= Maximum power transfer theorem
{title2=$R_L=R_s$}
{wiki}
A <Thévenin equivalent> voltage source $V_s$ with positive source resistance $R_s$ supplies load power $P_L=V_s^2R_L/(R_s+R_L)^2$ to a real resistive load. Differentiating gives its maximum at $R_L=R_s$. With reactive impedances and fixed source impedance, conjugate matching maximizes the average delivered power. Maximum delivered power is distinct from maximum efficiency; at a real resistive match half of the source's internally generated power is dissipated in $R_s$.
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