What is the impedance if the voltage of the line is 115 volts?
Impedance, however, does not equal the sum of resistance and reactance.
The impedance of its secondary will be a quarter of this or 3,000 ohms.
The impedance of the coil I is changed by moving its adjustable core.
Impedance depends chiefly upon the frequency of alternation.
An important factor in the design of impedance coils is the grade of iron used in the magnetic circuit.
The usual diagrammatic symbol for an impedance coil is shown in Fig. 106.
The symbol of Fig. 104 is a good one for the toroidal type of impedance coil.
These four impedance coils are wound on separate cores and do not have any inductive relation whatsoever with each other.
In order to further increase the impedance, the cores are made long and heavy.