Fig. 1,266.—Inductance test, illustrating the self-induction of a coil which is gradually increased by moving an iron wire core inch by inch into the coil. The current is kept constant with the adjustable resistance throughout the test and readings taken, first without the iron core, and again when the core is put in the coil and moved to the 1, 2, 3, 4, etc., inch marks. By plotting the voltmeter readings and the position of the iron core on section paper, a curve is obtained showing graphically the effect of the self-induction. A curve of this kind is shown in fig. 1,302.
Ques. Define inductance.
Ans. It is the total magnetic flux threading the circuit per unit current which flows in the circuit, and which produces the flux.
In this it must be understood that if any portion of the flux thread the circuit more than once, this portion must be added in as many times as it makes linkage.
Inductance, or the coefficient of self-induction is the capacity which an electric circuit has of producing induction within itself.
Inductance is considered as the ratio between the total induction through a circuit to the current producing it.
Ques. What is the unit of inductance?
Ans. The henry.
Ques. Define the henry.