Source-Load Power-Split Three-Row Scan - Electronic Circuits II Step by Step

The source power splits into useful load power and source-resistor loss. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A source-load circuit spends power in two places

The source supplies power to the whole series path. The load receives part of it, and the source resistor dissipates the rest.

P_{\text{source}}=P_{\text{load}}+P_{\text{source resistor}}

Resistance split controls load power

Each row keeps the same source voltage and total resistance. The source power is 24 watts in every row; changing which resistor is the load changes where that power goes.

\begin{array}{c|c|c|c}R_s&R_L&P_L&P_r\\2\ \text{ohm}&4\ \text{ohm}&16\ \text{W}&8\ \text{W}\\4\ \text{ohm}&2\ \text{ohm}&8\ \text{W}&16\ \text{W}\\3\ \text{ohm}&3\ \text{ohm}&12\ \text{W}&12\ \text{W}\\\end{array}

The rendered row sends two thirds to the load

For the rendered row, source power is 24 watts and load power is 16 watts. The remaining power is the source-resistor loss.

16\ \text{W}+8\ \text{W}=24\ \text{W}