Shunt (electrical)

In electronics, a shunt is a device which allows electric current to pass around another point in the circuit by creating a low resistance path. The term is also widely used in photovoltaics to describe an unwanted short circuit between the front and back surface contacts of a solar cell, usually caused by wafer damage. The origin of the term is in the verb 'to shunt' meaning to turn away or follow a different path.

One example is in miniature Christmas lights which are wired in series. When the filament burns out in one of the incandescent light bulbs, the electrical resistance becomes very high. The much higher voltage that this creates (equal to the full line voltage rather than the normal voltage divider level) causes the shunt to short out (becoming an antifuse) and become part of the circuit, again allowing electricity to pass and the set to light. If too many lights burn out however, a shunt will also burn out, requiring the use of a multimeter to find the point of failure.

A gas-filled tube can also be used as a shunt, particularly in a lightning arrestor. Neon and other noble gases have a high breakdown voltage, so that normally current will not flow across it. However, a direct lightning strike (such as on a radio tower antenna) will cause the shunt to arc and conduct the massive amount of electricity to ground, protecting transmitters and other equipment.

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