| Imax × 2 / π | Imax | ||||
| condenser pressure | = | = | (6) | ||
| 4fC | 2πfC |
This last equation (6) represents the condenser pressure due to capacity at the point of maximum value, which pressure is opposed to the impressed pressure, that is, it is the maximum reverse pressure due to capacity.
Now, since by Ohm's law
| E | ||||
| I | = | = | I × R | |
| R |
and as
| Imax | 1 | |||
| = | Imax | × | ||
| 2πfC | 2πfC |
it follows that 1 / (2πfC) is the ohmic value of capacity, that is it expresses the resistance equivalent of capacity; using the symbol Xc for capacity reactance
EXAMPLE.—What is the resistance equivalent of a 50 microfarad condenser to an alternating current having a frequency of 100?
Substituting the given values in the expression for ohmic value
| 1 | 1 | 1 | ||||||
| Xc | = | = | = | = | 31.8 ohms. | |||
| 2πfC | 2 × 3.1416 × 100 × .000050 | .031416 |