mirror galvanometer

This video on the Mirror Galvanometer begins with a brief and informal account of the origin of ‘current electricity’ – as opposed to ‘static electricity’. The latter, along with magnetism, had been known for many centuries, and extensively studied. It is suggested that only with the discovery of constant electric current through a conductor, did the Modern Era of electricity began. Current electricity commenced with Volta, ca. 1800, and several examples are given on new discoveries immediately made, as the electric current was quickly investigated. In particular, the quest to quantify the flow of electricity is outlined, with particular reference to the measurement of very small currents – as needed by the great venture of transatlantic telegraph cables. A demonstration of the mirror galvanometer is given, using a modern laser pointer as a light source. This results in a current of 0.05 microamps producing a perceptible deflection of the mirror galvanometer light spot at a distance of around 45 feet (13.7m). The presentation concludes with a brief extract from a historic speech recording made in 1907 by Lord Kelvin (1824-1907).

For a truly stupendous amount of information on transatlantic (and other) telegraph cables, besides electric telegraphy as a whole, see http://atlantic-cable.com//

Acknowledgements of images used:

Voltaic Pile:
By I, GuidoB, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2249821

Humphry Davy:
https://commons.wikimedia.org/w/index.php?curid=6364758

Lord Kelvin:
By "Photo by Messrs. Dickinson, London, New Bond Street" (according to http://www.sil.si.edu/DigitalCollections/hst/scientific-identity/fullsize/SIL14-T002-07a.jpg) - http://www.sil.si.edu/digitalcollections/hst/scientific-identity/CF/by_scientist_display_results.cfm?scientist=kelvin, Public Domain, https://commons.wikimedia.org/w/index.php?curid=376221

We may inadvertently have omitted other credits; these will be corrected if we are informed of such omissions.

Видео mirror galvanometer канала Norman Field