# Question on power formula

#### wind_blast942

Joined Sep 7, 2010
22
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?

Thanks.