Explore topic-wise MCQs in Mechanical Engineering Questions.

This section includes 585 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.

51.

The amount of radiation mainly depends on___________________?
A. nature of body
B. temperature of body
C. type of surface of body
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
52.

The ratio of the energy absorbed by the body to total energy falling on it is called_________________?
A. absorptive power
B. emissive power
C. absorptivity
D. emissivity
E. none of the above
Answer» B. emissive power
Discussion
53.

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is____________________?
A. 0.45
B. 0.55
C. 0.40
D. 0.75
E. 0.60
Answer» B. 0.55
Discussion
54.

What is kinematics viscosity of a fluid?
A. dynamic viscosity per unit volume of the fluid
B. dynamic viscosity per unit weight of the fluid
C. dynamic viscosity per unit density of the fluid
D. none of the above
Answer» D. none of the above
Discussion
55.

Depending on the radiating properties, a body will be black when_________________?
A. p = 0, x = 0 and a = 1
B. p= l,T = 0anda = 0
C. p = 0, x = 1 and a = 0
D. x = 0, a + p = 0
E. a = 0,x + p= 1.
Answer» B. p= l,T = 0anda = 0
Discussion
56.

The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?
A. temperature
B. thickness
C. area
D. time
E. area and time
Answer» E. area and time
Discussion
57.

The emissive power of a body depends upon its___________________?
A. temperature
B. wave length
C. physical nature
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
58.

How does the radiation heat transfer occur through perfect vacuum?
A. by light waves
B. by electromagnetic waves
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
59.

Which of the following fluid can be considered as an ideal fluid?
A. viscous fluid
B. non-viscous fluid
C. compressible fluid
D. all of the above
Answer» C. compressible fluid
Discussion
60.

The viscosity of a liquid
A. increases with increase in liquid temperature
B. decreases with increase in liquid temperature
C. is not affected by the change in liquid temperature
D. is unpredictable
Answer» C. is not affected by the change in liquid temperature
Discussion
61.

How is the viscosity of gas affected by change in its temperature?
A. viscosity of a gas decreases with increase in temperature of gas
B. viscosity of a gas increases with increase in temperature of gas
C. viscosity of a gas is not affected by change in temperature of gas
D. viscosity of a gas is unpredictable
Answer» C. viscosity of a gas is not affected by change in temperature of gas
Discussion
62.

The heat transfer is largely governed by conduction from the surface of the fluid, when
A. the velocity of the fluid is high
B. the velocity of the fluid is small
C. the velocity of the fluid is small as well as high
D. none of the above
Answer» C. the velocity of the fluid is small as well as high
Discussion
63.

Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of____________________?
A. 1 :1
B. 2: 1
C. 1 : 2
D. 4 : 1
E. 1 : 4
Answer» D. 4 : 1
Discussion
64.

The rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as ________________?
A. emissivity
B. transmissivity
C. reflectivity
D. intensity of radiation
E. absorptivity
Answer» E. absorptivity
Discussion
65.

According to Wien’s law, the wavelength corresponding to maximum energy is proportion to ________________?
A. absolute temperature (T)
B. I2
C. f
D. t
E. 1/r
Answer» B. I2
Discussion
66.

A non-dimensional number generally associated with natural convection heat transfer is________________?
A. Grashoff number
B. Nusselt number
C. Weber number
D. Prandtl number
E. Reynold number
Answer» B. Nusselt number
Discussion
67.

The amount of heat flow through a body by conduction is_______________?
A. directly proportional to the surface area of the body
B. directly proportional to the temperature difference on the two faces of the body
C. dependent upon the material of the body
D. inversely proportional to the thickness of the body
E. all of the above
Answer» F.
Discussion
68.

Which theory is widely used to determine the heat transfer coefficient for film condensation on surfaces?
A. Reynold's theory
B. Grashof's theory
C. Nusselt's theory
D. Prandtl's theory
Answer» D. Prandtl's theory
Discussion
69.

What is the relation between temperature of a body and the wavelength of its emitted radiation at its maximum emissive power?
A. as temperature of a body increases the wavelength of its emitted radiation also increases at its maximum emissive power
B. as temperature of a body increases the wavelength of its emitted radiation decreases at its maximum emissive power
C. as temperature of a body increases the wavelength of its emitted radiation does not change only at its maximum emissive power
D. none of the above
Answer» C. as temperature of a body increases the wavelength of its emitted radiation does not change only at its maximum emissive power
Discussion
70.

The values of reflectivity (ρ), absorptivity (α) and transmissivity (τ) of a body are depend upon
A. material of the body
B. surface condition of the body
C. wavelength of radiation
D. all of the above
Answer» E.
Discussion
71.

Gray body can emits radiation
A. at higher rate than the black body
B. at lower rate than the black body
C. at equal rate than the black body
D. cannot predict
Answer» C. at equal rate than the black body
Discussion
72.

At a given temperature if wavelengths are changed, the quality of radiation per unit wavelength
A. will always be constant
B. will also be changed
C. will be changed sometimes but sometimes be constant
D. unpredictable
Answer» C. will be changed sometimes but sometimes be constant
Discussion
73.

Which of the following relation is correct for the radiation?
A. [Incident Radiation] + [Absorbed Radiation] = [Reflected Radiation] + [Transmitted Radiation]
B. [Incident Radiation] + [Transmitted Radiation] = [Reflected Radiation] + [Absorbed Radiation]
C. [Incident Radiation] = [Reflected Radiation] + [Absorbed Radiation] + [Transmitted Radiation]
D. [Absorbed Radiation] = [Reflected Radiation] + [Transmitted Radiation] + [Incident Radiation]
Answer» D. [Absorbed Radiation] = [Reflected Radiation] + [Transmitted Radiation] + [Incident Radiation]
Discussion
74.

Suppose a hot water is placed inside a closed metal vessel of thickness 5 mm. There is atmospheric air outside the vessel at temperature lower than the temperature of hot water. The heat is transferred from the hot water to atmospheric air. What is the mode of heat transfer in this condition?
A. conduction then convection
B. convection then conduction
C. convection then conduction then convection
D. conduction then convection then conduction
Answer» D. conduction then convection then conduction
Discussion
75.

According to the Nusselt's theory, to determine the heat transfer coefficient for film condensation on surfaces,
A. the vapour should be pure, dry and saturated
B. the condensate flow should be laminar
C. heat transfer should be at steady state
D. all of the above
Answer» E.
Discussion
76.

The eddy properties are used in turbulent boundary layer condition because
A. the eddy properties may be small compared to molecular properties
B. the eddy properties may be large compared to molecular properties
C. the eddy properties may be small or may be large compared to molecular properties, but never equals to molecular properties
D. none of the above
Answer» C. the eddy properties may be small or may be large compared to molecular properties, but never equals to molecular properties
Discussion
77.

Convective heat transfer coefficient is also known as
A. film convection factor
B. film coefficient
C. film conductance
D. none of the above
Answer» D. none of the above
Discussion
78.

What should be the temperature of black body to emit radiant energy which is independent of the conditions in the surroundings?
A. temperature of black body should be less than zero
B. temperature of black body should be more than zero
C. temperature of black body should be equal to zero
D. all of the above
Answer» C. temperature of black body should be equal to zero
Discussion
79.

What is the mode of heat transfer from the hot surface to the adjacent layer of fluid which surrounds the surface?
A. conduction mode of heat transfer
B. radiation mode of heat transfer
C. convection mode of heat transfer
D. none of the above
Answer» B. radiation mode of heat transfer
Discussion
80.

The current in the electrical system is analogous to
A. the temperature in the heat transfer system
B. the heat flow in the heat transfer system
C. the thermal conductance in the heat transfer system
D. the thermal resistance in the heat transfer system
Answer» C. the thermal conductance in the heat transfer system
Discussion
81.

What is the relation between reflectivity (ρ), absorptivity (α) and transmissivity (τ)?
A. ρ – α + τ = 1
B. ρ + α – τ = 1
C. ρ + α + τ = 1
D. ρ – α – τ = 1
Answer» D. ρ – α – τ = 1
Discussion
82.

In turbulent flow of the fluid,
A. conduction becomes more important
B. conduction becomes less important
C. doesn't matter
D. none of the above
Answer» C. doesn't matter
Discussion
83.

What is diffuse reflection of radiation?
A. the reflection of radiation on a rough surface which occurs in all directions
B. the reflection of radiation on a rough surface which occurs in a single direction
C. the reflection of radiation on a smooth surface
D. none of the above
Answer» B. the reflection of radiation on a rough surface which occurs in a single direction
Discussion
84.

What is the opaque body?
A. the body which does not reflect radiation
B. the body which does not absorb radiation
C. the body which does not transmit radiation
D. all of the above
Answer» D. all of the above
Discussion
85.

The thermal diffusivities for gases are generally_____________________?
A. more than those for liquids
B. less than those for liquids
C. more than those for solids
D. dependent on the viscosity
E. same as for the liquids
Answer» B. less than those for liquids
Discussion
86.

The reflection in which the angle of incident is equal to the angle of reflection is called as
A. regular reflection
B. specular reflection
C. both a. and b.
D. none of the above
Answer» D. none of the above
Discussion
87.

Generally, the convection heat transfer coefficient in drop-wise condensation is
A. lower than the convection heat transfer coefficient in film condensation
B. higher than the convection heat transfer coefficient in film condensation
C. equal to the convection heat transfer coefficient in film condensation
D. unpredictable
Answer» C. equal to the convection heat transfer coefficient in film condensation
Discussion
88.

Thermal diffusivity of a substance is __________________?
A. directly proportional to thermal con¬ductivity
B. inversely proportional to density of substance
C. inversely proportional to specific heat
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
89.

Surface coating is suitable to maintain
A. drop-wise condensation
B. film condensation
C. both drop-wise and film condensation
D. none of the above
Answer» B. film condensation
Discussion
90.

Planck’s law holds good for________________?
A. black bodies
B. polished bodies
C. all coloured bodies
D. all of the above
E. none of the above
Answer» B. polished bodies
Discussion
91.

A grey body is one whose absorptivity _________________?
A. varies with temperature
B. varies with the wave length of incident ray
C. varies with both
D. does not vary with temperature and wave length of the incident ray
E. there is no such criterion
Answer» E. there is no such criterion
Discussion
92.

If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of___________________?
A. 3
B. 6
C. 9
D. 27
E. 81
Answer» F.
Discussion
93.

Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by ___________________?
A. convection
B. free convection
C. forced convection
D. radiation
E. radiation and convection
Answer» E. radiation and convection
Discussion
94.

Fourier’s law of heat conduction is valid for_________________?
A. one dimensional cases only
B. two dimensional cases only
C. three dimensional cases only
D. regular surfaces having non-uniform temperature gradients
E. irregular surfaces
Answer» B. two dimensional cases only
Discussion
95.

In regenerator type heat exchanger, heat transfer takes place by___________________?
A. direct mixing of hot and cold fluids
B. a complete separation between hot and cold fluids
C. flow of hot and cold fluids alternately over a surface
D. generation of heat again and again
E. indirect transfer
Answer» D. generation of heat again and again
Discussion
96.

In counter flow heat exchangers_________________?
A. both the fluids at inlet (of heat ex¬changer where hot fluid enters) are in their coldest state
B. both the fluids at inlet are in their hot¬test state
C. both the fluids .at exit are in their hottest state
D. one fluid is in hottest state and other in coldest state at inlet
E. any combination is possible depending on design of heat exchanger
Answer» C. both the fluids .at exit are in their hottest state
Discussion
97.

The concept of overall coefficient of heat transfer is used in case of heat transfer by________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation
Answer» E. convection and radiation
Discussion
98.

A steam pipe is to be insulated by two insulating materials put over each other . For best results__________________?
A. better insulation should be put over pipe and better one over it
B. inferior insulation should be put over pipe and better one over it
C. both may be put in any order
D. whether to put inferior OIL over pipe or the better one would depend on steam temperature
E. unpredictable
Answer» B. inferior insulation should be put over pipe and better one over it
Discussion
99.

LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is _________________?
A. higher
B. lower
C. same
D. depends on the area of heat exchanger
E. depends on temperature conditions
Answer» B. lower
Discussion
100.

According of Kirchhoff’s law______________________?
A. radiant heat is proportional to fourth power of absolute temperature
B. emissive power depends on temperature
C. emissive power and absorptivity are constant for all bodies
D. ratio of emissive power to absorptive power is maximum for perfectly black body
E. ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body
Answer» F.
Discussion