Question on power formula

Discussion in 'Homework Help' started by wind_blast942, Oct 21, 2011.

  1. wind_blast942

    Thread Starter New Member

    Sep 7, 2010
    Hi all

    I have a question regarding the power formula.

    For power in terms of voltage, we have: 1/2 * |V|^2 * Re{1 / Z*}, where Z* is the complex conjugate of Z.

    However according to the power formula I learnt last time using RMS value,
    P = V (rms)^2 / R
    = (V (peak)/sqrt(2))^2 / R
    = 1/2 * V(peak) ^ 2 / R,

    however the R term here is not a complex conjugate; but this equation is applicable for AC circuits, where R can have imaginary parts.

    The question i have is whether the 2 formulas are similar and referring to the same thing, and if so, why does it look different?