Correct AnswerB. Silicon-controlled rectifier
Quick Explanation
An SCR is semi-controlled because its gate controls turn-on, but the gate cannot normally force it off. Once latched, an SCR turns off only when anode current falls below the holding current or reverse voltage/commutation is applied.
Detailed Explanation
Correct Answer
B — Silicon-controlled rectifier
Concept and Reasoning
An SCR is semi-controlled because its gate controls turn-on, but the gate cannot normally force it off. Once latched, an SCR turns off only when anode current falls below the holding current or reverse voltage/commutation is applied.
Calculation / Key Relation
SCR: gate-controlled turn-on
turn-off by current extinction/commutation
Exam Takeaway
Semi-controlled means control over turn-on but not normal gate turn-off.
Common Mistake
Do not group fully gate-controlled devices such as MOSFET/IGBT with the SCR.
