The Spot Reflecting Galvanometer is a laboratory instrument used to measure small currents with high precision. It consists of a coil suspended in a magnetic field and a small mirror attached to the coil. When a current flows through the coil, it produces a magnetic field that interacts with the external magnetic field, causing the coil to rotate.

The rotation of the coil is reflected in the mirror, which produces a light spot on a distant scale. The deflection of the spot is proportional to the current flowing through the coil. The instrument is designed to be highly sensitive and is used in a variety of experiments involving electrical currents.