ELV Range

Correct Answer

D — AC voltage < 50 Vrms and DC voltage < 120 V

Concept and Reasoning

The extra-low-voltage range used for safety in building/commercial services is below 50 V rms AC and below 120 V ripple-free DC under the convention used by the question. This paired threshold is given in option D.

Calculation / Key Relation

ELV: AC <50 V rms

DC <120 V

Exam Takeaway

Remember the pair: 50 V AC, 120 V DC.

Common Mistake

Do not use the same numerical limit for AC and DC.