EE 365 ELECTRICAL SERVICES DESIGNSAMPLE EXAMINATION QUESTIONS

NOVEMBER 20101. Which of the following is the frequency of the extreme visible violet end of light spectrum.a) 7.5 HZ b) 5.5 HZ c) 4.5 HZ d) 3.5 HZ

A metal filament gas filled lamps takes 0.42 A from a 230 V supply and emits 1120 lm. Use the above information for questions 2 and 3 2. Calculate the mean spherical candle power (MSCP) of the lamp a) 80.2 cd b) 90.5 cd c) 89.13 cd d) 102,45 cd3. Calculate the mean spherical candle power (MSCP) per watt of the lamp a) 0.923 cd /W b) 0.876 cd /W c) 0.654 cd /W d) 0.435 cd /W Four lamps are used to illuminate a certain room .The luminous efficacy of each lamp is 13 lm / W and the lamps have a total of 10000 lumens. Use the above information for questions 4 and 5 4. Calculate the MSCP per lamp a) 198.94cd b) 207.76 cd /W c) 305.65 cd d) 250.43 cd 5. Calculate the cost of energy consumed in 4hrs if the charge for electrical energy is 52 Pesewas / kWh a) GH2.30 b) GH1.60 c) GH3.00 d) GH2.25 A filament lamp is enclosed in a fitting that absorbs 20 percent of the light flux from the lamp and distributes the remainder uniformly over the lower hemisphere. The lamps may be assumed to have luminous efficacy of 15 lm / W. The fitting is suspended 2m above the centre of a horizontal surface 3m square. No point on the horizontal surface is to have an illuminance less than 20 lux. Reflected light from other surfaces may be neglected. Use the above information for questions 6 - 8 6. Determine the necessary luminous intensity of the light from the lamp in the lower hemisphere.a) 383.14cd b) 247.73 cd /W c) 305.26 cd d) 262.13 cd 7. Determine the total light flux radiated from the lamp on the lower hemisphere. a) 1800.38 lumens b) 1423.56 lumens c) 1945.67 lumens d) 2056.03 lumens 8. Determine the necessary rating (in watts) of the lamp a) 180 .45W b) 200.67 W c) 150.78 W d) 129.71W A 15m by 25m hall is lit by fluorescent lamps. The height of the ceiling is 4m. The width of the hall is 15m. The ceiling is painted white and the wall is painted medium hue..Assuming the cleaning of the ceiling, the walls and the luminaries is done every two years and the soiling rate. is normal. Under this condition determine the number of 40 W fluorescent lamps required for the hall. Assume that the luminaries hang 20 cm below the ceiling and the working plane 80cm above the floor. From luminaires data, the selected lamp produces a luminous flux 2800 lumens and the illumination level requirement for the hall is 250 luxUse the above information to answer questions 9 - 119. Determine the room index of the hall a) 1.78 b) 4.50 c) 2.36 d) 3.13 10. Determine the utilization factor of the lamps a) 0.650 b) 0.420 c) 0.490 d) 0.509 11 Determine the number of twin fluorescent lamps required for the hall. a) 72.0 b) 53.0 c) 67.0 d) 84.0.

A typical lecture hall is 40 metres long and 15 metres wide with a ceiling height. of 4 metres above the work plane which in turn is 0.86 metre above the floor level . The ceiling reflectance is 80%, walls reflectance is 30%, and floor reflectance is 20%. Determine the number of 40W fluorescent fixtures required for the effective illumination of the hall .Assume a the average luminous flux of a fluorescent is 2800 lumens and illumination requirement of the hall is 250 lux and maintenance factor of 0.8 Use the above information to answer questions 12 - 1512. Calculate the effective ceiling reflectance of the lecture hall if fluorescent fittings are to be used for the hall.a) 60% b) 80% c) 50% d) 0% 13 Determine the effective floor reflectance of the hall.a) 16.70% b) 14.80% c) 18.55% d) 19.20% 14. Determine the utilization factor of the lamps a) 0.685 b) 0.573 c) 0.845 d) 0.735 15. Determine the number of twin fluorescent lamps required for the hall.a) 53 b) 42 c) 56 d) 49

A 240V, 4kW fixed resistive load is to be fed by a PVC insulated and sheathed cable. The insulation condition involves the cable being run with four other similar cables . The ambient temperature is assessed as 40oC. Protection is by a semi enclosed fuse. The length of run is 20m. Use the above information to answer question 16 and 17

16. Calculate the size of cable required to serve the resistive load.a) 10mm2b) 25mm2c)16mm2d)6mm2

17. Determine the size of cable required to serve the resistive load if the protection is by a MCB. a) 16mm2b) 4.0 mm2c) 2.5mm2d) 6.0mm2

18. Calculate the number of discharge lamps of rating 80W that can be controlled by a 5A switch.a)8 b) 6 c)4d) 2

19 Calculate the number of 40 W fluorescent lamps that can be connected in a 5A, 240V circuit if two 80W incandescent lamps must used.a)13 b) 14c)15d)11

20 Calculate the number of 80W fluorescent lamps that can be connected to a 5A switch.a) 8 b) 6c)4d)2

21 A combination of 4ft fluorescent and incandescent lamps are to be connected to a 5A switch. The ratings of the 4ft fluorescent and incandescent lamps are 80W and 100W respectively if 2 incandescent lamps are used, how many fluorescent lamps can be added?a) 5 b) 3c)6d)7

In a building services design for a four-bedroom guest house, the following circuits were obtained. A. Lighting circuits-10B. Air conditioner circuits - 9C. Cooker circuits- 6D. 13A socket outlets - 8 i) 5A fuse is used for lighting circuits, ii) 20A fuse is used for air conditioners, iii) 30A fuse for socket outlets and iv) 6kW cooker appliance is protected by a 30A fuse. The Ambient operating temperature is 40 oC. Use the above information to answer questions 22 - 2522. Calculate the total expected current to be drawn from the main switch by the lighting circuits.a) 30A b) 35.2A c) 37.5A d) 40.8A

23 Determine the current that can be drawn by the cookers from the main switch at any given time.a) 130A b) 105A c) 150Ad) 175A

24 Determine the minimum current that can be drawn by the socket outlet circuits from the main switch.a)120A b) 108A c) 135A d) 115A25 Determine the current that can be drawn by the air conditioners from the main switch.a) 135A b) 125A c) 100A d) 110A26 Determine the size of the PVC cable of length of 10 metres that can be used to supply a cooker unit.a) 6mm2 b) 10mm2 c)16mm2 d) 4mm227 If 3 lighting circuits, 2 air conditioner circuits and 2 socket outlet circuits are to be connected to one distribution board calculate the size of the three phase PVC cable of length of 20 metres that should be used to supply the distribution board.a) 6mm2 b) 10mm2 c)16mm2 d) 4mm2 A drawing hall 30 metres by 13 metres with a ceiling height of 3 metres above the floor is to be provided with a general illumination of 120 lux. Taking U.F. of 0.5 and M.F. of 1.4 and assuming the luminous efficacy of the tube as 40 lumens / watt for 80W tube, Use the above information to answer questions 28 - 3128 Determine the number of 80 watts tubes required for the hall.a) 58 b) 41 c) 38 d) 2829 If the lamps are arranged with 7 twin lamps along the length and 3-twin lamps along the width, calculate the space to mounting height ratio along the length.a) 3.35/3 b) 4.0 /3 c) 5.0/3 d) 3.0/330. Using the information in question 29, find the space to mounting height ratio along the width.a) 3.35/3 b) 4.7 /3 c) 5.0/3 d) 3.9/331 A room 20m 10m is to be illuminated by eight lamps and the average illumination is to be 50 lumens /m2. If U.F. = 0.48 and M.F. = 1.2 calculate the mean spherical candle power of a lamp.a) 448 b) 348 c) 248d) 148

EMMANUEL ADDO1