| Reference number | PP/4/7/1 |
| Previous numbers | PP/36/7 |
| Level | Item |
| Title | Manuscript, 'On the production of transient electric currents in iron and steel conductors by twisting them when magnetised, or by magnetising them when twisted' by J A [James Alfred] Ewing |
| Date | 1882 |
| Description | Ewing writes: 'A chance observation, made in the summer of 1881, drew my attention to the fact that when the ends of an iron wire are connected to the terminals of a galvanometer, a transient current will be observed if the wire he suddenly magnetised while it is held in a state of torsion, or suddenly twisted whilst in a state of longitudinal magnetisation. Further inquiry showed that these currents are satisfactorily explainable by reference to the results of more direct observations which have been made on the effects of stress on magnetism. They present, however, certain features of interest, and the examination of them, of which a condensed account is given below, may form a useful supplement to any direct investigation of the effects of stress on magnetic susceptibility and residual magnetism. 2. A straight, moderately soft, well-annealed iron wire, 1 millim. in diameter and 34 centims. long, was placed horizontally in an E. W. position, with one end securely fixed and the other held by a twisting arm, by which any desired amount of torsion might be applied. The twisting arm was provided with a pointer, which travelled over a graduated circular dial. The ends of the wire were connected by long leading wires to a Thomson’s mirror galvanometer of 0·25 ohm resistance, with a heavy mirror, which made it fairly suitable for ballistic work. Round the iron wire was a magnetising solenoid of 660 turns, 31 centims. long, in two layers, wound so as to have no longitudinal component parallel to the wire. In circuit with the solenoid was a single large Daniell’s cell and a reversing key. The resistance of this circuit was 1·36 ohms and, if we assume the electromotive force of the cell to have been 1 volt, the magnetising force was therefore 4π x 660/31 x 1 x 108/1·36 x 109 = 20 c. g. s. units very nearly.'
Annotations in pencil and ink. Includes four pages of diagrams of experimental apparatus and results.
Subject: Electromagnetism
Received 21 October 1882. Read 15 November 1883.
A version of this paper was published in volume 36 of the Proceedings of the Royal Society as 'On the production of transient electric currents in iron and steel conductors by twisting them when magnetised, or by magnetising them when twisted'. |
| Extent | 27p |
| Format | Manuscript |
| Physical description | Ink and graphite pencil on paper |
| Digital images | View item on Science in the Making |
| Access status | Open |
| Related material | DOI: 10.1098/rspl.1883.0084 |
Fellows associated with this archive
| Code | Name | Dates |
| NA8053 | Ewing; Sir; James Alfred (1855 - 1935); engineer and cryptographer | 1855 - 1935 |