|
Date: |
|
Description: | L.C.E. 90 (old departmental number in aluminium paint, removed) MANU Unsigned. circa 1910 DES after BRAUN,Karl,Ferdinand. 1901 Strasburg, Germany DES after DUNWOODY, Henry, Harrison,Chase,General 1890 The United States of Amrerica DES after PICKARD,Greenleaf,Whittier 1906 The United States of Amrerica Used to detect radio waves the crystal detector works on a principle discovered by Sir Oliver Joseph Lodge in 1890. When two metals are in poor contact they have a high initial resistance and when a weak radio signal passes through the system the resistance falls rapidly and a current flows. Materials that posses this quality are now called semiconductors This effect was used in the invention of the coherer by Edouard Branley in the same year whereby iron filings were placed between two electrodes in a glass tube. By tapping the tube the initial resistance is restored. Marconi used the coherer in his early radio telegraphy experiments his device had a small quantity of filings in an evacuated tube. The coherer was quickly superceded by the electrolytic and crystal detectors. The crystal detector has the advantage that the resisitance of the crystal automatically resumes its initial value without the need for a tapper. | 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 |
|
More Like this...
-
-
Coherer
none MANU ERSKINE-MURRAY,James Robert. circa…
-
-
-
-
-
-
-
-
|