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Homework Help: How to calculate the time over which flux changes

  1. Jul 3, 2013 #1
    1. if the magnetic flux linking all the turns of a 50 turn coil changes from 10 mWB to 20 mWB and induces an e.m.f. of 62.5 V in the coil, calculate the time over which the flux changes.

    i know the formula to calculate the flux which is

    E = -N change in flux / change in time.

    to calculate the change in time we just need to change E with change in time in the formula, but by doing this answer will be negative which is not possible as time can not be negative. how to get rid of this -ve. or is it ok if i dont use it at all.

    my answer is -0.008 Sec.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 3, 2013 #2

    rude man

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    Homework Helper
    Gold Member

    The 62.5V polarity was not defined with respect to coil geometry so your answer is correct when made positive.
  4. Jul 3, 2013 #3
    62.5 V is an absolute value of e.m.f
  5. Jul 4, 2013 #4
    thnx a lot guyz..... :D
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