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 atlantic-cable....
Acknowledgements of images used:
Voltaic Pile:
By I, GuidoB, CC BY-SA 3.0, commons.wikime...
Humphry Davy:
commons.wikime...
Lord Kelvin:
By "Photo by Messrs. Dickinson, London, New Bond Street" (according to www.sil.si.edu/...) - www.sil.si.edu/..., Public Domain, commons.wikime...
We may inadvertently have omitted other credits; these will be corrected if we are informed of such omissions.

[@borisromanoff4244]

A wondeful lecture! Congratulations!

[@bixanorak]

Thanks for writing! It rambles on a lot, but gets there in the end... Cheers, Norman.

[@robertfenney]

Excellent video!

[@bixanorak]

Thanks & glad you enjoyed it. Cheers, Norman.

[@ItsRonsway]

as always very interesting video

[@RWBHere]

Nice touch at the end of a very interesting history lesson, Norman. Thank-you. Mirror Galvanometers are surprisingly accurate indicators, for something which was developed so long ago. We had a couple at Plymouth Poly, which were made pre-1900. Microamps could be measured with ease, using an ordinary white light source, even with a beam of only a metre or so. But they took several seconds to settle down, because the high levels of damping used.
The Kelvin recording reminds me that the oldest recording I've ever heard 'live' was a cylinder of 'The Charge Of The Light Brigade', being read by Tennyson. It was on a cylinder, recorded somewhere in the late 1880's to 1890. Quite an experience to hear it recited in the way in which he intended it to be read.

[@82abn34]

Thank You! Greetings from Ferndale WA, USA.

[@borisromanoff4244]

herr professor: sorry I had no good professors as you are during my college years. thanks Lord it is never late to start learning again.

[@ianhand5006]

Very interesting!

[@bixanorak]

Many thanks & glad you liked the video. More coming! Cheers, Norman.

[@monikapho5673]

very intersecting viedo

[@borisromanoff4244]

herr professor: you are great. you are a born professor. I do like your "classes". you are as good as your partner, professor ludwig von drake.

[@transformingArt]

Fascinating. Thank you for posting this. Also, I didn't realize Lord Kelvin made a recording! Where can I hear the full version?

[@bixanorak]

Thanks for writing. Alas, the Kelvin recording is very poor quality. If you email me via www.early78s.uk I'll explain about it. All the best for now, Norman.

[@RWBHere]

Alexander Graham Bell's assistant made a recording, in which he tells the story of the serendipitous invention of the telephone. It's available online. Do you want to make a video about that subject, Norman?