An electrical arc is one of the more power packed events you will find. Controlled, it can be very useful. Uncontrolled, the risks of the arc are practically unlimited.
An electrical arc is defined as the jumping of an electrical current through a non-conducting element such as air or gas. When an arc occurs, the resulting voltage is quite high creating a great deal of heat. Controlled arcing is used to cut or melt metals. An arc welder is an example of controlled arcing. A lightening bolt is an example of uncontrolled arcing. The tremendous amount of energy and voltage contained in a lightening bolt illustrates the danger of an arc. An uncontrolled arc can also occur in a home wiring system or within the wiring of an appliance. This situation has a great potential for damage.
The actual physics behind the arc is quite complicated and has to do with the conductive and insulating properties of gas and air. Although air is normally a good insulator, when air is stressed by sudden high voltage, it can break down and become conductive causing a sudden electrical current flow. This process is called electrical breakdown. Again, controlled electrical breakdown is used quite often. The spark plug of an automobile is another example. When the controlled arc is of very low pressure, it can be used in several beneficial ways such as exciting the gas in a fluorescent lamp.
In an uncontrolled event, such as a short in an exposed wire or a failure of insulation, the sudden increase in voltage is controlled by a circuit breaker. The purpose of the circuit breaker is to open when a certain voltage limit is exceeded. This effectively stops the flow of electricity completely and will keep an arc from forming or continuing. If the circuit breaker fails, however, an arc forms. The extreme heat generated by the arc will melt insulation, damage components and worst of all; will create a serious fire hazard. Even the smallest arc has the potential to generate sufficient heat to ignite any nearby flammable substance.
The Consumer Product Safety Commission reported that in 1997 there were 40,300 home fires caused by arcing from bad extension cords, faulty outlets, frayed wires, or loose electrical connections. These fires resulted in 230 deaths, 1,300 injuries, and 687.3 million dollars of property damage. These figures point out the need for inspections and testing of electrical wiring and connections within the home. It is of utmost importance to maintain a home electrical system. This includes properly working and properly rated circuit breakers. It is also important to follow common sense electrical advice such as not overloading outlets and extensions cords.
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