Induction-Coil Potentials Page 573

was used in order that the coupling of the two coils might be made as loose as possible. The oscillations were started by interrupting a current of 5 amperes in the primary, and the curves were photographed and measured in the usual way. The product \(L_1 C_1\) was calculated from the frequency, the ratio \(R_1/L_1\) from the logarithmic decrement, of the oscillation curve. The results of these measurements are given in Table IV. The corresponding quantities for the secondary circuit, \(L_2 C_2\) and \(R_2/L_2\), were determined from the period and logarithmic decrement of the oscillation produced in the secondary when a current of 5 amperes in the primary was interrupted. In this experiment the primary condenser was removed, and the secondary coil was connected only to the electrometer and the ball electrodes, so that the secondary capacity was the same as in the final experiments. The values so determined are given under Table IV. It should be observed that these values of \(L_1 C_1\) and \(L_2 C_2\) are maximum values, i.e. they correspond to a magnetizing current of about 5 amperes in the primary coil.

The effective resistances of the coils in the circumstances of the present experiments, as determined from the damping of the oscillations, are much greater than their resistances for steady currents. The influence of these resistances on the periods of oscillation is, however, neglected in all calculations in the present paper, i.e. both in the determination of \(L_1 C_1\) and \(L_2 C_2\) described above, and in the calculation of the frequencies of the coupled system given in the next section. That no great error is thereby introduced is shown by the close agreement between the observed and calculated periods in the final experiments.

Table IV.

\(1/L_2 C_2 = 8·974 · 10^6\) c.g.s.
\(R_2/L_2 = 215\) c.g.s.

Phil. Mag. S. 6. Vol. 27. No. 160. April 1914.