Power Factor.—When the current falls out of step with the pressure, as on inductive loads, the power factor becomes less than unity, and the effect is to increase the current required for a given load. Accordingly, this must be considered in calculating the size of the wires. As has been explained, the current flowing in an alternating current circuit, as measured by an ammeter, can be resolved into two components, representing respectively the active component and the wattless component or idle current. These are graphically represented by the two legs of a right triangle, of which the hypothenuse represents the current measured by the ammeter.
This apparent current, as is evident from the triangle, exceeds the active current and lags behind the pressure by an amount represented by the angle ϕ between the hypothenuse and leg representing the energy current as shown in [fig. 2,694].
Fig. 2,694.—Diagram showing that the apparent current is more than the active current, the excess depending upon the angle of phase difference.
Fig. 2,695.—Diagram showing components of impedance volts. Compare this diagram with [figs. 2,689] and [2,671], and note that the term "reactance" is the difference between the inductance drop and the capacity drop if the circuit contain capacity, for instance, if inductance drop be 10 volts and capacity drop be 7 volts then reactance 10-7 = 3 volts.
Ques. What determines the heating of the wires on alternating current circuits with inductive loads?
Ans. The apparent current, as represented by the hypothenuse of the triangle in [fig. 2,694].
Ques. How is the apparent current obtained?
Ans. Divide the true watts by the product of the power factor multiplied by the voltage.