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Which is the constant of differentiation?

  1. Oct 20, 2015 #1
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    When the textbook differentiated with respect to time, I see that the middle term is R(dI/dt). Why can't it be I(dR/dt)? When I differentiate, how do I know which letter to differentiate?
    3. The attempt at a solution
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    1. The problem statement, all variables and given/known data
     
    Last edited by a moderator: Oct 20, 2015
  2. jcsd
  3. Oct 20, 2015 #2

    LCKurtz

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    L, R, and C are constants. You are differentiating with respect to time and the constants don't vary.
     
  4. Oct 20, 2015 #3

    SammyS

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    Why did you ignore the template? You even went through the trouble to change the font color.

    To answer your question:

    R is a constant just like L and C. You had no objection to treating them as constants.
     
  5. Oct 20, 2015 #4
    I see... If I look at the original equation (1.2) has ##\frac{dI}{dt}## and that tells me that I is not a consant?
     
  6. Oct 20, 2015 #5

    SammyS

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    Actually, it helps to understand something of the physics behind this problem.

    V is voltage or emf. I is current.
     
  7. Oct 20, 2015 #6
    The example was on differential equations in general, so the textbook didn't give me background information on the physics.
     
  8. Oct 21, 2015 #7

    NascentOxygen

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    You could use the product rule, differentiating the product RI w.r.t. time. What result would you get?
     
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