Paper, 'On the lifting power of electromagnets and the magnetisation of iron' by Shelford Bidwell

Description

Bidwell writes: 'I believe that no very recent investigations have been made with reference to the maximum lifting power which an electromagnet is capable of exerting, and the experiments conducted by Joule between the years 1839 and 1852 still form the basis of most of our practical knowledge on the subject. It is a matter of common experience that if an electromagnet be excited by a gradually increasing current a limit is soon reached, beyond which the ratio of increase of sustaining power to increase of current becomes rapidly smaller; and it has generally been assumed that this ratio continues to diminish indefinitely, so that an infinite current would not impart to a magnet much greater lifting power than that which it possesses when an approach to saturation is first indicated.'

Annotations in pencil and ink. Includes four graphs of experimental results.

Subject: Magnetism

Received 6 May 1886 / 14 May 1886 / 1 June 1886. Read 10 June 1886. Communicated by Lord Rayleigh [John William Strutt].

A version of this paper was published in volume 40 of the Proceedings of the Royal Society as 'On the lifting power of electromagnets and the magnetisation of iron'.

Reference number

PP/8/31

Earliest possible date

1886

Physical description

Ink and graphite pencil on paper

Page extent

29 pages

Format

Manuscript
Diagram