculating diamter of wire that will blow if current exceeds 1A

  1. Mar 5, 2010 #1
    Calculating diamter of wire that will "blow" if current exceeds 1A

    1. You need to design a 1.0 A fuse that "blows" if the current exceeds 1.0 A. The fuse material in your stockroom melts at a current density of 500A/cm^2.



    2. J = I/A



    3. J = 500A/m^2 = 50000A/m^2 = 1.0A / (pi*r^2)

    r = sqrt[1/50000*pi] = 0.00252 m
    diamter = 2*r = 0.005 m = 5.0mm

    That is incorrect (answer in mm).
     
  2. jcsd
  3. Mar 5, 2010 #2

    tiny-tim

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    Hi Linus Pauling! :smile:

    (try using the X2 tag just above the Reply box :wink:)

    You didn't use enough zeros to convert from cm2 to m2 :wink:

    (but why bother? why not leave it as cm??)
     
  4. Mar 5, 2010 #3
    Re: Calculating diamter of wire that will "blow" if current exceeds 1A

    ahh cripes. thanks for the catch... i always do that. :)
     
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