ECE201_Lecture36

ECE201_Lecture36 - ECE201 Linear Circuit Analysis I Lecture...

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1 ECE201 Linear Circuit Analysis I Lecture 36 Topic: Instantaneous and Average Power 1. Instantaneous power in the sinusoidal steady-state (1) Definition: (2) A general case: v(t) = V m cos( ω t + θ v ) (“m” is short for maximum in V m ) i(t) = I m cos( ω t + θ i ) then p(t)= v(t) i(t) = V m cos ω t + θ v ( ) × I m ω t + θ i ( ) ( ) ( ) 11 cos cos cos cos 22 α β= α−β + ( ) ( ) mm vi VI cos cos 2 t constant term sinusoidal term at twice the frequency 2 ω = θ −θ + ω +θ +θ   (3) Note that if the impedance of the two-terminal device is Z(j ω )=|Z| ∠θ Z , then θ v − θ i = θ z this follows from ( ) V Zj I ω= device + v(t) i(t) > 0 absorbed p(t) = v(t) · i(t) < 0 delivered (passive sign convention)
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ECE201_Lecture36 - ECE201 Linear Circuit Analysis I Lecture...

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