induced emf

Discussion in 'Homework Help' started by lemon, Feb 8, 2010.

  1. lemon

    Thread Starter Member

    Jan 28, 2010
    125
    2
    a) The flux linking a coil of 2000 turns falls from 0.25 Wb to zero in 12.0s. What is the magnitude of the induced emf in the coil?

    b) The current in one coil of a pair of coils changes at 0.85A/s. Calculate the induced emf in the other coil if this coil is open circuit (no current flows) and the mutual inductance of the pair is 400mH.

    Equation: e=-L.di/dt
    Where di/dt is the rate of change gradient

    Answer:
    a) There is a decrease in flux of 0.25Wb in 12s.
    The induced emf opposes the current causing it.
    This is Lenz's law because it is a negative.

    -0.25/12s=-0.02V (2d.p.)
    Why do I have a feeling this is completely wrong :rolleyes:
    I think I may have used this equation wrongly. -L is the self inductance, right? So is that the flux change?

    Think I may need a lot of help here please :confused:
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    e=-dψ/dt=-N*dΦ/dt

    Have a go now.
     
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