The measurement of the inductance of iron-cored chokes carrying direct current
E O Willoughby · Proceedings of the Physical Society · 1934
A method for measuring, by means of a reflecting dynamometer ammeter, the inductance of an iron-cored coil is described. The coil is connected in series with a capacity and the ammeter, and then the junction of the inductance and capacity and the junction of the fixed and moving coils are connected to an a.-c. supply. It is shown that for a constant applied voltage the deflection of the dynamometer ammeter is proportional to the square root of the reciprocal of the inductance. This is also true when a direct current is superimposed on the alternating current flowing through the inductance. Advantages of the method are the simplicity of the measuring instruments and of the observations taken, the small value of the alternating current used (which corresponds to the alternating current in certain applications of chokes in wireless sets), and the independence of the method within wide limits of the frequency and wave-form of the supply used.