Description

Type P wall galvanometer. The instrument is a black metal box mounted to a wood board, and the wood board is attached to a black metal stand. The instrument has a glass rectangualr window that reveals the central chamber, which has a small cicular mirror attached to a metal coil. The mirror and coil are suspended by a thin wire at the top and a spring at the bottom. The wire tension is adjusted by the rod above the instrument. Front of instrument is stamped with "Leeds and Northrup Co Philadelphia."

Mirror galvanometers measure the strength of an electric current. When a current passes through the instrument (via the two connectors on the base), the current passes through the cord that suspends the mirror, twisting it slightly. When a light is shined on the mirror, the twisting causes the reflected light to move. The position of that reflected light on a graduated scale indicates the current running through the instrument. At the time they were invented, these galvanometers were more sensitive than other similar instruments, and were used to sense very weak currents. Instruments like these were also used in physics classrooms to demonstrate electrical principles. This instrument was used in the Simmons University physics department.