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Homework Help: Magnetic field questionwhat did i do wrong

  1. Mar 5, 2006 #1
    4. [SFHS99 21.P.37.] A thin 1.00 m long copper rod has a mass of 50.0 g. What is the minimum current needed in the rod to cause it to float in a magnetic field of 1.00 T?


    i got 4.9 what am i doing wrong i used ma =BiL

    can someone tel me what im doign wrong
     
  2. jcsd
  3. Mar 5, 2006 #2

    Hootenanny

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    I got:

    [tex]mg = BIL[/tex]
    [tex]I = \frac{mg}{BL} \Rightarrow I = \frac{0.05\times 9.81}{1\times 1}[/tex]

    [tex]I = 0.4905 A[/tex]

    Same as you.
    ????? :confused:
     
    Last edited: Mar 5, 2006
  4. Mar 5, 2006 #3
    why do you say the answer is wrong???
     
  5. Mar 5, 2006 #4
    Well, in case it's escaped notice, Hootenanny's answer is 1/10 of kevinlikesphysics'. I'm assuming that kevinlikesphysics simply converted the 50.0 g incorrectly.

    -Dan
     
  6. Mar 5, 2006 #5

    Hootenanny

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    Ahhh, indeed. I miss read. I feel rather stupid now.
     
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