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SarkariResultOutAdditional Assistant Engineer (Electrical) · 2026

Previous Year Question

In which application would you select a TRIAC over a regular SCR?
  1. For switching a DC relay coil.
  2. For amplifying a small input signal.
  3. For rectifying DC voltage in a power supply.
  4. For controlling bidirectional AC power to a lamp.

Correct answer: D

Explanation

A TRIAC can conduct in both directions and is therefore well suited to phase control of AC loads such as lamps, heaters and small motors. A conventional SCR is unidirectional.

Step-by-step solution

Bidirectional AC Switching explanatory diagram

Correct Answer

D — For controlling bidirectional AC power to a lamp.

Explanation

A TRIAC can conduct in both directions and is therefore well suited to phase control of AC loads such as lamps, heaters and small motors. A conventional SCR is unidirectional.

Key Concept

Bidirectional AC Switching

Exam Point

TRIAC = bidirectional AC switch.

Exam tip

TRIAC = bidirectional AC switch.

Quick method

TRIAC = bidirectional AC switch.