1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Use of phasor representation in physics

  1. Sep 7, 2013 #1
    Why do we use phasor representation in physics..For example,why we need maxwells equation in phasor form as well??
     
  2. jcsd
  3. Sep 7, 2013 #2

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

    Phasors are good for waves of constant frequency ... hence electrical engineers use them for AC circuits, and they use them a lot.

    So you will probably only use phasors while studying AC circuits; they are useful only for linear systems.
     
  4. Sep 9, 2013 #3
    ok ,thank you for the reply...what made me ask this question is-i saw maxwells eqautions(electromagnetic) written in phasor form from dpoint form by just substituting d/dt with jw..So what my questin is ,what is the implication of removing that time factor from that equation??
     
  5. Sep 9, 2013 #4

    UltrafastPED

    User Avatar
    Science Advisor
    Gold Member

    They were working in frequency space ... same place you go with the Laplace transform, or its cousin the Fourier transform.

    In this case they assumed that the electromagnetic field was a harmonic wave - and plugged this into Maxwell's equations - leaving you with the "Phasor form of Maxwell's equations".

    Here is a lecture which includes the derivation: http://ivp.ee.cuhk.edu.hk/~ele3310/data/ELE3310_Tutorial_10.pdf
     
  6. Sep 9, 2013 #5

    jasonRF

    User Avatar
    Science Advisor
    Gold Member

    Another reason is that properties of media are "easy". For example, for electric field:
    [tex]
    \mathbf{D} = \epsilon_0 \mathbf{E} + \mathbf{P}
    [/tex]
    but it is only for a single frequency that
    [tex]
    \mathbf{P}(\omega) = \epsilon_0 \chi_e (\omega) \mathbf{E}(\omega).
    [/tex]
    In the time domain we in general have a convolution,
    [tex]
    \mathbf{P}(t) = \epsilon_0 \int^t d\tau \, \, \, \chi_e (\tau) \mathbf{E}(t-\tau).
    [/tex]

    jason
     
  7. Sep 13, 2013 #6

    Claude Bile

    User Avatar
    Science Advisor

    You can assume a time dependence of exp(jwt) without losing generality due to the principle of superposition. For incident fields with multiple frequency components, you can solve Maxwell's equations for each frequency component, then sum the solutions at the end as required.

    Claude.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Use of phasor representation in physics
Loading...