spark arrester?

Also called a snubber - stops sparks - prevents interference with TVs and radios - prevents damage to electric motors.

Snubbers are frequently used in electrical systems with an inductive load where the sudden interruption of current flow often leads to a sharp rise in voltage across the device creating the interruption. This sharp rise in voltage is a transient and can damage and lead to failure of the controlling device. A spark is likely to be generated (arcing), which can cause electromagnetic interference in other circuits. The snubber prevents this undesired voltage by conducting transient current around the device.

A simple snubber comprises a small resistor in series with a small capacitor.

Peccavi
April 2010