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Bce0103:Building Science Question Paper
Bce0103:Building Science
Course:Diploma In Civil Engineering
Institution: Meru University Of Science And Technology question papers
Exam Year:2011
QUESTION ONE – (30 MARKS)
(a) (i) Briefly discuss the mechanism of heat propagation in a building structure through:
(i) Conduction
(ii) Convection (2 Marks)
(ii) Calculate ‘U’ value for the flat roof construction in fig 1 shown below comprising
100mm thick concrete slab (r = 0.70), 20mm expanded polystyrene overlay (r = 33.3),
20mm asphalt surfacing (r = 1.0) and internal plaster coat 10mm thick (r = 1.75). Take
the surface resistances Ri = 0.11, Re = 0.04. (3½ Marks)
(iii)State four factors affecting thermal conductivity of a building structure.
(2 Marks)
(b) (i) Explain the following terms in relation to light.
(i) Reflection
(ii) Transmission
20mm asphalt on
20mm polysterene 100mm concrete slab
Fig. 1 10mm plaster
2
(iii)Refraction (1½ Marks)
(ii) Find the number of 60W tungsten filament lamps of efficacy 12.5lm/W for the
following cases:
Room measurements on plan = 15m x 12m
Required illuminance = 150lux
Utilization factor = 0.4
Maintenance factor = 0.80 (3 Marks)
(iii) Define spectrum. How can its existence be shown. (1 Mark)
(iv) Find the intensity of illumination due to direct light at a point 2m from a lamp of 200
Candella. (2 Marks)
(c) (i) Calculate the relative values of sound intensities at distances 4.5m and 8.5m from a
source in air. (2 Marks)
(ii) Describe the mechanism of sound production and the principle of its transmission.
(1½ Marks)
(iii) State three characteristics of sound. (1½ Marks)
(iv) Explain the difference between sound absorption and sound insulation showing how
each can be achieved in a conference room. (2½ Marks)
(d) (i) State ohms law (1½ Marks)
(ii) Find the current carried by a resistor of 200O for an applied p.d. of 240V.
(2 Marks)
(iii) Ignoring heat losses, find the temperature rise of 2 litres of water when heated from
20°?? for 5 minutes by an immersion heater of nominal resistance 600 ohms on 240V
supply.
Take: Specific heat capacity of water = 4200J/Kg°??. 1 Litre of water = 1Kg.
(2½ Marks)
(iv) Determine the resistance of a 500W heating element of 240V. (2 Marks)
SECTION B
QUESTION TWO – (15 MARKS)
(a) A rectangular room 12m x 6m x 4m high has 8m2 of window area. Its walls and ceilings
are of wooden blocks and the flooring is plastered. Calculate the reverberation time for
the room for sound at 500Hz frequency, when it is unfurnished and unoccupied.
Take the sound absorption coefficients at 500Hz as:
- Wood blocks = 0.10
- Plaster = 0.02
- Glass = 0.20
(b) (i) State Stefan’s law of radiation of a perfect black body. (2 Marks)
3
(ii) A total of 0.8Kg of water at 20°?? is placed in a 1.2KW electric kettle. How long a
time is needed to raise the temperature of water to 100°??. (5 Marks)
(Take specific ht capacity of water = 4.2KJ/Kg/°??)
QUESTION THREE – (15 MARKS)
(a) A 100W electric filament lamp with an efficacy of 12.6 lumens per watt is suspended
1.5m above a horizontal bench top. Find the illuminance at
(i) The bench immediately beneath the bench
(ii) The point 1m away on the bench surface. (7 Marks)
(b) (i) Define reverberation time. (2 Marks)
(ii) State two assumptions of Prevost theory of heat exchanges. (2 Marks)
(c) Calculate the Day Light Factor if the outdoor illuminance is 6000lux and the illuminance
at a point inside a room is given as 250lux. (4 Marks)
QUESTION FOUR – (15 MARKS)
(a) Results of an experiment to determine the efficiency of a model electric immersion
heating system are given below:
Mass of water = 100g
Current in heating coil = 1.5A
P.D applied across coil = 3.0V
Initial temp. of water = 24.0°??
Final temp. of water = 29.4°??
Duration of experiment = 10mins
Take specific heat capacity of water = 4200J/Kg°??
Use this information to calculate the efficiency of the coil. (8 Marks)
(b) (i) Using fig.1 above, calculate the rate of heat loss through a flat roof of same
construction materials and thicknesses, measuring 10m x 5m for internal and external
environmental temperatures of 22°?? and 2°??. (5 Marks)
(ii) Define Day Light Factor. (2 Marks)
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