Induction-Coil Potentials Page 586

\(i_0 = 1·25\) amp. and without the external inductance the maximum spark-length (\(C_1 = ·05\) mfd.) was 2·81 cm.; with the external inductance and the same primary current the longest spark was 5·36 cm., and the most effective capacity for this case was ·2 mfd.

The experimental results therefore agree with the theory in indicating that the most effective adjustment of the system (from the point of view of spark-length) is that in which \(n_2 = 3n_1\), and \(U\) is at its maximum. It is probable that most induction-coils have coefficients of coupling which are greater than ·8, and in such cases the method here described may be used for making the coil give a longer spark with a given primary current, or a given spark-length with a smaller current.

The actual values of the secondary potential can only be calculated when the effective resistances are determined for each case, but it is not probable that these latter results would be greatly modified by their introduction. On the whole the evidence tends to show that the theory described in this and the two former papers is sufficient for the calculation of the secondary potential of an induction-coil and the most effective value of the primary capacity.

Bangor, February 1914.