# Principles of Electrical Engineering

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...for this change to take place. Then the average e. m. /. induced in the circuit during this interval is numerically E =-----provided each line of induction links each turn, and therefore the average value of the induced current is R Rt or /f N R But /t is the quantity of electricity which flows through the circuit in this interval. Hence the important relation that, when the number of lines of induction linking a coil of N turns is changed by an amount--cf2, a quantity of electricity Q_(cf-cf, ) N (5) R is transferred across each section of the wire forming the circuit, where R is the total resistance of the circuit, where all quantities are in c. g. s. units. Hence, if when a coil which forms part of a circuit which has a total resistance of R abohms is pulled quickly out of a magnetic field, a quantity of Q abcoulombs of electricity is " discharged" through the circuit, the number of lines of induction in maxwells which threaded the coil when it was in the field is (5a) Or, if the coil is reversed in the field (i.e., turned 180 degrees about any axis in the plane of the coil), or if the direction of the field through the coil is reversed, the number of lines of induction in maxwells originally threading the coil is When a momentary current is established in a galvanometer of which the moving element is fairly heavy and has a long period of vibration, it can be shown that the momentary force or impulse produced on this element causes it to swing out from its position of equilibrium by an amount which is approximately proportional to the quantity of electricity discharged through the galvanometer. Hence, if the coil we have just been considering is connected in series with such a long period or ballistic galvanometer, and the...