Electrical Technology

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Pitman, 1924 - Electric engineering - 376 pages
 

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Page xi - As a unit of resistance, the international ohm, which is based upon the ohm equal to 10" units of resistance of the CGS system of electromagnetic 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 grams in mass, of a constant cross-sectional area and of the length of 106.3 centimetres.
Page 353 - The instrument torque is proportional to the product of the currents in the fixed and movingcoil systems at any instant, and is therefore proportional to the instantaneous product of line voltage and load current.
Page 361 - But both fields are proportional to the current in the magnet coil, and therefore the torque is proportional to the square of the current or voltage to be measured.
Page 162 - A circuit includes two sections AB and BC in series. The section AB consists of two branches in parallel. The first of these is formed of a non-inductive resistance of 60 ohms in series with a condenser of 50 microfarads, whilst the second consists of a resistance of 60 ohms having an inductance of 250 millihenries.
Page 69 - This motor drives a fan which requires 300 hp at the full-load speed of the motor. The torque required to drive the fan varies as the square of the speed. What resistances should be connected in series with each slip ring so that the fan will run at 300 rpm?
Page 35 - The brushes of the same polarity are connected together, and therefore the armature winding is divided into four paths in parallel. In general, the number of parallel paths through a lap winding is equal to the number of poles ; the terminal EMF is equal to the EMF induced in one parallel path ; the current delivered to the external circuit is equal to the current in each armature conductor multiplied by the number of parallel paths.
Page 143 - Standard deviation is a measure of dispersion in a frequency distribution equal to the square root of the mean of the squares of the deviations from the arithmetic mean of the distribution.
Page 363 - Thus, the speed of the disc is proportional to the power, and the number of revolutions made by the disc in a given time, proportional to the expression / W . dt, that is, to the energy.

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