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!

Question about variational derivative

  1. Jun 29, 2012 #1
    I have a question as to what notation should I use for the following derivation ( I have no background on calculus of variation ):

    In linear media , the stored energy in a given volume is given by

    [itex]W_{mag}=\int_{V}\frac{1}{2}H.Bdv[/itex]

    Now intuitively

    1) [itex]H=\frac{d W_{mag}}{dv d B}[/itex]


    But this is not the way they write it, instead one of the following notations are used:


    2) [itex]H=\frac{\partial W_{mag}}{\partial B}[/itex]
    3) [itex]H=\frac{\delta W_{mag}}{\delta B}[/itex] ( dv is missing)

    What is the right notation for equation 1 ?


    Thanks.

    Edit: In 1) it is assumed that B inside the infinitesimal volume (dv) changes to B+dB while outside dv it remained constant.
     
    Last edited: Jun 29, 2012
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted