ART. 92 - Comparison of Methods for the Determination of Resistances in Absolute Measure  pp. 134-150

Comparison of Methods for the Determination of Resistances in Absolute Measure

By John William Strutt

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At the present time, and in view of the projected conference at Paris, the subject of the present paper is engaging a large share of attention; and Prof. G. Wiedemann has published an interesting discussion of some of the methods that have been employed. I have thought it might be of service if I also were to place upon record the views that I have been led to entertain, and which are the result of a good deal of experience.

Resistance being of the dimensions of velocity, its absolute measurement involves the absolute measurement of a length and of a time. The latter is usually the time of a vibration of a suspended magnet, and it can be determined without much difficulty. In the b.a. method it is the time of rotation of the revolving coil, and it can be obtained with all desirable accuracy. In this respect there is not much to choose between one method and another; but when we come to consider the manner in which the linear measurement enters, important differences reveal themselves. These will be discussed in detail presently; but for the moment it will be sufficient to say that the presumption is in favour of any method which requires only a single linear measurement. It is true that this question cannot be decided without regard to the subject of the measurement; but, with scarcely an exception, it is necessary to know the mean radius of a coil of several layers of insulated wire.

Scientific Papers Volume 1

John William Strutt Baron Rayleigh

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