The Theory and Practice of Absolute Measurements in Electricity and Magnetism Volume 2
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1893 edition. Excerpt: ...from the known data of the coil and thus R is found. In no practical case can nM be large, and therefore K must be Lord Ray small, and a difficulty arises on this account in the carrying out lelK" auii of the method. This was overcome in Lord Rayleigh and . "?, Mrs. Sidgwick's experiments by arranging that the main current j1.' S should flow along AC (Fig. 131), through a resistance a small mens. Fig. 131. compared with the resistance e between A and B, while at the two points B and C, including a resistance 6 also small compared with a, the terminals connected with the revolving disk were applied. Thus b was the resistance which was evaluated by the experiment. The connections at A, B, C were made by means of mercury cups. The main current being y, and no current flowing in the circuit applied at BC, the current through A B C is yaja--b--c). Hence the difference of potential between B and C was yabj(a + b + c). This was therefore the electromotive force generated by the motion of the disk. It will be convenient to regard it as the difference of potential produced by the current y between the ends of a conductor of resistance abja + b-f-e). Arrango-The pair of coils used by Glazcbrook in his determination of nient of the ohm (see abovo, p. 543) were employed, and were at first Apjiara-placed close together with the disk between them, so as to give a maximum inductive effect The axle was mounted vertically in the frame already used for the spinning coil determinations. so that the arrangements then used for driving and measuring the speed were available also in the present case. The diameter of the disk was about-6 of that of the coil. This size was chosen as on the one hand it was not desirable to have any part of the...
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- 13 Sep 2013
- Illustrations, black and white