Polarity (mutual inductance)

The polarity of a device with mutual inductance designates the relative instantaneous current directions of such device's winding leads.

A dot marking convention, or alphanumeric marking convention, or both, can be used to denote the same relative instantaneous polarity of two mutually inductive components such as between transformer windings. These markings may be found on transformer cases beside terminals, winding leads, nameplates, schematic and wiring diagrams.