Electrical contacts Electrical contacts An electrical contact is an electrical circuit component found in electrical switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, usually metal. When a pair of contacts touch, they can pass an electrical current with a certain contact resistance, dependent on surface structure, surface chemistry and contact time; when the pair is separated by an insulating gap, then the pair does not pass a current. When the contacts touch, the switch is "closed"; when the contacts are separated, the switch is "open". The gap must be an insulating medium such as air,
Electrical room unauthorized persons; these rules are especially strict where equipment within the room has exposed live terminals. Regulations may require two separate means of exit from a room where the power rating of circuits exceeds some threshold, to allow for quick exit in an emergency. Rooms containing oil-filled equipment may be required to have fire-resistant construction or active fire suppression equipment in the room and may be designated as an "electrical vault". Since power distribution often requires large numbers of electrical cables, special measures for fire resistance of cables and cable trays may be also specified by regulations. In industrial buildings