Conductance is the reciprocal of resistance. It measures how easily current flows. High conductance = low resistance = easy current flow. The unit siemens (S) is named after Ernst Werner von Siemens. In circuit analysis, conductance simplifies calculations for parallel circuits since parallel conductances simply add.
⚠Conductance rules are the dual of resistance rules. Parallel resistance: reciprocals add. Parallel conductance: values directly add. Series resistance: values add. Series conductance: reciprocals add. Always check if you are working with R or G!
Understanding Conductance
Conductance is particularly useful in parallel circuit analysis because parallel conductances add directly (Gt = G1 + G2 + ...). This avoids the reciprocal calculations needed for parallel resistance. Conductance is also used in semiconductor physics (channel conductance), electrolytic solutions, and power system analysis (admittance = conductance + j susceptance).
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