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Homework Help: Magnetism, Credit-Card magnetic strips

  1. Dec 12, 2014 #1


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    1. The problem statement, all variables and given/known data
    Experiments carried out on the television show Mythbusters determined that a magnetic field of 1000 gauss is needed to corrupt the information on a credit card's magnetic strip. (They also busted the myth that a credit card can be demagnetized by an electric eel or an eelskin wallet.) Suppose a long, straight wire carries a current of 2.5 A. How close can a credit card be held to this wire without damaging its magnetic strip?

    I'm not quite sure how to go about this problem, could anyone please explain it?

    2. Relevant equations
    Magnetic field of a solenoid: upload_2014-12-12_16-59-23.png
    Where n=N/L

    3. The attempt at a solution
    Answer: 5.0µm
  2. jcsd
  3. Dec 12, 2014 #2


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    Science Advisor
    Homework Helper
    2017 Award

    Hi Nn,

    Your relevant equation isn't for a simple straight wire. Look e.g. here

    Oh, and: next time use the template as it's intended (I.e. show some work under 3, not the answer from the back of the book) :)
  4. Dec 12, 2014 #3


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    Thanks for pointing that out! I didn't know how to calculate it, so I put the correct answer there for those who could help
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