Need help understanding voltage

Discussion in 'Homework Help' started by kyro1214, Oct 4, 2009.

  1. kyro1214

    Thread Starter New Member

    Oct 4, 2009
    Assume the charge at the upper terminal is zero at the instant the current is passing through its maximum value. find the expression for q(t).
    i = 24cos4000t A

    im not sure if i taken the correct integral of it. i got q(t) = (24cos4000t)1/2t^2

    also for the same question but when i=0 when t<0 and i=20e^-5000tA when t> or equal to 0.
  2. steinar96

    Active Member

    Apr 18, 2009
    Hmm, the integral of cos is sin. So the final function should have a sin in it. And also when you integrate cos(kt) where k is a constant you get sin(kt) divided by the stuff inside the cos function differentiated. That is

    sin(kt) / k.

    Try integrating again with this in mind.