...circuit, multiplied by the effective current passing in that circuit, and multiplied again by the cosine of the angle by which the current lags behind the electromotive force in that circuit. The losses due to friction are divided between the circuits; but each circuit has...

...motor principles: V. The effectiveness of armature reaction in weakening the field is proportional to the sine of the angle by which the current lags behind the impressed pressure. If a motor be without load or friction, its armature will revolve synchronously...