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RLC second order circuits

  1. Mar 16, 2019 #1
    1. The problem statement, all variables and given/known data
    2qcgodf.png
    2. Relevant equations
    V(t) = V(∞)+( V(0+) - V(∞) )e^-t/τ

    3. The attempt at a solution

    11tml2e.png
    Hello again! I've already solved the problem depicted in the picture above and below are the following unknowns that I managed to solved:
    205fdi0.png
    These results checked out with the answers supplied by the book. By I could not make sense out of these results. For example how come that at t=0+ the rate of change of the voltage across the 2-ohm resistor is dVr(0+)/dt = 2/3 v/s, when in fact the expression for the voltage across it is Vr(t)=4 V ----> this is a constant value how come it has a rate of change of some sort? Same confusion I have with the rate of change of voltage across the capacitor because Vc(t)=-20v.

    Please enlighten me with this matter. Thank you!
     

    Attached Files:

  2. jcsd
  3. Mar 16, 2019 #2

    rude man

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    Homework Helper
    Gold Member

    What reasoning led you to conclude constant voltages for the 2 ohm and C? When the switch is closed for the 3A supply, everything starts to move - all voltages, all currents!
     
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