Determine the number of lamps required to illuminate a room of area 200 m² to a level of 310 lx. Assume utilisation factor = 0.6, maintenance factor = 0.63 and the lumen output of each lamp = 2850 lm.

Question

Question

This question was previously asked in

MPPGCL JE Electrical 19 March 2019 Shift 2 Official Paper

Answer 1

Concept

The number of lamps required to illuminate a room is given by:

\(N={E\times A\over F\times UF\times MF}\)

where, N = Number of lamps

E = Illuminance level (lux)

A = Area

F = Luminous flux per lamp (lm)

UF = Utilisation factor

MF = Maintenance factor

Calculation

Given, E = 300 lux

A = 200 m2

F = 2850 lm

UF = 0.6

MF = 0.63

\(N={310\times 200\over 2850\times 0.6\times 0.63}\)

N = 57.5 ≈ 58