Laboratory Work in Electrical Engineering (preliminary Grade): A Series of Laboratory Experiments for First and Second Year Students of Electrical Engineering

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D. Van Nostrand Company, 1906 - Electric engineering - 218 pages
 

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Page 189 - 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 194 - 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 nsing the cell sudden variations of temperature should as far as possible be avoided.
Page 191 - ... made. Contact is made at the key, noting the time of contact. The current is allowed to pass for not less than half an. hour, and the time at which contact is broken is observed.
Page 189 - 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 192 - ... carefully removing any loose pieces of the zinc. Just before making up the cell dip the zinc into dilute sulphuric acid, wash with distilled water, and dry with a clean cloth or filter paper. 3. The Zinc Sulphate Solution. — Prepare a saturated solution of pure...
Page 193 - Clean the glass tube and platinum wire carefully, then heat the exposed end of the platinum red-hot, and insert it in the mercury in the test tube, taking care that the whole of the exposed platinum is covered. Shake up the paste and introduce it without contact with the upper part of the walls of the test tube, filling the tube above the mercury to a depth of rather more than 1 centimeter.
Page 193 - 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...
Page 190 - when on reversing the current in the fixed coils the change in the forces acting upon the suspended coil in its sighted position is exactly balanced by the force exerted by gravity in Westminster upon the iridio-platinum weight marked A, and forming part of the said instrument.
Page 193 - Keep the 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 insures the formation of a saturated solution of zinc and mercurous sulphates in water.
Page 192 - Care must be taken that the clock used is keeping correct time during this interval. The solution is now removed from the bowl and the deposit is washed with distilled water and left to soak for at least six hours. 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. After cooling in a desiccator it is weighed again. The gain in weight gives the silver deposited. To find the current in amperes, this weight, expressed...

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