ASVAB (Armed Services Vocational Aptitude Battery)Electronics Information (EI)Hard
A technician observes that a particular electronic component has a symbol resembling two back-to-back diodes with an additional gate terminal. This component is commonly used for controlling AC power, such as in light dimmers or motor speed controls. What component is this?
- ATriac
- BThyristor (SCR)
- CDiode
- DTransistor
Show answer & explanationAnswer & explanation
Correct answer: A. Triac
The description of two back-to-back diodes with a gate and its application in AC power control (like light dimmers) points directly to a Triac. A Triac is a bidirectional semiconductor device that can conduct current in either direction when triggered, making it ideal for AC control.
Why the other options are wrong
- B. An SCR (Silicon Controlled Rectifier) is a type of thyristor, but it is unidirectional (controls DC or pulsed AC in one direction) and doesn't exactly fit the 'two back-to-back diodes' description as well as a Triac for bidirectional AC control.
- C. A diode allows current in one direction only and doesn't have a gate for control.
- D. A transistor is primarily used for amplification or switching DC, not typically for bidirectional AC power control like a dimmer.
Triac
A three-terminal semiconductor device that can conduct current in either direction when triggered, commonly used for AC power control applications like light dimmers and motor speed controls.
- Bidirectional current flow (controls AC).
- Has a gate terminal for triggering.
- Often seen as two SCRs in inverse parallel.
Memory trick: Triac Twists Two-way Triggering.