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

Homework Help: Damping in Electrical Circuits

  1. Apr 11, 2005 #1
    Could someone please give me a QUALITATIVE description of:

    -critical damping
    -over damping
    -under damping

    So I can understand the physics behind the oscillatios in a circuit. I know the mathematical explanations (ie. over damping is when the characteristic polynomial solutions are both negative real numbers etc).

    Thanks :tongue:
  2. jcsd
  3. Apr 11, 2005 #2


    User Avatar
    Science Advisor

    It might be clearer to think of this in terms of a "shock absorber" system in a car: a spring with a damping force.

    "under damped" means you - bounce, bounce, bounce with each bounce less than the one before. If you graph the motion (or the current in a circuit) you see a succession of peaks and valleys with the height between peak and valley getting smaller. If you put an ammeter into an "under damped" circuit, you see the needle swinging back and forth between positive and negative- a little less on each side with each swing, until it settles at 0.

    "over damped" is no bouncing at all. There is a smooth return from the height to 0. If you graph that, you see a smooth curve dropping to 0 but not going below 0. If you put an ammeter in an over damped circuit, you see the needle swinging steadily down to 0.

    "critically damped" looks exactly like "over damping"- there is no swing below and then back above 0. The only difference between "over damped" and "critically damped" is that if you reduce the damping at all, you get "under damped".
  4. Apr 11, 2005 #3
    ok thanks that really helps. So is basically critical damping sort of mid-way between under damped and over damped in the sense that it provides just enough damping to reduce most of the amplitude of oscillation, but the oscillation still actually continues?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook