reflecting galvanometer with suspended needle

Images(4)

reflecting galvanometer with suspended needle

Date1900-1920

Inventory Number0144a,b

ClassificationReflecting Galvanometer

Subject

User Department of Physics, Harvard University founded 1884

Cultural Region

Place of Use

Dimensions31.5 × 11 × 9.3 cm (12 3/8 × 4 5/16 × 3 11/16 in.)

Material

DescriptionGalvanometer with small flat bar magnet fastened to the center of a mica air damping disk, hung on silk thread with mirror. Two single coils (0144b) on each side of disk encased in cylindrical coil covers mounted on a rectangular nickel case (0144a) with oval viewing window for mirror and nickel suspension tube (needle and mirror missing). One pair of binding posts on both sides of cylindrical coil cover and two grounding terminals on front of case below viewing window. Cover and coils are detachable. Tripod base with three leveling screws. Similar to object 0145.

Signedunsigned

FunctionThis galvanometer measures small current displacements with a compass needle attached to a small mirror and magnet suspended on a silk thread from the top of a suspension tube (mirror and needle are missing). When the needle and mirror are mounted between the two coils and an electric current is passed through the coils, it induces a magnetic field that causes the coils to rotate in proportion to the current deflections, twisting the suspended magnet and mirror. The current deflections can then be detected using a light beam that reflects off the mirror and onto a scale.

ProvenanceFrom the Department of Physics, Harvard University, 11/20/1956.