Phase

Phase refers to the temporal relationship of two (or more) sinusoidal alternating current signals of the same frequency. If two signals reach their maximum positive voltage at the same point in time, they are said to be 'in phase'. The relationship between two such signals is measured in 'degrees': in phase signals (above) are 0 degrees apart; if a second signal reaches its maximum negative voltage at the same time as another reaches its maximum positive voltage, they are said to be 180 degrees apart, or 'maximally out of phase'.