Supplementary note to the "Study of the High-Frequency Resistance of Single Layer Coils"

Since the publication of the above paper in the December, 1930, number of the Proceedings of the IRE, the attention of the authors has been called to two articles on the alternating-current resistance of solenoidal coils, by S. Butterworth, which they regret to state were overlooked in the preparation of the original paper. In the first of these articles (Phys. Rev., 11, 752-755; June, 1924) Butterworth has explained the disagreement of results, calculated by a formula derived by him in 1921, and the experimental results of Hickman (US Bureau of Standards Scientific Paper No. 472) as being due to a misinterpretation by the latter of the scope of this formula. The measurements of Hickman were carried out with long coils, while the constants in the formula cited apply only to coils whose length is less than their diameter. Butterworth shows that, properly extended, his formula correctly represents Hickman's experimental values of the resistance ratio. In the second of these articles Butterworth gives the derivation of this extended expression, formula together with that of two other formulas. In conclusion, the general agreement of the above-named paper's measured values and the values of resistance ratio computed by Butterworth's formulas may be regarded as satisfactory in all cases where the assumptions of the formulas are fulfilled. For a more rigid comparison, measurements are necessary with coils of more open winding and with greater attention paid to obtaining uniformity of spacing over the length of the coil.