As an electric motor’s rotor turns in close proximity to the motor windings, a bucking voltage or back electromotive force (EMF) is generated. The back EMF (BEMF) generated across the start winding is greater than what is generated across the run winding. This phenomenon happens because the start winding usually has longer wire, smaller diameter wire, or more turns of wire, thus has a greater inductive reactance than the run winding. Because of this, potential relays are sometimes referred to as voltage relays since they rely on the BEMF or voltage that is generated by the motor for their operation.