RRB JE MIXED QUESTIONS 2
1. In which of the following mechanisms , is heat conducted in liquid and gas
(a) Lattice vibration
(b) Transportation of free electrons
(c) Collisions and diffusion
(d) No heat conducted
Answer: C
2. An essential requirement for the transfer of heat from one body to another body is that
(a) Both bodies must be solids
(b) Both bodies must be in contact
(c) Temperatures of the two bodies must be different
(d) Temperatures of the two bodies must be same
Answer: C
3. Heat is transferred by conduction , convection and radiation in
(a) Insulated pipe carrying hot water
(b) Refrigerator freezer coils
(c) Melting of ice
(d) Boiler furnaces
Answer: D
4. The concept of overall heat transfer is used in the heat transfer in the case of
(a) Conduction
(b) Convection
(c) Radiation
(d) Combined mode of heat transfer of conduction and convection
Answer: D
5. The unit of thermal conductivity in S.I. unit is
(a) W/mK
(b) Wยฒ/mK
(c) W/mยฒK
(d) W/m
Answer: A
6. Fourier’s law of heat conduction gives the heat flow for
(a) Irregular surfaces
(b) Non – uniform temperature surfaces
(c) One dimensional cases only
(d) Two dimensional cases only
Answer: C
7. Metals are good conductor of heat because
(a) Their atoms collide frequently
(b) Their atoms are relatively far apart
(c) They contain free electron
(d) They have high density
ย Answer: C
8. Heat conduction in gases is due to
(a) Electromagnetic waves
(b) Motion of electrons
(c) Mixing motion of the different layers of the gas
(d) Elastic impact of molecules
Answer: D
9. The heat flow through solids only by
(a) Conduction
(b) Convection
(c) Radiation
(d) Does not flow
Answer: A
10. Heat transfer by molecular collision in
(a) Conduction
(b) Convection
(c) Radiation
(d) Scattering
Answer: A
11. Which one of the following have a highest thermal conductivity?
(a) Boiling water
(b) Steam
(c) Solid ice
(d) Rain water
Answer: C
12. Heat pipe is widely used now a days , because
(a) It acts as an insulator
(b) It acts as conductor and insulator
(c) It acts as a superconductor
(d) It acts as a fin
Answer: C
13. In which one of the following materials is the heat propagation minimum due to conduction heat transfer?
(a) Lead
(b) Copper
(c) Water
(d) Air
Answer: D
14. Heat transfer takes place according to
(a) Zeroth Law of Thermodynamics
(b) First Law of Thermodynamics
(c) Second Law of Thermodynamics
(d) Third Law of Thermodynamics
Answer: C
15. Which of the following is not a method of heat transfer?
(a) Conduction
(b) Convection
(c) Condensation
(d) Radiation
Answer: C
16. According to kinetic theory of heat
(a) Temperature should rise during boiling
(b) Temperature should fall during freezing
(c) At low temperature all bodies are in solid state
(d) At absolute zero there is absolutely no vibration of molecules
Answer: D
17. Which of the following is the worst conductor of heat in the group?
(a) Air
(b) Plastic
(c) Vaccum
(d) Aluminium
Answer: C
18. Units for thermal conductivity
(a) J/kg.K
(b) J/mol.K
(c) J/sec.Kยฒ
(d) W/m.K
Answer: D
19. In which one of the following materials , is the heat & energy propagation minimum due to conduction heat transfer?
(a) Lead
(b) Copper
(c) Water
(d) Air
Answer: D
20. The bending of bimetallic strips during rise in temperature is due to difference in their :
(a) Coefficient of linear expansion
(b) Thickness
(c) Thermal conductivities
(d) Elastic properties
Answer: A
21. Air can be best heated by steam in a heat exchanger of
(a) Plate type
(b) Double pipe tyre with fins on steam side
(c) Double pipe tyre with fins on air side
(d) Shell and tube type
Answer: C
22. The thermal diffusivity of a substance is given by
[Where , k = Thermal conductivity ; ฯ = Mass density ; cp = specific heat]
(a) kฯ/cp
(b) k/ฯcp
(c) kcp/ฯ
(d) ฯcp/k
Answer: B
23. Heat is mainly transferred by conduction , convection and radiation in
(a) Insulated pipes carrying hot water
(b) Refrigerator freezer coil
(c) Boiler furnaces
(d) Condensation of steam in a condenser
Answer: C
24. Heat transfer in liquids and gases is essential due to
(a) Conduction
(b) Convection
(c) Radiation
(d) Conduction and Radiation put together
Answer: B
25. Fins are provided on heat transferring surface in order to increase :
(a) Heat transfer area
(b) Heat transfer coefficient
(c) Temperature gradient
(d) Convection and Radiation
Answer: A
26. The effectiveness of a fin will be maximum in an environment with
(a) Free convection
(b) Forced convection
(c) Radiation
(d) Convection and Radiation
Answer: A
27. The effectiveness of a fin will be maximum in an environment with
(a) Free convection
(b) Forced convection
(c) Radiation
(d) Convection and Radiation
Answer: A
28. Fins are made as thin as possible to
(a) Reduce the total weight
(b) Accommodate more number of fins
(c) Increase the width for the same profile area
(d) Improve flow of coolant around the fin
Answer: B
29. The critical radius of insulation of cylinder is given by
(a) k/h
(b) 2k/h
(c) k/2h
(d) k/4h
Answer: A
30. To reduce the heat loss with insulation in sphere the following condition should be satisfied
(a) r insulation thickness >> r critical
(b) r insulation thickness << rย critical
(c) r insulation thickness = F critical
(d) r insulation thickness = 0
Answer: A
31. The outer surface of a long cylinder is maintained at constant temperature . The cylinder does not have any heat source the temperature in the cylinder will
(a) Increase linearly with radius
(b) Decrease linearly with radius
(c) Be independent of radius
(d) Vary logarithmically with radius
Answer: D
32. On heat transfer surface , fins are provided
(a) To increase temperature gradient so as to enhance heat transfer
(b) To increase turbulence in flow for enhancing heat transfer
(c) To increase surface area to promote the rate of heat transfer
(d) To decrease the pressure drop of the fluid
Answer: C
33. Stefan Boltzmann Law is applicable for heat transfer by :
(a) Conduction
(b) Convection
(c) Radiation
(d) All of these
Answer: C
34. Steady State Heat Flow implies
(a) Negligible flow of heat
(b) No difference of temperature between the bodies
(c) Constant heat flow rate i.e, heat flow rate independent of time
(d) Uniform rate in temperature rise of a body
Answer: C
35. The ratio of thermal conductivity to electrical conductivity is equal to
(a) Prandtl number
(b) Schmidt number
(c) Lorentz number
(d) Lewis number
Answer: C
36. The unit of a following parameter is not mยฒ/s
(a) Thermal diffusivity
(b) Kinematic viscosity
(c) Mass diffusivity
(d) Dynamic viscosity
Answer: D
37. Which of the following fluid flow condition has high heat transfer coefficient?
(a) Free convection in air
(b) Forced convection in air
(c) Free convection in water
(d) Condensation of steam
Answer: D
38. The Prandtl number for liquid , which has velocity boundary layer much thicker than thermal boundary layer , is
(a) Pr >> 1
(b) Pr โ 1
(c) Pr << 1
(d) Pr = 0
Answer: A
39. The substance for which Prandtl number (Pr) << 1 is characterized by
(a) High rate of heat diffusion
(b) Low rate of heat diffusion
(c) High rate of mass diffusion
(d) Low rate of mass diffusion
Answer: A
40. For the fully developed laminar flow and heat transfer in a uniformly heated long circular tube , if the flow velocity is doubled and the tube diameter is halved , the heat transfer coefficient will be
(a) Double of the original value
(b) Half of the original value
(c) Same as before
(d) Four times of the original value
Answer: A
41. What is the ratio of thermal conductivity to electrical conductivity equal to?
(a) Prandtl number
(b) Schmidt number
(c) Lorenz number
(d) Lewis number
Answer: C
42. The predominant method of heat transfer that causes a pot of water to boil is:
(a) Conduction
(b) Radiation
(c) Convection
(d) Boiling
Answer: C
43. The fact that , in general , liquid and gases expand when heated gives rise to
(a) Convection currents in fluid due to changing masses
(b) Convection currents in fluids due to changing densities
(c) Heat transfer by conduction
(d) Convection currents in fluids due to constant temperatures
Answer: B
44. Stefen Boltzman law is applicable to
(a) Gray body
(b) White body
(c) Black body
(d) Blue body
Answer: C
45. All radiations in a black body are
(a) Reflected
(b) Refracted
(c) Transmitted
(d) Absorbed
Answer: D
46. Absorptivity of a body is equal to its emissivity
(a) For a polished body
(b) Under thermal equilibrium
(c) At one particular temperature
(d) At shorter wavelengths
Answer: B
47. A perfect black body is
(a) One which absorbs total radiant energy
(b) Black in colour
(c) One which does not reflect the radiant energy
(d) One which absorbs all radiant energy at all wavelengths
Answer: A
48. Which one of the following modes of heat transfer would take place predominantly from boiler furnace to water wall?
(a) Convection
(b) Conduction
(c) Radiation
(d) Conduction and Convection
Answer: C
49. Ice is very close to a
(a) Gray body
(b) Black body
(c) White body
(d) Specular body
Answer: B
50. A satellite in deep space with very high velocity . It will continuously lose heat by
(a) Convection
(b) Conduction and Convection
(c) Radiation
(d) Radiation and Convection
Answer: C
51. Intensity of radiation at a surface in perpendicular direction is equal to
(a) Product of emissivity of surface and 1/ฯ
(b) Product of emissivity of surface and ฯ
(c) Product of emissive power of surface and 1/ฯ
(d) Product of emissive power of surface and ฯ
Answer: C
52. If the temperature of a solid surface changes from 27ยฐC to 627ยฐC then its emissive power changes in which ratio?
(a) 6 : 1
(b) 9 : 1
(c) 27 : 1
(d) 81 : 1
Answer: D
53. The value of solar constant is.
(a) 1353 kW/mยฒ
(b) 1353 W/mยฒ
(c) 1353 J/mยฒ
(d) 135 kJ/mยฒ
Answer: B
54. “At thermal equilibrium , the ratio of the total emissive power to the total absorptivity is constant for all bodies” is known as
(a) Kirchhoff’s law
(b) Wien’s displacement law
(c) Maxwell’s theory
(d) Stefan Boltzmann law
Answer: A
55. Maximum spectral emissive power at temperature (T) is proportional to
(a) T^4
(b) T^5
(c) T^5/2
(d) T^3
Answer: B
56. The radiation energy emitted by the Sun between the wavelength of 0.4 ยตm to 0.76 ยตm is known as
(a) Ultraviolet radiation
(b) Infrared radiation
(c) Thermal radiation
(d) Visible radiation
Answer: D
57. The peak frequency at which energy is radiated from a blackbody radiator is dependent on
(a) Color
(b) Distance
(c) Intensity
(d) Temperature
Answer: D
58. Fraction of radiative energy leaving one surface that strikes the other surface is called
(a) Radiative flux
(b) Emissive power of the first surface
(c) View factor
(d) Re-radiation flux
Answer: C
59. Radiation of a black body , in terms of its temperature follows :
(a) Newton’s Law of cooling
(b) Plank’s Law
(c) Stefan’s law
(d) Einstein Bose equation
Answer: C
60. A static fluid can have
(a) Zero normal stress and non-zero shear stress
(b) Non-zero normal stress and non-zero shear stress
(c) Negative normal stress and zero shear stress
(d) Positive normal stress and non-zero shear stress
Answer: C
61. Mercury does not wet the glass . This is due to the property of the liquid known as –
(a) Cohesion
(b) Surface tension
(c) Adhesion
(d) Viscosity
Answer: A
62. One Poiseuille is equivalent to _____ poise .
(a) 1
(b) 100
(c) 1000
(d) 10
Answer: D
63. The ratio of dynamic viscosity to mass density is known as
(a) Kinematic viscosity
(b) Specific viscosity
(c) Coefficient of viscosity
(d) Viscosity index
Answer: A
64. What is the mass of a unit volume of substance called?
(a) Pressure
(b) Force
(c) Buoyancy
(d) Density
Answer: D
65. Fluid is a substance which offers no resistance of change of
(a) Volume
(b) Pressure
(c) Shape
(d) Flow
Answer: C
66. Pascal – second is the unit of
(a) Pressure
(b) Kinematic pressure
(c) Dynamic viscosity
(d) Surface tension
Answer: C
67. Poise can also be expressed as
(a) Dyne-cm/sยฒ
(b) Dyne-cm/s
(c) Dyne-s/cmยฒ
(d) Dyne-s/cmยณ
Answer: C
68. Spherical shape of droplets of mercury is due to
(a) high density
(b) High surface tension
(c) High adhesion
(d) Water
Answer: B
69. Milk mixes with water due to
(a) Very good cohesion
(b) Very good adhesion
(c) Very good surface tension
(d) Very good vapour surface
Answer: B
70. An ideal fluid
(a) Obey’s Newton’s law of viscosity
(b) Is both incompressible and non – viscous
(c) Is non viscous
(d) Frictionless and compressible
Answer: B
71. The dimensions of dynamic viscosity are
(a) ML-ยนT-ยฒ
(b) ML-ยนT-ยน
(c) MLT-ยฒ
(d) MยบLยบTยบ
Answer: C
72. The capillary depression in mercury is on account of
(a) Adhesion being larger than the viscosity
(b) Surface tension being larger than the viscosity
(c) Cohesion being greater than the adhesion
(d) Vapour pressure being small
Answer: C
73. The capillary rise at 20ยฐ in clean glass tube of 1mm diameter , containing water is
(a) 15 mm
(b) 50 mm
(c) 20 mm
(d) 30 mm
Answer: D
74. Newton’s law of viscosity depends upon the
(a) Stress and strain in the fluid
(b) Shear stress , pressure and velocity
(b) Shear stress and rate of strain
(d) Viscosity and shear stress
Answer: C
75. Which one of the following is defined as force per unit length
(a) Surface tension
(b) Compressibility
(c) Capillarity
(d) Viscosity
Answer: A
76. The specific gravity of water is taken as
(a) 0.001
(b) 0.01
(c) 0.1
(d) 1
Answer: D
77. Falling drops of water become spheres due to the property of
(a) Surface tension of water
(b) Compressibility of water
(c) Capillarity of water
(d) Viscosity of water
Answer: A
78. The liquid used in manometer should have
(a) Low density
(b) High density
(c) Low surface tension
(d) High surface tension
Answer: B
79. If the dynamic viscosity of a fluid is 0.5 poise and specific gravity is 0.7 , then kinematic viscosity of that fluid in stokes is
(a) 0.25
(b) 0.50
(c) 1.0
(d) 2.0
Answer: C
80. The variation in the volume of a liquid with the variation of pressure is called its
(a) Surface tension
(b) Compressibility
(c) Capillarity
(d) Viscosity
Answer: B
81. The intensity of pressure developed by surface tension of 0.075 N/m in a droplet of water of 0.075 mm diameter is
(a) 0.8 N/cmยฒ
(b) 0.6 N/cmยฒ
(c) 0.4 N/cmยฒ
(d) 400 N/cmยฒ
Answer: C
82. The point at which the resultant pressure on an immersed surface acts , is known as
(a) Centre of gravity
(b) Centre of depth
(c) Centre of pressure
(d) Centre of immersed surface
Answer: C
83. The property , which characterized the resistance which a fluid offers to applied shear force is called as
(a) Relative density
(b) Elasticity
(c) Fluidity
(d) Viscosity
Answer: D
84. Capillarity of liquid in small diameter tubes is due to molecular attraction . In case of Mercury , the following occurs in terms of capillarity
(a) Capillary rise
(b) Capillary depression
(c) Capillary flattening
(d) Compressibility
Answer: B
85. If a substance resists shear stress by elastic deformation , then the substance is
(a) Fluid
(b) Liquid
(c) Solid
(d) Gas
Answer: C
86. In general , surface tension
(a) Remains unaffected by temperature up to critical temperature
(b) Remains unaffected by temperature
(c) Increases with increase in temperature
(d) Decreases with increase of temperature
Answer: D
87. When a particle is suspended in water , two forces are acting on it , which are
(a) Gravity and drag force
(b) Gravity and buoyant force
(c) Buoyant and drag force
(d) Viscous and buoyant force
Answer: B
88. A fluid flow in which the density of the fluid changes significantly during flow is called as
(a) Incompressible
(b) Uniform
(c) Compressible
(d) Non – linear
Answer: C
89. What percent of the total volume of an iceberg floats above the water surface? Assume the density of ice to be 920 kg/m and the density of water to be 1000 kg/m .
(a) 20
(b) 92
(c) 6
(d) 8
Answer: D
90. Pascal’s law states that pressure at a point is equal in all directions in a/an
(a) Laminar flow
(b) Turbulent flow
(c) Inviscid flow
(d) Fluid at rest
Answer: D
91. What is the unit of pressure?
(a) Kelvin
(b) Newton
(c) Kg
(d) Pascal
Answer: D
92. Gauge pressure at a point is equal to ______ .
(a) Absolute pressure + atmospheric pressure
(b) Absolute pressure – atmospheric pressure
(c) Vacuum pressure + absolute pressure
(d) Vacuum pressure – atmospheric pressure
Answer: B
93. When a fluid is at rest , the shear stress is
(a) Undefined
(b) Zero
(c) Very large
(d) Finite
Answer: B
94. The liquid used in manometers should have
(a) Low density
(b) High density
(c) Low surface tension
(d) High surface tension
Answer: B
95. Absolute pressure in flow system
(a) Is always above local atmospheric pressure
(b) Is equal to a vacuum pressure
(c) May be above , below or equal to the local atmospheric pressure
(d) Is also called negative pressure
Answer: C
96. A barometer is used to measure
(a) Very low pressure
(b) Very High pressure
(c) Pressure difference between two points
(d) Atmospheric pressure
Answer: D
97. Which of the following is correct?
(a) Absolute pressure = gauge pressure + atmospheric pressure
(b) Gauge pressure = absolute pressure + atmospheric pressure
(c) Atmospheric pressure = absolute pressure + gauge pressure
(d) Absolute pressure = gauge pressure – atmospheric pressure
Answer: A
98. The piezometric head in a stationary and static liquid
(a) Remains constant only on the horizontal plane
(b) Increases non-linearly with depth below the surface
(c) Increases linearly with depth below the surface
(d) Remains constant at all the points in the fluid
Answer: A
99. Mercury is considered as superior barometric fluid chiefly due to its
(a) Negligible small vapour pressure
(b) High specific heat
(c) High specific gravity
(d) Convex meniscus
Answer: A
100. Bourdon gauge measures
(a) Absolute pressure
(b) Gauge pressure
(c) Local atmospheric
(d) Standard atmospheric pressure
Answer: B
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