. A text book of physics, for the use of students of science and engineering . C.[This corresponds to across-section of 1 squaremillimetre; but sincethe mass of the mercuryis much more easilymeasured with accuracythan the bore of thetube in which it is con-tained, the mass ratherthan the cross-section is defined. This definition of the ohm hasbeen rendered legal in this country. For practical use, several makers supply 1 ohm standards whichhave been standardised at the National Physical Laboratory. Oneform of standard ohm is shown in Fig. 814. The wire comprisingthe conductor is of platinum-si
. A text book of physics, for the use of students of science and engineering . C.[This corresponds to across-section of 1 squaremillimetre; but sincethe mass of the mercuryis much more easilymeasured with accuracythan the bore of thetube in which it is con-tained, the mass ratherthan the cross-section is defined. This definition of the ohm hasbeen rendered legal in this country. For practical use, several makers supply 1 ohm standards whichhave been standardised at the National Physical Laboratory. Oneform of standard ohm is shown in Fig. 814. The wire comprisingthe conductor is of platinum-silver and is inclosed in a brass ends of the wire are soldered to stout brass terminals whichare well amalgamated at the ends; when in use they resl inmercury cups. This makes certain that the resistance of thecontacts is very small. A hole running down the axis is provided,for the insertion of a thermometer. The whole is then inserted inan oil bath to ensure constancy of temperature. The certificateissued with the coil states the temperature at which it is FIG. 814.—Standard ohm coil. 880 MAGNETISM AND ELECTRICITY CHAP.
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishe, booksubjectphysics
