Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help with home work question, RL circuit

  1. Feb 20, 2009 #1
    vf= 4(u(t)-u(t-1.8))v

    I have to find i(t), for the attached circuit. I already evaluated it for t<0. But i a having problems in the rage 0<t<1.8.

    I am at the point where i have to find the forced response, so o let t tend to infinity
    (t->infinity). And so the Inductor acts like a short circuit, the problem i have is find the current that passes where the inductor short circuits, I get confused by the controlled current sources.

    I so far used kirchoff voltage law to find three equations, but i am not sure i am correct, nor what to do with the dependent current source that finds itself in an equation.
    Thanks for helping...


    Attached Files:

  2. jcsd
  3. Feb 20, 2009 #2
    is there any simple way of calculating i1 in the circuit, that would make things a lot easier.
  4. Feb 20, 2009 #3
    Ok, i am thinking i1=i-(4v/5ohms). Note i got the 4 volts( which is supplied by the independent voltage source) from the scalar function vf, when evaluated in the range 0<t<1.8.
  5. Feb 21, 2009 #4
    I've never seen some of the circuit elements in your drawing. Who's reinventing electronics and why?

    I think if you want any help, you're going to need to decode that stuff.
  6. Feb 21, 2009 #5
    Sorry about that. I didn't use a circuit schematic program to draw the circuit. I actually labelled them. I was hoping that would be sufficient. I solved the question yesterday one hour before the class. I will post the solution and a proper diagram shortly.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook