|
Date: |
|
Description: | 1 (Kelvin ?bequest 1893 in red cellire). K.E.4. (Green and Lloyd catalogue number in white paint). DES THOMSON,William,Lord,1st Baron Kelvin of Largs. circa 1869 Glasgow, Scotland. MANU J. White. circa 1869 Glasgow, Scotland. This electrometer is a development of the attracted disc type of instrument. The attracting plate sits on top of three insulating glass rods. It is a small square of fine aluminium on the end of a lever which sits at the centre of a thin guard plate which projects about 3cm from the upper attracting disc to prevent the operator's hair being attracted causing the operator to receive a shock. The attracted plate is part of a simple balance that is viewed through a small lens. This assembly and the guard plate are moved up or down using the screw thread which has about 200 turns.
Kelvin claimed that this instrument could measure electric potentials from 0 to that of a conductor which could generate a spark of 12 inches which is approximately 400 kv, depending on the atmospheric coditions.
Kelvin claimed that a glass cover was not necessary since the instrument was not susceptible to normal air currents, lthough not to sudden changes such as those produced by a door opening or closing. However, in 1870 he noted his intention to add a glass shade because of difficulties experienced in measuring high tension due to dust and shreds. It is not known if a shade was made but it could not have been fitted to the existing base. This instrument was used by the Reverend John Kerr in his researches into the photoelectric effect. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
|
|