How is the efficiency of instrument calculated?

Question

Question

This question was previously asked in

PGCIL DT Electrical 12 March 2022 (NR II) Official Paper

Answer 1

The correct answer is option 4):

Concept:

The efficiency of instruments is the ratio of voltage and current rating to the power rating.

For an ammeter, the current rating is considered and for a voltmeter, the voltage rating is considered

Power taken by the is given by

For Ammeter: P = I²R

For Voltmeter: P =