Signedhandwritten over tube: KOHLRAUSH SPRING AMMETER / CARNEGIE GC E706
Inscribedon scale: N° 18835
base numbered: 23201
base near coil: 3201
FunctionIn Kohlraush spring ammeters, the electricity circulating around the coil creates an electromagnet which has a strength that is proportional to the current. An iron rod attached to a spring inside the long tube is pulled downward by the electromagnet, bringing the instrument's pointer down with it.
For a more detailed description of this type of ammeter, see a similar instrument at the University of Innsbruck's Experimental Physics Museum here.
Historical AttributesFrom old instrument card: "Belonged to Prof. Wm. Richards (1891- ca. 1925)". Theodore William Richards was a Harvard University professor who won the Nobel Prize.
ProvenanceFrom the Department of Chemistry, Harvard University.