Hawkins Electrical Guide v. 05 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

The Capacity Pressure or "Reactance Drop."—This component of the impressed pressure, is, applying Ohm's law,

capacity pressure = capacity reactance × virtual current.

E_c = X_cI_v (2)

That is, the expression for capacity reactance X_c, that is, for the value of capacity in ohms is, as explained on page [1,048],

		1
Xc	=		(3)
		2πfC

Substituting this value of X_c in equation (2) and writing I for virtual current.

CAUTION—The reader should distinguish between the 1 (one) in (3) and the letter I in (4); both look alike.

Since the capacity pressure is 90° behind the current, it is represented in fig. 1,329, by a line BC, drawn downward, at right angles to AB, and of a length corresponding to the capacity pressure, that is, to the reactance drop.

The Impressed Pressure.—Having determined the ohmic and reactance drops and represented them in the diagram, fig. 1,329, by lines AB and BC respectively, a line AC joining A and C, will then be the resultant of the two component pressures, that is, it will represent the impressed pressure or total pressure applied to the circuit.

In the diagram it should be noted that the active pressure is called the ohmic drop, and the capacity pressure, the reactance drop.