Answer: Damaged Electronics

When an electrical component is damaged by overheating or an electrical short, it’s typical to see a puff or wisp of smoke escape the component as it burns up. This visible effect of a rather unfortunate event led to electrical engineers referring to the smoke as “magic smoke” or “factory smoke” in a joking fashion, as once the magic smoke was out the component no longer worked. The joke hinges on a logical fallacy, post hoc ergo propter hoc, in that it implies the device operated because of the smoke, and the release of the smoke caused the device to fail.