Unformatted text preview: Founda'ons of Circuit Analysis: Passive Sign Conven'on DePiero EE 201 Learning Objec'ves • Apply the passive sign conven,on and compute power dissipated by circuit elements. Passive Sign Conven'on Ensures Conserva'on of Energy • Energy is Conserved When: – Total energy generated in a circuit equals the total energy dissipated. – Ignoring issue of energy storage for now… • Sign conven'on also helpful when assigning voltage polari'es in analysis problems. Sign Conven'on Determines Power Absorp'on/Delivery • In these cases, V>0 and I>0. • Passive devices (resistors) can only absorb power. I enters (+) • Ac've sources typically deliver power. I leaves (+) • Ac've sources can also absorb power. I enters (+) Power
Absorbed Power
Delivered Power
Absorbed Using Passive Sign Conven'on • 1) Works for an arbitrary direc'on for I ﬂow • 2) Label ac've elements (if unspeciﬁed). – Assume power is delivered. I ﬂows out (+) terminal. – If power is actually absorbed, then a V or I quan'ty will evaluate to a nega've value. • 3) Label passive elements. – Power always absorbed. I ﬂows in (+) terminal. • 4) Compute power dissipated as needed. – If posi've I ﬂows into (+) terminal
> Power absorbed. V>0 and I>0 in the above definitions! ...
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 Spring '08
 ARAKAKI
 power00, I00, passive00, sign00

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