In circuit analysis, the dot convention
is a convention
used to denote the voltage polarity
of the mutual inductance
of two components. Two good ways to think about this convention:
- The current going into one dot (either dot) "tries" to come out the other dot. "Into" meaning from the dot toward the inductor, and conversely "out" meaning from the inductor toward the dot.
- ''Current going into a dotted terminal of the inductor induces a positive voltage at the other dot. Conversely, current leaving a dotted terminal inductes a negative voltage at the other dot.
Voltages might be a less confusing way of looking at this concept, but might be harder to remember. As shown below, the dot convention distinguishes between two cases, where the polarities of the top node are the same, and when they are different. There are two ways to write each case, and the equivalent ways of writing them are shown.