Higher Institute of Engineering and Technology
Department of Electrical Engineering
Utilization of Power -3rd Year
SHEET (3)
1.A Room 30 m *15 m is to be illuminated by 15 lamps to give an average illumination of 40
lumen /m2. the utilization factor is 1/4.2 and the depreciation factor is 1.4 .Find The M.S.C.P of
each lamp .
2.A drawing hall 30 m *15 m with a ceiling height of 3.5m is to be provided with a general
illumination of 120 lux .Taking a coefficient of utilization of 0.5 depreciation factor of 1.4
,determine the number of fluorescent tubes required for spacing ,mounting height and total
wattage .take luminous efficiency of fluorescent tube as 40 lumens per watt for 80 watt tube
.space height ratio range from (1-1.5).
3.Estimate the number and wattage of lamps which would be required to illuminate a workshop
space 60 *15 meters by means of lamps mounted 5 m above the working plane . the average
illumination required is about 100 lux , coefficient utilization is 0.4 ,luminous efficiency 16
lumens per watt .Assume space height ratio of unity and candle power depreciation of 1.2 .
4.A reading room 50 m *15m required illumination of 40 meter candle on the reading table
.Assuming space height ratio 1.25 .Calculate
a-The number of lamps required
b- C.P of each lamp assuming the utilization factor as 0.4 ,Maintenance factor as 0.75, efficiency
of each lamp as 0.75 watt per C.P and height of lamp above the reading table as 4 m . Draw a
sketch of arrangement of lamps.
Higher Institute of Engineering and Technology
Department of Electrical Engineering
Utilization of Power -3rd Year
SHEET (3)
5.An illumination of 30 lux is to be provided in classroom 20 *10 m with 40 W fluorescent lamps
.Find the number and layout of the lamps in the lighting installation .Assume a coefficient of
utilization as0.5 , Maintenance factor as .8 and luminous output of 40 w fluorescent lamps as
2400 lumens. Assume S=5m.
6. A building frontage 50 m * 15 m is to be illuminated by flood lighting projectors situated 25 m
away .if the illumination is 100 lux , coefficient of utilization 0.5,depreciation factor 1.5 and
waste light factor 1.2 , Estimate the number and size of projectors .Assume projector wattage
1000 w and efficiency of projector 17 lumen /watt.
