dot-polarity-sum-three-row-scan - Electronic Circuits XV: Transformers and Coupled Inductors Step by Step

Dot polarity rows separate cancellation, addition, and difference. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Dot polarity chooses addition or subtraction

Every polarity row cites two distinct winding-voltage sources before computing output.

V_{\text{out}}=V_a\pm V_b

Three polarity rows separate cancel, add, and difference

Equal opposing windings cancel, equal aiding windings add, and unequal opposing windings leave a difference.

\begin{array}{c|c|c|c}V_a&V_b&\text{mode}&V_{\text{out}}\\4\ \text{V}&4\ \text{V}&\text{opposing}&0\ \text{V}\\4\ \text{V}&4\ \text{V}&\text{aiding}&8\ \text{V}\\6\ \text{V}&4\ \text{V}&\text{opposing}&2\ \text{V}\\\end{array}

The final polarity row subtracts the cited winding voltages

The displayed difference is not a free label; it cites the two winding rows and the opposing sign rule.

6\ \text{V}+\left(-4\ \text{V}\right)=2\ \text{V}