Practical Electricity: A Laboratory and Lecture Course for First Year Students of Electrical Engineering, Based on the International Definitions of the Electrical Units, Volume 1

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Cassell, limited, 1897 - Electricity - 643 pages
 

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Page 593 - As a unit of resistance, the international ohm, which is based upon the ohm, equal to 109 units of resistance of the Centimeter-Gramme-Second System of electro-magnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice 14-4521 grammes in mass, of a constant cross-sectional area, and of the length of 106-3 centimeters.
Page 593 - Ampere, which is one-tenth of the unit of current of the CGS system of electromagnetic units and which is represented sufficiently well for practical use by the unvarying current which, when passed through a solution of nitrate of silver in water, in accordance with a certain specification, deposits silver at the rate of 0.001118 of a gramme per second.
Page 599 - It is convenient to arrange the mounting so that the cell may be immersed in a water bath up to the level of, say, the upper surface of the cork. Its temperature can then be determined more accurately than is possible when the cell is in air. In using the cell sudden variations of temperature should as far as possible be avoided.
Page 594 - Victoria, by virtue of the power vested in Her by the said Act, by and with the advice of Her Privy Council, was pleased to approve the several denominations of standards set forth in the Schedule thereto as new denominations of standards for electrical measurement.
Page 25 - It is then rinsed successively with distilled water and absolute alcohol and dried in a hot-air bath at a temperature of about 160° C.
Page 597 - Materials. 1. The Mercury. — To secure purity it should be first treated with acid in the usual manner, and subsequently distilled in vacuo. 2. The Zinc. — Take a portion of a rod of pure redistilled zinc, solder to one end a piece...
Page 468 - ... acid. The crystals should be dissolved with the aid of gentle heat, but the temperature to which the solution is raised should not exceed 30° C.
Page 469 - Then insert the cork and zinc rod, passing the glass tube through the hole prepared for it. Push the cork gently down until its lower surface is nearly in contact with the liquid. The air will thus be nearly all expelled, and the cell should be left in this condition for at least 24 hours before sealing, which should be done as follows:— Melt some marine glue until it is fluid enough to pour by its own weight, and pour it into the test tube above the cork, using sufficient to cover completely the...
Page 596 - C. After cooling in a desiccator it is weighed again. The gain in weight gives the silver deposited. To find the current in amperes, this...
Page 468 - ... paste for an hour at this temperature, agitating it from time to time, then allow it to cool ; continue to shake it occasionally while it is cooling. Crystals of zinc sulphate should then be distinctly visible, and should be distributed throughout the mass ; if this is not the case, add more crystals from the stock bottle, and repeat the whole process. This method ensures the formation of a saturated solution of zinc and mercurous sulphates in water. To set up the Cell. The cell may conveniently...

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