English: Animation showing the operation of a Jacobs Ladder (Jakobsleiter), a high voltage entertainment display device. It consists of two metal rods in a shallow V shape, that gradually spread apart, connected at the bottom to the terminals of a high voltage transformer. When the power is turned on, a continuous electric arc appears at the bottom of the rods. Because the electricity heats the air, the arc rises, "climbing" the rods, getting longer as it goes up, until it gets to the top and the arc extinguishes. Then a new arc forms at the bottom and begins climbing. The voltages used are in the range 3000 - 15000 volts. Jacobs Ladders are sometimes seen in old science fiction movies.