Question

A room of dimensions 10 m × 12 m is to be lighted by 20 lamps of uniform illumination of around 100 lm/m². If the output of each lamp is around 1000 lumens, what will be the utilization factor of the room?
1. 0.4
2. 0.6
3. 0.45
4. 0.5

Answer 1

Correct Answer - Option 2 : 0.6

Given that:

Room dimension = 10 m × 12 m

Output of each lamp (I) = 1000 Lumens

Illumination (E) = 100 lm/m²

Now,

Total lumens emitted by lamps (L_T) = Number of lamps × output of each lamp

∴ L_T = 20 × 1000

L_T = 20000 lumens

Lumens received by working area (L_r) = Area of space × illumination

∴ L_r = 10 m × 12 m × 100 lm/m²

L_r = 12000 lumens

Now,

Utilization factor \( = \frac{{{L_r}}}{{{L_T}}}\) 

Where,

L_r = lumen received by working plane

L_T = Lumen emitted by lamps

∴ utilization factor \( = \frac{{12000}}{{20000}}\) 

Utilization factor = 0.6