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Power consumption in LCR circuit

  1. Feb 19, 2016 #1
    If we have a variable frequency AC supply in LCR circuit and when the frequency equals natural frequency the impedence is equal to resistance and the power consumption is purely that of resistive load circuit.
    Is this true even for other frequencies i.e. do reactance participates in power consumption or not.
  2. jcsd
  3. Feb 19, 2016 #2


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    Reactances do not consume power. They store the energy and release it back to the source in a cycle. Power is consumed only by the resistive loads. In case of resonance, power factor of the circuit is unity, meaning the reactive power is 0. So, whatever power is input, all of it is consumed in the resistor.
  4. Feb 19, 2016 #3


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    It's worth while pointing out that the reactances in a circuit can affect the amount of power dissipated by the resistive elements. The LC combination can match or mismatch the load R (Edit: transform it) and the source, despite not dissipating any power themselves. For instance, the low power dissipated by a high resistance from a low voltage AC supply can be increased as much as you like by LC matching. The only limit is when you hit the Maximum Power Theorem condition, where the source resistance is the same as the transformed load resistance.
    Last edited: Feb 19, 2016
  5. Feb 19, 2016 #4
    Worth mentioning that varying the frequency will impact the impedance which varies the current passing through R. Therefore, the reactances play a role in the power absorbed by R, although L & C do not consume power.
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