Sangeetha Pulapaka

An electroscope is a traditional device for measuring electric charge. Initially, a metallic rod with a negative charge is moved until it touches a metal sphere. The electrons flow though an insulated metallic bar that is distributed between two thin (usually gold) leaves that repel each other. They separate in proportion to the charge.

 The first electroscope, a pivoted needle called the versorium, was invented by British physician Willliam Gilbert around 1600.The pith-ball electroscope and the gold-leaf electroscopeare two classical types of electroscope that are still used in physics education to demonstrate the principles of electrostatics A type of electroscope is also used in the quartz fiber radiation diameter. Electroscopes were used by the Austrian scientist Victor Hess in the discovery of cosmic raysElectroscopes detect electric charge by the motion of a test object due to the Coulumb - electrostatic force. Since the electric potential  or voltage  of an object with respect to ground equals its charge divided by its capacitance to ground, an electroscope can be regarded as a crude voltmeter.