Dot Convention - Sinusoidal AC

Sinusoidal AC

For sinusoidal AC such as the mains, the convention can be thought of in either of the following ways:

1. 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.
2. A current going into a dotted terminal of the inductor induces a voltage which is in phase at the other dot.