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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    secondary wire (502), when it opens or closes, and hence it must be constantly interrupted. This is effected by means of the oscillating hammer, o, omitted in figure 443, but represented on a larger scale in fig. 444. In the centre of the bobbin is a bundle of soft iron wires, forming together a cylinder a little larger than the bobbin, and thus projecting at the end as seen at A., When the current passes in the primary wire, this hammer, 0, is attracted ; but immediately, there being no contact between 0 and /i, the current is broken, the magnetisation ceases, and the hammer falls ; the current again passing, the same series of phenomena recommences, so that the hammer oscillates with great rapidity. In proportion as the current passes thus intermittently in the primary wire of the bobbin, at each interruption an induced current, alternately direct and inverse, is produced in the secondary wire. But as this is perfectly insulated, the current acquires such an intensity as to produce very powerful effects. Fizeau increased this intensity by interposing a cotidenser in the induced circuit. As constructed by Ruhmkorff, for his largest apparatus, it consists of 150 sheets of tinfoil about 18 inches square; these sheets being joined are coiled on two sides of a sheet of oiled silk, which insulates them, forming thus two armatures ; they are then coiled several times round each other, so that the whole can be placed below the helix in the base of the apparatus. One of these armature?, the positive, is connected with the binding screw, ?, which receives the current on emer^jing from the bobbin ; and the other, the nega- tive, is connected with the binding screw, which communicates by the plate, K, with the commutator, C, and with the battery. 506. Effects produced by Ruhmkorff's coil—The high degree of tension which the electricity of induction coil machines possesses has long been known, and many luminous and calorific effects have been obtained by their means. But it is only since the improvements which Ruhmkorff has introduced into his coil, that it has been possible to utilise all the tension of induced currents, and to show that these currents possess the properties of statical as well as dynamical electricity. Induced currents are produced in the coil at each opening and breaking of contact. But these currents are not equal either in duration or in tension. The direct current, or that on opening, is of shorter duration, but more tension ; that of closing of longer duration but less tension. Hence if the two ends, P and P', of the fine wire (figs. 443 and 444) are connected, as there are two equal