State maximum power transfer theorem
The Maximum Power Transfer Theorem states:
Maximum power is delivered to a load when the load resistance is equal to the internal (source) resistance of the network as seen from the load terminals.
Mathematical condition
-
For DC circuits:
RL=RthR_L = R_{th}RL?=Rth? -
For AC circuits:
ZL=Zth∗Z_L = Z_{th}^*ZL?=Zth∗?(i.e., load impedance is the complex conjugate of the source/Thevenin impedance)
Key idea
When the load matches the source, power transfer is optimized—even though efficiency is only 50% at this point.
