High-frequency resistance of inductance coils
GREGORY A. BREIT · Scientific Papers of the Bureau of Standards · 1922
The definition of tlie resistance of a coil is simple for direct current and may be given directly in terms of Ohm 's Law.Similarly, the computation of the resistance of a coil made of a wire of known length, cross section, and material is quite easy for direct current.The same problem becomes difficult if an alternating current of high fre- quency is used instead of a direct current.It is shown in this paper that a different definition of resistance must be given ; that the value of the resistance thus defined depends upon the point in the coil with respect to which the resistance is defined ; and it is shown how the resistance-variation method, described in Btu-eau of Standards Circular 74, may be employed to measure the resistance thus defined.A formula is derived for the value of the current at any point of the coil when the emf induced in any portion of the coil is known.This formula is compared with the experimental results obtained on coil aerials.This formula presupposes the knowledge of the resistance measiured by the resistance -variation method with respect to all points on the coil.In order to know this resistance, it is sufficient to know the resistance as measured with respect to one point and also to know the distribution of current in the coil.The value of the resistance with respect to one point of the coil is worked out and the result is verified experimentally.