Can a DC voltage be used to trigger a triac?

A triac is a device used to control power in AC circuits, but it can also be triggered by a DC voltage under specific conditions. The correct answer indicates that a DC voltage can indeed trigger a triac, but it must be done constantly. This is because triacs require a continuous gate signal to remain in the conducting state once they are triggered. If the gate signal is momentary, the triac will turn off once the current drops below a certain level, which would not be practical for sustained control.

Using a constant DC voltage allows the triac to latch on and remain conducting, as long as the current through it remains above the holding current level after the initial trigger. This means that while it's not commonly a typical use case of triacs, they can indeed be triggered by DC, provided the triggering signal is sustained.