Which statement is true about Triac usage in AC outputs?

Which statement is true about Triac usage in AC outputs?

• A. It is used for DC outputs.
• B. Triac conducts current in either direction when triggered; for AC output modules; cannot be used for DC.
• C. Triac conducts only in one direction; used for DC outputs.
• D. Triac is a diode.

Answer: (B)

A triac acts as a bidirectional switch, which is why it’s suited for AC control. When a gate trigger is received, it starts conducting in both directions, so current can flow through the load during both halves of an AC cycle. This works neatly because AC naturally crosses zero each half-cycle, letting the device turn off automatically as the current drops below the holding level. For DC, there’s no zero-crossing to force the current to drop, so once a triac is turned on it tends to stay on until the circuit current is interrupted, making it unreliable for DC switching. That’s why the true statement describes bidirectional conduction when triggered and its unsuitability for DC. A triac isn’t a diode, and it isn’t limited to one direction; for DC outputs you’d use a different arrangement, such as unidirectional switches like transistors/MOSFETs or a pair of SCRs.

A triac acts as a bidirectional switch, which is why it’s suited for AC control. When a gate trigger is received, it starts conducting in both directions, so current can flow through the load during both halves of an AC cycle. This works neatly because AC naturally crosses zero each half-cycle, letting the device turn off automatically as the current drops below the holding level. For DC, there’s no zero-crossing to force the current to drop, so once a triac is turned on it tends to stay on until the circuit current is interrupted, making it unreliable for DC switching. That’s why the true statement describes bidirectional conduction when triggered and its unsuitability for DC. A triac isn’t a diode, and it isn’t limited to one direction; for DC outputs you’d use a different arrangement, such as unidirectional switches like transistors/MOSFETs or a pair of SCRs.