Natural philosophy for general readers and young persons / translated and edited from Ganot's Cours élémentaire de physique (with the author's sanction) by E. Atkinson.

  • Atkinson, E. (Edmund), 1804-1887.
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Natural philosophy for general readers and young persons / translated and edited from Ganot's Cours élémentaire de physique (with the author's sanction) by E. Atkinson. Source: Wellcome Collection.

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    and contrary quantities of electricity in the wire, the two currents neutralise each other. If a galvanometer is placed in the circuit, only a very feeble deflection is produced in the direction of the direct current. This is not the case if the two extremities, P and P', of the wire are separated. As the resistance of the air is then opposed to the passage of the currents, that which has most tension, that is, the direct one, passes in excess, and the more so the greater the distance of P and P', up to a certain limit, at which neither passes. There are then at P and P' nothing but tensions alternately in contrary directions. The effects of the coil, like those of the battery, may be classed under the heads physiological, chemical, heating, hanitwus, me- c]ia7iical ; they have this difference, that they are enormously more intense. The physiological effects of Ruhmkorffs coil are very powerful ; in fact, the shocks are so violent that many experimenters have been suddenly prostrated by them. A rabbit may be killed with an induction current arising from two of Bunsen's elements, and a somewhat larger number of couples would kill a man. The heating effects are also easily observed ; it is simply neces- sary to interpose a very fine iron wire between the two ends, P and P', of the induced wire ; this iron wire is immediately melted, and burns with a bright light. The spark of the Ruhmkorff's coil is used to fire mines in military and mining operations. The chemical effects are very varied, inasmuch as the apparatus produces both the ordinary effects of the currenc and of electricity in a high state of tension. Thus, according to the shape and distance of the platinum electrodes immersed in water, and to the degree of acidulation of the water, either luminous effects may be produced in water without decomposition, or the water may be decomposed and the mixed gases disengaged at the two poles, or the decomposition may take place, and the mixed gases separate either at a single pole or at both poles. The luminous effects of Ruhmkorff's coil are also x&xj remark- able, and vary according as they take place in air, in vacuo, or in very rarefied vapours. In air the coil produces a very bright loud spark, which, with the largest-sized coils, has a length of eighteen inches. In vacuo the effects are also remarkable. The experiment is made by connecting the two wires of the coil, P and P', with the two rods of the electrical egg (fig. 369), used for producing in vacuo the luminous effects of the electrical machine. A vacuum