tangent galvanometer
Date: 1850-1900
Inventory Number: 1997-1-1125
Classification: Tangent Galvanometer
Subject:
Maker: American ?
User: Department of Physics, Harvard University (founded 1884)
Cultural Region:
City of Use:
Dimensions:
45 × 41 × 30 cm (17 11/16 × 16 1/8 × 11 13/16 in.)
Description:
Tangent galvanometer with compass in circular glass-topped brass case. Etched brass scale is graduated from 0-90-0 and compass supported on wooden column with horizontal wooden radius surrounded by large fixed coil with 9 turns of heavy wire wound in painted black brass ring. Ring has five binding posts with plastic knobs not original to instrument. Circular wooden base with two leveling screws. See 0202 and 0544 for similar meters.
Signedunsigned
FunctionA tangent galvanometer measures the strength of an electric current. It has a circular coil with a turn of wire and a magnetic needle at the center that is either balanced on a point or suspended by a fiber of silk or quartz. The meter has to be first aligned in the north-south direction and thus the instrument takes into account the earth's magnetic field. When a current is sent through the coil, the needle is deflected according to the vector sum of the field produced by the earth and by the unknown current in the coil. The tangent of the needle's angle of deflection is proportional to the strength of the unknown current producing it.
For more information, go to the following website.
For more information, go to the following website.
Curatorial RemarksUsed in classroom demonstration and probably altered. Red and black plastic knobs appear recent. See 0544 for similar instrument.