When the switch is opened in fig. 2 the current drops rapidly. The inductor resists the drop in current by developing a very large induced voltage of polarity in the opposite direction of the battery, positive at the lower end of the inductor and negative at the upper end. This voltage pulse, sometimes called the inductive "kick", which can be much larger than the battery voltage, appears across the switch contacts. It causes electrons to jump the air gap between the contacts, causing a momentary electric arc to develop across the contacts as the switch is opened. The arc continues until the energy stored in the inductor's magnetic field is dissipated as heat in the arc. The arc can damage the switch contacts, causing pitting and burning, eventually destroying them. If a transistor is used to switch the current, for example in switching power supplies, the high reverse voltage can destroy the transistor.