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Need some diffential equation help

  1. Jan 24, 2006 #1
    ok, i am having a bit of trouble with this equation.
    The question in the book is i need to find the maximum current(I) in an LR circuit, with L=10 Henry, and the Resistor of 1 ohm, and the time that it occurs. It also states that the emf E is given by E(t) = 5exp(-.05t) with the initial condition that the current (I) at time t=0 is 0
    ok , i know that L(dI/dt) + IR = E, and i simplified it down to 10I' + (1/10)I = 5exp(-.05t). i also know that this equation is not separable, so i need to find an integrating factor, but unfortunately, my teacher was very vague about how to find and use the integrating factor.
    I know that the integrating factor comes from the first order general equation x'(t) = a(t)x(t)+f(t), and also i know that the integrating factor u is Exp(integral(a(t)dt)). so in this case, am i right to say that the integrating factor is exp(-t)?
    finally, i am totally lost when it comes to actually using the integrating factor. any help would be greatly appreciated
    never mind, i figured it out!
    Last edited: Jan 25, 2006
  2. jcsd
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