2. The capacity pressure, or pressure necessary to overcome the condenser pressure,
The capacity pressure is 90 degrees behind the current.
Fig. 1,329.—Graphical method of obtaining the impressed pressure in circuits containing resistance and capacity, having given the ohmic drop and reactance drop due to capacity. With any convenient scale, lay off AB = ohmic drop, and at right angles to AB draw BC = reactance drop (using the same scale). Join AC, whose length (measured with the same scale) will give the impressed pressure. The mathematical expressions for the three quantities are given inside the triangle, and explained in the text.
Problems involving resistance and capacity are solved similarly to those including resistance and inductance.
The Active Pressure or "Ohmic Drop."—This, as before explained is represented, in fig. 1,329, by a line AB, which in magnitude equals, by Ohm's law, the product of the resistance multiplied by the current, that is,
Ea = RoIv (1)
Fig. 1,330.—Diagram of circuit containing a resistance of 30 ohms and capacity of 125 microfarads. The calculation for impressed pressure, ohmic drop, and reactance drop for a current of 8 amperes at frequency 60 is given in the example on page [1,089], the diagram for impressed pressure being given in fig. 1,331.