Figure 1. Tangent Galvanometer
Brief: The Galvanometer is a device used to detect the electric current flowing through an object. The current disrupts the magnetic field in the coil of the device. The word galvanometer was first attributed to Luigi Galvany in 1836 when he realized that the electric current would make a dead frog's leg jerk. The earliest galvanometer relied on Earth's magnetic polarity to reset the device after every use. Eventually improvements led the galvanometer to its final form as the Mirror galvanometer. This device was designed by William Thomson (Lord Kelvin) uses permanent magnets hung by a thread between a coil with a mirror affixed to the magnets. The light would bounce of the mirror onto a scale when a current would displace the magnets holding the mirror.
