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Can't solve it - I think some data is missing for this to be solvable

  1. Jan 18, 2007 #1

    I recently started learning about magnetic fields and magnetic induction.
    I tried to solve the following two problems, but I got stuck. Could you please help?

    Current of 15 A is running through the wire loop and magnetic flux throught the wire loop is 3 Wb. What is inductivity L of a wire-loop? Here we obviously can't use formula for inductivity of a coil, so ... I don't know how to go at it.

    I = 15 A
    FL[ux] ... 3 Wb


    Current of 20 A creates inside a coil a magnetic flux of 10 Wb. What is the induced voltage U of a coil, if current decreases by 1.2 A each second? I tried to solve it but clearly there are some variables missing - like length of a coil or area of a wire-loop.

    I = 20 A
    FL[ux] = 10 Wb
    dI = 1.2 A
    dt = 1 s

    U = ?

    Like I said, length of a wire is missing for this to be solvable.

    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jan 18, 2007 #2


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    Why can't you use the formula for the inductance of a coil?

    Note that [itex]Li = N\phi_{B}[/itex]
  4. Jan 18, 2007 #3
    Uh, I got it now.

    I got it now. I didn't notice that problem already stated how many turns coil has.

    thank you
    Last edited: Jan 18, 2007
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