. Practical wireless telegraphy; a complete text book for students of radio communication . ve so many ohms capacity reactance. In caseinductance reactance predominates, the opposite statement applies. We see from all thisthat a much greater current can be made to flow through the circuit from the alternatorby the use of a condenser and a coil than if but one of these were used. Reviewing the foregoing, it is clear that the reactance of a given coil for frequenciesin excess of 100,000 cycles per second (as compared to lower frequencies) may attain arather large value. It is therefore nec-essar
. Practical wireless telegraphy; a complete text book for students of radio communication . ve so many ohms capacity reactance. In caseinductance reactance predominates, the opposite statement applies. We see from all thisthat a much greater current can be made to flow through the circuit from the alternatorby the use of a condenser and a coil than if but one of these were used. Reviewing the foregoing, it is clear that the reactance of a given coil for frequenciesin excess of 100,000 cycles per second (as compared to lower frequencies) may attain arather large value. It is therefore nec-essary in such circuits to insert a cer-tain amount of concentrated capacity tobuild up the current. In the radio-frequency circuits of wireless telegraphapparatus, current flows at frequenciesbetween 20,000 and 1,000,000 cycles persecond and if this current is to be trans-ferred by magnetic induction from onecircuit to another, the second circuitmust contain a certain amount of in-ductance and capacity of such valuesthat inductance reactance and capacityreactance neutralize one another. The. 60 Fig. 45—Sliowing How Resonance Is Obtained in Alter-nating Current Circuits. second circuit is then said to be resonant to the impressed frequency and the flow of current isgoverned solely by its resistance. Straight wires possess both capacity and inductance, which are said to be dis-tributed rather than concentrated as in the case of a condenser or a coil of laws of electrical resonance, in general, apply to such circuits as well as thosehaving concentrated capacity and inductance. 47. Lag and Lead of Alternating Current.—A certain phenomenon, in-volved in the flow of alternating current throughout a given circuit, is termedphase displacement. Given a circuit in which inductance reactance predominates,it is found that when a given alternating electromotive force is applied thereto, thepressure and current do not reach their maximum values simultaneously. Thecurrent l
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