Shunt (electrical)

In electricity, a shunt is a device which allows electrical current to pass around another point in the circuit.

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 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 an AC detector 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.

Other circuits use diodes or even plain resistors as shunts.