A device for detecting electric charge is called an electroscope. The simplest electroscope consists of a metal rod, at one end of which strengthened the ball, а на другом — two leaves of metal foil (rice. 14.6).

The rod of the electroscope goes through a tube of a dielectric material and placed in a glass or plastic container, which protects the leaves from the impact of the movement of ambient air. Если заряженным телом касаются ball electroscope, it leaves diverge at an angle, since they are charged the same name.

Sometimes in experiments you must have a charged electroscope, the sign of the charge which must be known in advance. In this case, it is charged by contact with either a glass rod, grated skin (while glass is positively charged), or ebony wand, rubbed with fur (the ebony in this case, negatively charged). Такой заряженный электроскоп можно использовать для определения знака заряда произвольно наэлектризованного тела.