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At what distance from the conductor is the magnitude of the resulting magnetic field

  1. Jul 3, 2009 #1
    1. The problem statement, all variables and given/known data
    A long, thin conductor carries a current of
    8.93 A.
    At what distance from the conductor is
    the magnitude of the resulting magnetic field
    4.79 × 10−5 T? Answer in units of cm.


    2. Relevant equations

    B= Uo*I*l/(2*pi*d)

    3. The attempt at a solution

    i used this equation to figure out the distance but i keep getting the wrong answer
    can someone explain wats going wrong ?!!

    thanx
     
  2. jcsd
  3. Jul 3, 2009 #2

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    What is the l in your equation?
     
  4. Jul 3, 2009 #3
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    its the length
     
  5. Jul 3, 2009 #4

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    Well, the formula is incorrect, which probably explains why you've been getting the wrong answer. How did you arrive at that particular formula?

    As an aside, what have you been using for the length of the wire since the question does not specify how long the conductor is?
     
  6. Jul 3, 2009 #5
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    Oops

    i mixed up the parallel conducters equation with the straight wire equation

    therefore is this the one B=Uo*i/2*pi*d
     
  7. Jul 3, 2009 #6

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    That looks good to me.
     
  8. Jul 3, 2009 #7
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    wrong answer !!

    d=(4*pi*10^-7*8.93)/(2*pi*4.79*10^-5)= 0.011869 this is in meters so i converted it into cm i got 1.1869
     
  9. Jul 3, 2009 #8

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    I'd recheck your arithmetic and make sure that you are punching the numbers into your calculator correctly.
     
  10. Jul 3, 2009 #9
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    i did checked it again but still the same answer
     
  11. Jul 3, 2009 #10

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    Well using your numbers I get a different answer. You must be punching the numbers into your calculator incorrectly.
     
  12. Jul 3, 2009 #11
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    oka i got 13.0501 cm after correct my calculation but still the answer is wrong !!
     
  13. Jul 4, 2009 #12

    Hootenanny

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    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    Still not the same answer as I get. All I can suggest is that you check the manual that came with your calculator to ensure that you are entering the numbers correctly.
     
  14. Jul 4, 2009 #13
    Re: At what distance from the conductor is the magnitude of the resulting magnetic fi

    i figured out my mistake thanx for your help

    the answer is 3.7286 cm
     
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