On the induction apparatus / by N.J. Callan.

  • Callan, N. J. (Nicholas Joseph), 1799-1864.
Date:
1857
Catalogue details

Licence: Public Domain Mark

Credit: On the induction apparatus / by N.J. Callan. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    duced iu the secondary coil, which is the result of the combined action of three inductive forces arising from the suspension of the magnetism of the core, of the primary and of the secondary coil. When the secondary coil is made of iron wire, the mag- netic power it will receive from the primary current, and from the magnetic inductive force of the core, will be far greater than if it be made of copper wire; and therefore the intensity of the secondary current in a coil of iron wire must be much greater than that of the secondary current in a coil of copper wire. I showed, at the late meeting of the British Association in Dublin, an induction coil in which the secondary wire was of iron: its length was about 21,000 feet, and its thickness about the y^^dth of an inch. With a single cell, 6 inches by 4, and without a condenser, this coil gave sparks half an inch long. Should a condenser of the proper size increase the length of the sparks, as it does in Mr. Gassiot’s great coil, in a thirtyfold ratio, my coil ought to give sparks 15 inches long with a single cell. I have not yet tried it with a condenser: I made two large condensers, in which, when both were united, the acting surface of each plate exceeded 600 square feet. After being used for some time, the insulation of the plates gave way, and the action of the con- denser became feeble, and once ceased altogether. I intend to reconstruct both condensers as soon as possible, and to try their effect on the coil, on which I have, since the meeting of the Association, coiled about 28,000 feet more of fine iron wire, so that at present the length of the secondary coil is nearly 50,000 feet. Since the increased length of wire was put on the coil, I have got from it, with a single cell, 6 inches by 4, and without a condenser, sparks yf ths of an inch in length. I expect that with the same battery it will give sparks at least an inch long without a condenser. This is, I believe, the most powerful coil ever made. The second result is, that if a bundle of iron wire be put into a coil of insulated thick copper wire connected with a battery, the quantity of electricity which will flow through another coil in contact with the same battery, will be considerably greater when the iron wires are in the first coil than when they are altogether or partly removed. This T found by using a contact- breaker worked by an electro-magnet, the helix of which was connected with the same battery by which an induction coil was excited. In trying the effect of the induction coil without an iron core in its primary coil, I found that the action of the elec- tro-magnet of the contact-breaker was slow and feeble. When a few wires were put into the primary coil, the action of the contact-breaker was sensibly increased; and when the primary coil was filled or nearly filled with wire, the attraction of the electro-magnet became considerably stronger, and consequently