GALVANOMETER

an instrument for detecting, or measuring the strength of, an electric current. There are various forms of instruments suitable for different purposes, the chief being the sine, tangent, mirror, suspended coil, and ballistic g’s. The last is used for measuring the quantity of electricity that has pa ed in the case of a current of very short duration, while the mirror g. will detect and measure very weak currents. The construction of all g’s depends on the observed fact that an electric current in a wire deflects a neighboring magnetic needle in accordance with a known law.