Which device is a bidirectional thyristor used for AC power control?

Which device is a bidirectional thyristor used for AC power control?

• A. SCR
• B. DIAC
• C. TRIAC
• D. MOSFET

Answer: (C)

The device that provides bidirectional control of AC power with a single switch is a TRIAC. It’s a thyristor designed to conduct current in either direction between its two main terminals once its gate is triggered. When the gate receives a trigger, the TRIAC latches on and will continue conducting through both halves of the AC waveform until the current falls below its holding level, enabling simple dimming and speed control with one component. An SCR, by contrast, conducts in only one direction, so it can’t handle AC power control with a single device without extra circuitry. A DIAC isn’t a thyristor at all; it’s a triggering device that helps fire a TRIAC (or SCR) rather than performing power switching by itself. A MOSFET is a transistor, not a thyristor, and while it can switch AC in some configurations, it doesn’t provide the natural bidirectional, latching behavior of a TRIAC for AC power control.

The device that provides bidirectional control of AC power with a single switch is a TRIAC. It’s a thyristor designed to conduct current in either direction between its two main terminals once its gate is triggered. When the gate receives a trigger, the TRIAC latches on and will continue conducting through both halves of the AC waveform until the current falls below its holding level, enabling simple dimming and speed control with one component.

An SCR, by contrast, conducts in only one direction, so it can’t handle AC power control with a single device without extra circuitry. A DIAC isn’t a thyristor at all; it’s a triggering device that helps fire a TRIAC (or SCR) rather than performing power switching by itself. A MOSFET is a transistor, not a thyristor, and while it can switch AC in some configurations, it doesn’t provide the natural bidirectional, latching behavior of a TRIAC for AC power control.