doubt

Discussion in 'Math' started by shiva bharadwaj, Sep 29, 2008.

  1. shiva bharadwaj

    Thread Starter Member

    Sep 29, 2008
    19
    0
    hi guys
    while solving problems in laplace transforms we usually substitute s=jω but actually s=σ+jω why are we neglecting σ here?
    what is its significance?
     
  2. darenw5

    Active Member

    Feb 2, 2008
    45
    0
    A particular example might help with getting a clear crisp answer, but generally, that sigma helps make an the integral converge. The result doesn't depend on the value of sigma; like limits in beginning calculus, you can't just throw in zero, but approach it carefully. I hope that makes sense...
     
  3. Ratch

    New Member

    Mar 20, 2007
    1,068
    3
    shiva bharadwaj,

    Notice how I inserted capitalization and punctuation in your question. Sigma is not being neglected, it is just zero for sinusoidal waveforms. The substitution is NOT made for nonsinusoidal functions. You did not mention that. Any good book on Laplace transforms will show you why substitution of jw in a Laplace expression gives the phasor representation of that function.

    Ratch
     
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