Electrical Papers Volume 1
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 edition. Excerpt: ... work is done by E during the passage of Q, an amount EC is done per second. The supply of energy obviously comes from the galvanic cell, of which more later, whilst we now consider its destination. In W = EQ insert EC for E and Ct for Q, their equivalents when the circuit is conductively closed, and we obtain 1F=JICH in terms of resistance and current, as the amount of energy to be accounted for. The solution is supplied by Joule's discovery that with a steady current heat is continuously developed in a conductor, its amount being proportional to the square of the current and to the time it has been on. Hence, if U be the heat, expressed as energy to avoid the useless introduction of Joule's coefficient, we have H=F1CH, where B1 is a necessary quantity required to make Rfi-t be energy. Now BCH is energy, being the same as EQ, consequently M1 is resistance, and can therefore be only R multiplied by a mere numeric. But if no other work is done than in heating the wire, we must have H= W, the numeric = 1, and BX = B. Hence expresses Joule's law. Thus, in EC=RCi, which is the equation of activity, or rate of working in a galvanic circuit when the sole result is heat in the conductor, we may say that EC is the work done by E in driving C (true, whatever other effects than heat may be produced), and RC the equivalent rate of generation of heat. We may here advantageously reintroduce the mechanical analogy before employed, viz., a body set in motion by a constant force F, and opposed by a resisting force, rv, simply proportional to its velocity, v. So long as F is greater than rv there is acceleration of velocity, which must cease when F= rv, which equation consequently gives us the steady velocity. At the same time Fv is the activity of the applied...
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