Energy Engineering MCQs and Answers (FREE)

1: A stone that weighs 70 kg in air, weighs 120 kg when immersed in water. What is the specif‌ic weight of the stone?

A. 2200 kg/m3

B. 2400 kg/m3

C. 2620 kg/m3

D. 2840 kg/m3

2:

The work ratio of a gas turbine plant working on a Joule cycle is 45%. If it produces 5000 kW of power, what is the power consumed by the compressor?

A.

4512.8 kW

B.

5081.3 kW

C.

6111.11 kW

D.

8304.5 kW

3: If the work produced by a Carnot engine operating between 350 °C and 30 °C is 400 kJ, then f‌ind the entropy change during heat addition.

A. 0.8

B. 1.03

C. 1.25

D. 1.67

4: What will be the discharge over a 5-meter long suppressed rectangular weir with head over crest = 0.4 m?

A. 2.3 m3/s

B. 1.98 m3/s

C. 2-5 m3/s

D. 3.1 m3/s

5: A laminated wall of surface area 1.5 m2, is made up of 0.3 m of refractory bricks (k = 2 kcal-m/hr m2 °C), 0.3 m of insulation (k =0.15 kcal-m/hr m7- °C)and 0.45 m of brick (k = 1.5 kcal-m/hr m7- °C). If the inner and outer temperature of the wall is 1030°C and 30°C. respectively. what is the rate of heat transfer?

A. 546.65 kcal/hr

B. 587.32 kcal/hr

C. 612.24 kcal/hr

D. 643.16 kcal/hr

6: A MOSFET operates in which of the following modes when VGSGS(TH)?

A. hmic mode

B. Saturation mode

C. Active mode

D. Cut-off mode

7: Which of the following expressions calculates the overland flow time (To in hours) for any basin? Where, L0 = distance of critical point and H = difference in elevation.

A. a)

B. b)

C. C)

D. d)

8:

For a generic heat exchanger. with two ends (A and b)at which the hot and cold streams enter or exit on either side. which of the following options represent the Log Mean Temperature Difference? (Assume.

ATA is the temperature difference between the two streams at end A; ATB is the temperature difference between the two streams at end B.)

A.

a)

B.

b)

C.

C)

D.

d)

9: Which of the following cycles works as a reverse of Bell-Coleman air refrigeration cycle?

A. Ericsson cycle

B. Brayton cycle

C. Otto cycle

D. Rankine cycle

10: What is the order of the mass flow ratio of Freon-12 in comparison to NH3 if the temperature limits and refrigeration load are the same?

A. 1:5

B. 5:1

C. 1:9

D. 9:1

11: The presence of which of the following gases is tested by doing the lead acetate test?

A. CO

B. C02

C. CH 4

D. H2S

12:

Given.

L = length of overland flow (in km) from the critical point to the mouth of a drain

H = total fall of level

Using which of the following expressions will you calculate the time of concentration (Ti)?

A.

a)

B.

b)

C.

c)

D.

d)

13: Composition of landfill gases is primarily:

A. co and N02

B. co2 and N02

C. so2 and co

D. CH4 and co2

14:

To calculate the velocity of flow in a circular sewer of diameter 'D' (running full) using Chezy's formula {V=C «/ (rs)], what should be the value of hydraulic mean radius (where. r= hydraulic mean depth of flow and S: hydraulic gradient)?

A. D/2

B. D/4

C. D/6

D. D/8

15:

Given,

n = rugosity coeff‌icient,

r = hydraulic depth and.

s = bed slope of sewer

The formula ("V=1/n r288”) for determining the velocity of flow in m/s was evolved by which of the following?

A.

Kuichling

B.

Fruhling

C.

Chezy

D.

Manning

16:

The settlement velocity of the particles is calculated using Hazin‘s formula,

VS = 418(GS-Gw)d[3T+7O/100 ] (where symbols have their usual meaning). when the particle diameter is:

A.

less than 0.02 mm

B.

greater than 0.01 mm

C.

less than 0.1 mm

D.

more than 0.1 mm

17: Find the ratio of the temperature drop across two layers of a composite wall of a furnace, where the two layers have equal thickness and the ratio of thermal conductivities is 4:5.

A. ⅓

B. 114

C. 3/4

D. 5/4

18: Twenty-f‌ive percent of the absorbed heat from the source is rejected by an engine working on Carnot cycle. If the sink temperature is maintained at 30°C, calculate the value of source temperature.

A. 800°C

B. 695°C

C. 1485°C

D. 1032°C

19: Find the effective head under which a Francis turbine operates. It works at 450 rpm, has a unit speed of 60 rpm and develops a power of 550 kW.

A. 104 m

B. 83.7 m

C. 62.5 m

D. 51.9 m

20:

If. T9 is generator temperature, T8 is evaporator temperature and Ta is environmental temperature; then which of the following gives the theoretical maximum COP of a vapour absorption system?

A.

a)

B.

b)

C.

c)

D.

d)

21:

What is the compactness coefficient of a drainage basin with perimeter P and area A?

A.

a)

B.

b)

C.

C)

D.

d)

22:

Forty percent of the heat supplied is rejected by a reversible heat engine during a cycle of operation.

What will be the COP if this engine is reversed and used as a heat pump?

A.

1.8

B.

2.3

C.

2.5

D.

2.9

23:

The ratio between the high and the low working temperatures of a refrigerator based on reversed Carnot Cycle is 0.6. If a heat pump is operated between this same temperature range.

what will be the COP of the heat pump?

A.

5

B.

4.3

C.

3.6

D.

2.5

24: 1200 kl of heat is transferred from a constant temperature system at 700 K to another at 500K (environmental temperature = 300 K). Calculate the loss of available energy associated with this transfer.

A. 360 kJ

B. 396.6 kJ

C. 458.7 kJ

D. 480 kJ

25:

In the given image. which of the following curves is applicable when the thermal conductivity of a material increases with increase in temperature?

A.

A

B.

B

C.

C

D.

D

26:

What is the expression for the maximum blade eff‌iciency of a Parson's turbine? Where, a = jet angle at the entrance.

A. Cos2a/(1- Cos2a)

B. (2 Cos2a)/( 1+ Cos2a)

C. Cosu/2

D. C0520

27: What will be the cycle eff‌iciency for the maximum work capacity in a gas turbine operating on Brayton cycle? It is given that the Brayton cycle has maximum temperature of 1250 K and minimum temperature of 350K.

A. 35%

B. 43%

C. 47%

D. 51%

28: What is the range of typical density in kg/cm (in-situ) of well-compacted municipal solid waste in a landf‌ill?

A. 150 to 320

B. 310 to 500

C. 600 to 770

D. 850 to 1200

29: Determine the value of the COP of a vapour compression refrigeration system. Given, enthalpy at beginning of compression = 80 kJ/kg. enthalpy at the end of compression = 180 kJ/kg and enthalpy at the end of condensation = 230 kJ/kg.

A. 1.2

B. 1.5

C. 2.3

D. 3.6

30:

What is the area of cross-section of a standard egg shaped-sewer. where diameter of the upper circular portion is D?

A.

a)

B.

b)

C.

C)

D.

d)

31: I Find the blade-speed ratio for maximum diaphragm efficiency in a simple impulse turbine. It is given that the nozzle angle at the entrance is 35°.

A. 0.41

B. 0.56

C. 0.62

D. 0.83

32: For a circular sewer (with diameter d) and a square section sewer (of side a) to be hydraulically equivalent. which of the following needs to be true?

A. nD8/3 ___ 4a8/3

B. 1-D5/3 = 4a5/3

C. nD8/3 : 4a5/3

D. nD3/5 = 4a8/3

33:

A circular tank of diameter d and water depth H receives sewage 0 per hour. The detention time of the tank is:

A.

a)

B.

b)

C.

c)

D.

d)

34: What is ratio of the lower to the higher absolute temperatures for a Carnot refrigerator that has a COP = 7?

A. ⅗

B. 5/9

C. ⅞

D. 4/7

35:

Fill in the blank.

The value of B for a power BJT with IC =18 A. la = 2.2 A and 'cs =14 mA is .

A.

7.63

B.

8.12

C.

8.73

D.

9.34

36: If 0 = maximum flood discharge, C = Ryves coeff‌icient and A = catchment area then Q is equal to:

A. CA ⅓

B. CA ⅕

C. CA ⅔

D. CA 2/5

37: What will be the value of relative humidity when wet bulb depression is zero?

A. 0

B. 30%

C. 80%

D. 100%

38: Assuming the energy released by coal as 92OX107 kJ/h, calculate the rate at which heat is rejected from a thermal electric power plant, which produces 1200 MW of power.

A. 530.2 MW

B. 780.9 MW

C. 1100.3 MW

D. 1355.5 MW

39: In a stainless f‌in (thermal conductivity = 0.18 W/cm°C)of a constant cross-sectional area of 2.5 cm2 and length 1 cm exposed to ambient temperature of 50°C (with a surface heat transfer co-eff‌icient of 0.003W/cm2°C). the temperature distribution is given by (T - T...) = 3x2 - 5x + 6. where T is in °C and x is in cm. Find heat dissipated by the f‌in surface for a base temperature 120°C.

A. 3.67 w

B. 4.28 w

C. 4.83 w

D. 5.14 w

40: 300 KJ/s of heat is supplied to a heat engine at a constant fixed temperature of 230°C. If heat is rejected at 30°C then assuming the cycle as reversible, calculate the amount of heat rejected.

A. 180.71 KJ/s

B. 203.4 KJ/s

C. 229.5 KJ/s

D. 253.5 KJ/s

41: A sharp edged vertical orif‌ice issues a jet of water under a constant head of 0.55 m. The horizontal and vertical co-ordinates measured from the vena-contracta. at a certain point of issuing jet. are 0.512m and 0.09m, respectively. Assuming Cd = 0.7, find the value of CC.

A. 0.48

B. 0.53

C. 0.6

D. 0.71

42:

Given. 5 = potential inf‌iltration and p = rainfall (in centimetre) in a drainage of a soil with fair pasture cover. The direct runoff Q can be calculated by using which of the following expressions?

A.

a)

B.

b)

C.

c)

D.

d)

43: Calculate the degree of reaction in a reaction turbine, if the enthalpy drop in a stage is 70 units and the enthalpy drop in the moving blades is 40 units.

A. 0.57

B. 0.73

C. 0.92

D. 1.06

44: The cycle direction of a Carnot engine (with an eff‌iciency of 60%) is reversed. what is the COP of reversed Carnot cycle?

A. 0.53

B. 0.66

C. 0.82

D. 0.97

45: A gas turbine is supplied with gas at 1200 K and 10 bar to expand adiabatically to 2 bar. Find the power developed in kW/kg of gas per second and the exhaust gas temperature. Mean specif‌ic heat at constant pressure is 1.0425 kJ/kgK and mean specific heat at constant volume is 0.7662 kJ/kgK.

A. 876 kW/kg and 984 K. respectively

B. 672 kW/kg and 732 K. respectively

C. 434 kW/kg and 784 K, respectively

D. 381 kW/kg and 539 K. respectively

46:

k = soil permeability (assuming the soil to be homogeneous and isotropic)

Where, H1 and H2 = depths of two wells at distances r, and r2, respectively, from the main well
How is the yield of wells determined according to Thiem's formula?

Q = discharge

A.

a)

B.

b)

C.

C)

D.

d)

47:

The emissivities of two inf‌inite parallel planes are 51 and 52. respectively. What is the interchange factor for radiation from surface 1 to 2?

A.

a)

B.

b)

C.

C)

D.

d)

48: A 250 mm pipe line has a pitot-static tube paced in its centre, with one orif‌ice pointing upstream and the other perpendicular to it. Assuming the pressure difference between the two orifices to be 50 mm of water when discharge through the pipe is 1500 L/min and the mean velocity in the pipe to be 0.83 of the central velocity, find the coeff‌icient of the pitot tube.

A. 0.62

B. 0.67

C. 0.78

D. 0.83

49:

Given below is the information regarding a steam power plant.

Power developed by the turbine = 1300 kW

Heat supplied to the boiler = 3400 kJ/kg

Heat rejected by the system to cooling water = 2500 kJ/kg

Teed pump work required to condensate back into the boiler = 7kW

What will be the mass flow rate through the cycle?

A.

0.85 kg/s

B.

1.4 kg/s

C.

2.9 kg/s

D.

3.6 kg/s

50: From which of the following chemical compounds is the odour of drying paint or varnish is derived?

A. Ethylene

B. Ethene

C. Methane

D. Benzene

51: Water f‌lows through a horizontal column of sand, which is 0.5 m long and 80 mm in diameter. If the discharge is 5.6 L/min and the pressure drop across the column of sand is 22.5 kPa. determine the value of transmission constant.

A. 4.05 mm/s

B. 5.4 mm/s

C. 7.2 mm/s

D. 3.68 mm/s

52:

If VS = settling velocity. d = diameter of a particle. Cd = coeff‌icient of drag. G = specific gravity of the

particle, then according to Stokes' law, f‌ind the settling velocity of spherical particles of size less than 0.1mm in water.

A.

a)

B.

b)

C.

c)

D.

d)

53:

Fill in the blank.The time interval from the instant when the current through an outgoing thyristor becomes zero to the instant when a positive voltage is reapplied is called .

A.

overlap angle of a rectifier

B.

extinction angle of a rectifier

C.

firing angle of a rectif‌ier

D.

none of the above

54: Calculate the peripheral velocity of a Pelton wheel, whose speed ratio while operating under a head of 950 m is 0.4.

A. 51.3

B. 54.6

C. 60.8

D. 65.5

55: A pipe of diameter 0.2 m is to be f‌itted with a venturi meter, where the pressure head of the flowing liquid is 7.2 m and the maximum flow is 6 m3/min. What is the least diameter of the throat to make sure that the pressure head does not become negative? (Consider K = 0.96)

A. 103.4 mm

B. 135.6 mm

C. 121 mm

D. 143.8 mm

56: Sewage is unloaded at the point of treatment through which of the following types of sewer systems?

A. Lateral sewer

B. lntercepting sewer

C. Outfall sewer

D. Main sewer

57:

If the heat flow equation through a cylinder of inner radius r, and outer radius r2 is desired in the same form as that for heat flow through a plane wall. then which of the following will give the equivalent area Am?

A.

a)

B.

b)

C.

C)

D.

d)

58: If a 5 KW, 25 litre water heater is switched on for 15 minutes and all the electrical energy goes into the heating of water, then what is the increase in temperature of water? (Take Cp of water = 4 KJ/Kg K.)

A. 28°C

B. 33°C

C. 40°C

D. 45°C

59: Calculate the total losses in the strainer and bends in a pipe, if h = loss due to friction in a pipe.

A. 0.15 h

B. 0.25 h

C. 0.33 h

D. 0.42 h

60: Two Carnot engines connected in a series combination operate between the temperatures of 200°C and 40°C. Assume that the engines produce equal amount of work and f‌ind the intermediate temperature.

A. 85°C

B. 92°C

C. 107°C

D. 120°C

61:

Which of the following options give the NTU of a heat exchanger with heat transfer surface area = A and overall heat transfer coefficient = U, considering it is handling two fluids of heat capacities. C1 and C2 such that C1> C2?

A.

AU/C2

B.

AU/c,c2

C.

eC1-C2

D.

eC2-C1

62: Determine the forward current in a p-n junction diode (having a reverse saturation current rating of 55 nA at 32°C) for a forward voltage drop of 0.52 V. (Take, VT at 32°C =26 mV.)

A. 14.76 A

B. 23.19 A

C. 26.68 A

D. 28.53 A

63: Which of the following statements is correct?

A. Forward break over voltage of a thyristor decreases with increase in the gate current

B. Reverse breakdown voltage of a thyristor is dependent on the gate current

C. Reverse saturation current of a thyristor decreases with the gate current

D. In the pulsed gate current triggering of a thyristor the gate current pulse width should be less than the Turn-On time of the device

64: Which of the following components of power dissipation in a Power Semiconductor device is reduced by an RCD Switching-Aid-Network?

A. Turn-Off losses

B. Turn-On losses

C. Total switching losses

D. On-state losses

65: What will be the gauge pressure inside a rain drop of 2 mm diameter if the surface tension of watervair interface is 0.08 N/m?

A. 137 N/rn2

B. 160 N/m2

C. 183 N/m2

D. 196 um2

66:

Given,

n = rugosity coeff‌icient.

r = hydraulic depth and,

s = bed slope of sewer

A refrigerator of COP 6 is driven by a heat engine (of eff‌iciency = 40%). For each MW of heat removed in the refrigerator, what will be the net heat input to the engine?

A.

416.67 kJ

B.

482.74 kJ

C.

541.38 k]

D.

666.67 kJ

67:

Fill in the blank.

The head lost due to friction. in a pipe flow. is 8 m. For maximum power transmission through a pipe.

the total head at the inlet of the pipe has to be maintained at.

A.

18 m

B.

24 m

C.

40 m

D.

32 m

68: The volume of a liquid decreases by 0.2% if the pressure of the liquid is increased from 80 kg(f)/cm2 to 150 kg(f)/cm2. Calculate the bulk modulus of elasticity of the liquid.

A. 4.4 x104 kg(f)/cm2

B. 3.5 x104 kg(f)/cm2

C. 7.6 x104 kgm/cm2

D. 5.9 x104 kg(f)/cm2

69: A hall has Room Sensible Heat (RSH) = 60kW and Room Latent Heat (RHL) = 40kW. Assuming, there are no other sources of heat addition or leakage except the air conditioner, f‌ind the value of Room sensible heat factor (RSHF).

A. 0.4

B. 0.5

C. 0.6

D. 0.7

70: For the same velocity and pressure drop, the equivalent diameter of a circular duct corresponding to a rectangular duct that has longer side "I" and shorter side "w" is:

A. 2(1 + w)/l

B. 20 + w)/w

C. Lw/2(l + w)

D. 2lw/(l +w)

71: Calculate the percentage decrease in the volume of sludge when the moisture content of sludge in a sludge digestion tank is reduced from 80% to 60%.

A. 30%

B. 40%

C. 50%

D. 60%

72: For controlling gas and leachate moments, which material should be used as landf‌ill salient?

A. Butyl rubber

B. Soda ash

C. Fly ash

D. Sand

73:

Given below is the one-dimensional temperature distribution of a large concrete slab, which is1 m thick.

T = 5-12x+22x2+ 12x3 (T = temperature and x = distance from one face of the wall towards the other face)

Find the rate of change of temperature at the other face of the wall if the slab material has a thermal diffusivity of 2x10’3 m2/hr.

A.

0.11°C/h

B.

0.23°C/h

C.

0.38°C/h

D.

0.44°C/h

74: A water turbine that does NOT require a draft tube is called a:

A. pelton turbine

B. straflo turbine

C. bulb turbine

D. francis turbine

75: A single-phase full-wave rectif‌ier has an output voltage form factor of:

A. 211

B. n/2v2

C. m2

D. n

76:

Match the items from List-1 (Semiconductor device) with the items from List-2 (Characteristics) and select the answer with the correct combination of items.

A.

A-3, B-2, C-1, 0-4

B.

A-2, B-3, C-1, 0-4

C.

A-3. B-2. 04, 0.1

D.

A-2, B-3, C-1, 0-4

77: At what temperature, do centigrade and Fahrenheit scales have same reading?

A. -27

B. -40

C. -80

D. -273

78: The diameter of a small sphere is 4 mm and its specif‌ic gravity is 2.7. If the sphere falls 0.5 m in 20 5 through a liquid whose specific gravity is 0.9, what is the absolute viscosity of the liquid?

A. 0.044 poise

B. 0.052 poise

C. 0.062 poise

D. 0.81 poise

79:

The wavelength of a radiation emitted by the Sun's surface at 6000°C is 0.6 u. The wavelength of radiation emitted by a furnace at 350°C (through a small opening) is:

A. 4.7 p

B. 5.1 p

C. 5.6 p

D. 6 u

80: Which of the following factors affect the time of overland f‌low?

A. Interception

B. Duration of rainfall

C. Slope of the basin

D. Time of concentration

81: Although hydroelectric dams generate electricity without producing greenhouse gases, they ________.

A. Tsunami

B. Eliminate

C. Ethanol

D. Europe

E. Biomass

82: Coal forms from that accumulates in a(n) depositional environment.

A. Plant material; reducing

B. Lignite;bituminous;anthracite

C. High permeability and porosity

83: A ________ detects the speed that a given device can handle and communicates with it at that speed.

A. Port

B. Switch

C. Codec

D. Modem

84: ________ are small-scale winds produced by a locally generated pressure gradient.

A. Trade winds

B. Air pressure

C. Subtropical high

D. Local winds

85: Aristotle first proposed that _____ was at the center of the solar system.

A. The sun

B. Earth

C. The moon

D. Jupite

Energy Engineering MCQs

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