GATE 2026 AR — Architecture – Question 64

Building Services · Principles of electrification and illumination and special lighting for buildings · 2 marks · Numerical answer

A 25×12 m conference room has CFL efficacy 60 lumen/W and lighting-power density 12 W/m². Utilisation factor is 0.8 and maintenance factor 0.5. Find average illumination in lux, as an integer.

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Correct answer: 288 to 288

Explanation

Installed power is area×LPD=300×12=3600 W. Lamp flux is 3600×60=216000 lumens. Maintained useful flux is 216000×0.8×0.5=86400 lumens. Divide by 300 m² to get 288 lux. Equivalently, efficacy×LPD×utilisation×maintenance gives the same result directly.

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