The concept of ‘electric field’ was introduced in the 19th century by the English researcher Michael Faraday (1791-1867). This demonstration apparatus shows that the form of the electric field determines the path of the spark discharge. Three adjustable brass components are mounted on a vertical glass tube: a ball, a ring and a segment of a sphere. Each of these components can be connected to a high alternating voltage. If, for example, the ball and the segment of a sphere are arranged in such a way that their centres coincide, then the electric field is the same in all directions: the sparks leap everywhere. If the segment is at a larger distance, the field is strongest at the edge: the sparks leap only there. If the segment is at a very small distance, the spark arc is formed in the centre.
Discharger
circa 1850 - 1874