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Vector Calculus (Maxwell's equations and the Poynting Vector) Watch

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    Q5 here: http://www.damtp.cam.ac.uk/user/examples/A5d.pdf

    Really have no idea where to go with this. I have no idea where c^2 could possibly come from and I tried finding dpi/dt and got to this:

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    And frankly I think all of that is absolute rubbish.

    Any help would be appreciated.

    Thanks
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    I think you've done some unnecessary steps - it should become a bit clearer if you use that c^2 = \frac1{\mu_0 \epsilon_0}, and I would find dT/dxi too (you then see some structural similarity).
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    (Original post by Smaug123)
    I think you've done some unnecessary steps - it should become a bit clearer if you use that c^2 = \frac1{\mu_0 \epsilon_0}, and I would find dT/dxi too (you then see some structural similarity).
    Right, okay. I'm not too sure how to differentiate the first part of Tij (the part with delta ij). It's just a scalar multiple of the identity matrix right? I'm not too sure what to do with that.
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    (Original post by Intriguing Alias)
    Right, okay. I'm not too sure how to differentiate the first part of Tij (the part with delta ij). It's just a scalar multiple of the identity matrix right? I'm not too sure what to do with that.
    You can treat the delta function with differentials just as normal: \delta_{ij} \frac{dx_i}{dy_j} = \frac{dx_i}{dy_i}.
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    (Original post by Smaug123)
    You can treat the delta function with differentials just as normal: \delta_{ij} \frac{dx_i}{dy_j} = \frac{dx_i}{dy_i}.
    I managed it now, thanks for the help.
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    (Original post by Intriguing Alias)
    I managed it now, thanks for the help.
    No problem I should really do that sheet - my supervisor gives us different ones, the questions are broadly the same, but I see that the official sheets have much more Maxwell in them, so if that's a hint as to what will come up in the exam…
 
 
 
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