If the two points of the electrodes touch and electricity is applied to them and immediately afterwards they are moved a few millimeters apart, the electricity continues to circulate, bridging the gap between the two points. They become incandescent, emit a strong white light and are joined together by a line of light, called an arc due to the shape it assumes, surrounded by a bluish halo.
When the lamp is powered by direct current the positive electrode emits more intense light.
The two carbons burn, since they are in the air and, albeit slowly, they shorten continueslly. If the points were fixed, the distance between them would increase and, once a certain limit was exceeded the lamp would go off. For this reason, the electrodes are regulated, either manually or automatically, as they are consumed, thus maintaining the proper distance between the points.
Following the announcement of the invention of the pile by Alessandro Volta (1745-1827) in an epistolary memorandum on 20 March 1800, the scientific world was pervaded by a great wave of enthusiasm and fervour and experimental activities addressed the question of establishing the nature of voltaic current. ...continues