Electric and Magnetic Measurements and Measuring Instruments

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McGraw publishing Company, 1907 - Electric measurements - 398 pages
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Page 179 - ... equalize the strain. The rotation of d, of course, carries g with it, and g, in moving, causes the silk fiber to rotate the shaft which carries the needle. If the temperature of the air surrounding the instrument changes, a and b are affected alike, and their...
Page 1 - ... to it a quantity of 1 international coulomb. International Ohm. — Practical unit of resistance, representing' the resistance offered to an unvarying current of electricity by a column of pure mercury at the temperature of melting ice having a mass of 14-4521 grammes, a constant cross-section, and a length of 106-3 centimetres.
Page 3 - The liquid should consist of a neutral solution of pure silver nitrate, containing about 15 parts by weight of the nitrate to 85 parts of water. The resistance of the voltameter changes somewhat as the current passes. To prevent these changes having too great an effect on the current, some resistance besides that of the voltameter should be inserted in the circuit. The total metallic resistance of the circuit should not be less than 10 ohms.
Page 344 - The intensity or strength of a magnetic field at any point, is measured by the force it will exert on a unit magnetic pole.
Page 52 - ... rotated. As the two coils and commutator are rotated in the direction indicated by the arrows, the two brushes rub against the segments consecutively and always make contact with the two opposite ones. The brushes...
Page 343 - ... conductor will act on a unit pole at the center of the arc to which the conductor is bent with a force of one dyne. Thus the absolute value of one CGS unit of current may be determined. 2460. When a magnetic pole is placed near another magnetic pole, the attraction (or repulsion) of the two poles is proportional to the product of the strengths of the two poles, and inversely proportional to the square of the distance between them ; so, two equal magnetic poles, which, when placed at a unit distance...
Page 4 - ... themselves in curved lines similar to those of Fig. 2; while, if the return circuit of the conductor be also poked through the card, the filings assume the alignment shown in Fig.
Page 47 - Their magnetic strength depends upon the size and permeability of the core, the number of turns of wire in the coil, and the strength of the current in it.
Page 179 - ... equilibrium can be restored only when the pulley d rotates sufficiently to again equalize the strain. The rotation of d, of course, carries g with it and g in moving, causes the silk...
Page 387 - Because the voltage induced in the secondary winding is proportional to the rate of change of the flux enclosed by that winding, the induced voltage is low.

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