Wheatstone Bridge Potentiometer. A wooden box with a brown Bakelite top with dials and rods fixed on top of it. On two sides (opposite of each other) of the wooden box are glass panels which make the interior of the box visible: various small coils formed of winds of brown-insulated wire attached in a pair of rings to the underside of the top of box.
On the Bakelite surface there are 12 metal terminals aligned along thee edges of the box. These are labelled “Std. Cell”, “A”, “B”, “C” “BATT.” and “GALV.” In the middle of the Bakelite surface there are three large ridged Bakelite knobs arranged in a row. From left to right, these are labelled “CIRCUIT SWITCH”, “VOLTS” and “RHEOSTAT”. The latter two have connected arrows which act as pointers on a circular arrangement of markings on the surface. Turning these two knobs turns apparatus inside the instrument among the circles of coils.
Next to these there is a flexible strip of metal above a metal peg; this can be depressed to touch the peg. This is labelled, “Std. Cell Key”.
Along one edge of the top, and next to the row of electrical terminals along the other, there are two metal rods with a metal block fixed around them; this can slide along the rod. Running alongside one (one wire) and underneath another (two wires) are wires which the block “carriage” just touches as it slides. Fixed to the Bakelite surface next to the metal rod close to the edge is a white ruler with a scale going from 0-101, marked in 10s. This is labelled: “0-100 = 0.1 VOLT”
Accession Number: 2009.ph.134
Alternative Name:
Metal: Copper Alloy, Metal: Unknown , Bakelite, Wood, Glass
Old inventory number on a paper tag = phy110.
On the Bakelite surface, engraved: “W.G. PYE & Co. ENG. CAMBRIDGE”; and “No. 7186”.
On the two shortest sides of the box “IIE” is painted in white lettering.
Dimensions (cm): Height = 12, Length = 40.3, Width = 26
Potentiometers are used to determine an unknown voltage (potential difference) through the comparison of a known voltage with an unknown voltage. This instrument was likely used by students in this capacity in the course of demonstrations and experiments.
Good: This instruments appears to have been well-used, but is intact. The box is in good condition although on one of the corners interlocking bits of wood are splitting. The glass windows are intact and the interior of the box looks as if it is in very good condition. The Kakelite surface is degrading and where metal is affixed to it, there is white residue. The tops of the electrical terminals are browned and oxidized; the enamel on the base of these is worn and scratched and where it is removed, the metal has oxidized. There is a chip out of one of the corners of the Bakelite surface.
Associated Instruments:
Manufacturer: W.G. Pye & Co, Cambridge
Date of Manufacture: 1893-1920
Provenance:
Compare this potentiometer with an example at Yale’s Peabody Museum, which is very similar but appears to lack the glass windows. [25/11/20]
Historical Notes: