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Homework Help: Time constant in RC AC and RL AC Circuits?

  1. Oct 25, 2012 #1
    1. The problem statement, all variables and given/known data
    I know that in a RC DC circuit the time constant is R*C. But what about a RC AC circuit, is it the same time constant?

    Same goes with RL AC circuit, is the time constant R/L?

  2. jcsd
  3. Oct 26, 2012 #2


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    Staff: Mentor

    For AC (sinusoidal) circuits we're more often interested in the "steady-state" conditions that exist for continuously applied AC signals. In this scenario the time constants "##\tau##" don't have quite the same import for signal shape that they do for transient analysis since all the steady-state circuit responses are sinusoidal too.

    For AC circuits the time constant expressions are more useful for determining how a given circuit will behave at different frequencies, and ##1/\tau## represents an important "landmark" in response-versus-frequency analyses.
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