Explore topic-wise MCQs in Mechanical Engineering.

This section includes 362 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.

301.

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
Answer» B. Lower
Discussion
302.

The thermal diffusivities for solids are generally$?

A. Less than those for gases
B. Less than those for liquids
C. More than those for liquids and gases
D. More or less same as for liquids and gases
Answer» D. More or less same as for liquids and gases
Discussion
303.

The heat transfer takes place according to$?

A. Zeroth law of thermodynamics
B. First law of thermodynamics
C. Second law of thermodynamics
D. Kirchhoff's law
Answer» D. Kirchhoff's law
Discussion
304.

According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the$?

A. Absolute temperature
B. Square of the absolute temperature
C. Cube of the absolute temperature
D. Fourth power of the absolute temperature
Answer» E.
Discussion
305.

Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature.$?

A. Minimum energy
B. Maximum energy
C. Both (A) and (B)
D. None of these
Answer» C. Both (A) and (B)
Discussion
306.

Which of the following has maximum value of thermal conductivity?$?

A. Aluminium
B. Steel
C. Brass
D. Copper
Answer» B. Steel
Discussion
307.

Fouling factor is used$?

A. In heat exchanger design as a safety factor
B. In case of Newtonian fluids
C. When a liquid exchanges heat with a gas
D. None of the above
Answer» B. In case of Newtonian fluids
Discussion
308.

Emissivity of a white polished body in comparison to a black body is$?

A. Higher
B. Lower
C. Same
D. Depends upon the shape of body
Answer» C. Same
Discussion
309.

The thermal diffusivities for solids are generally?

A. Less than those for gases
B. Less than those for liquids
C. More than those for liquids and gases
D. More or less same as for liquids and gases
Answer» D. More or less same as for liquids and gases
Discussion
310.

The heat transfer takes place according to?

A. Zeroth law of thermodynamics
B. First law of thermodynamics
C. Second law of thermodynamics
D. Kirchhoff's law
Answer» D. Kirchhoff's law
Discussion
311.

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
Answer» B. Lower
Discussion
312.

An ordinary passenger aircraft requires a cooling system of capacity.?

A. 2 TR
B. 4 TR
C. 8 TR
D. 10 TR
Answer» D. 10 TR
Discussion
313.

Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of?

A. 0.002
B. 0.02
C. 0.01
D. 0.1
Answer» C. 0.01
Discussion
314.

Thermal conductivity of water in general with rise in temperature?

A. Increases
B. Decreases
C. Remain constant
D. May increase or decrease depending on temperature
Answer» E.
Discussion
315.

The value of the wave length for maximum emissive power is given by?

A. Kirchhoff’s law
B. Stefan’s law
C. Wine’s law
D. Planck’s law
Answer» D. Planck‚Äö√Ñ√¥s law
Discussion
316.

Reynolds number is the ratio of?

A. Energy transferred by convection to that by conduction
B. Kinematic viscosity to thermal diffusivity
C. Inertia force to viscous force
D. None of the above
Answer» D. None of the above
Discussion
317.

Fouling factor is used?

A. In heat exchanger design as a safety factor
B. In case of Newtonian fluids
C. When a liquid exchanges heat with a gas
D. None of the above
Answer» B. In case of Newtonian fluids
Discussion
318.

Emissivity of a white polished body in comparison to a black body is?

A. Higher
B. Lower
C. Same
D. Depends upon the shape of body
Answer» C. Same
Discussion
319.

Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature.?

A. Minimum energy
B. Maximum energy
C. Both (A) and (B)
D. None of these
Answer» C. Both (A) and (B)
Discussion
320.

Which of the following has maximum value of thermal conductivity??

A. Aluminium
B. Steel
C. Brass
D. Copper
Answer» B. Steel
Discussion
321.

According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the?

A. Absolute temperature
B. Square of the absolute temperature
C. Cube of the absolute temperature
D. Fourth power of the absolute temperature
Answer» E.
Discussion
322.

Thermal conductivity of glass wool varies from sample to sample because of variation in

A. Composition
B. Density
C. Porosity
D. All of the above
Answer» E.
Discussion
323.

The highest thermal diffusivity is of

A. Iron
B. Lead
C. Concrete
D. Wood
Answer» C. Concrete
Discussion
324.

When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,$

A. α = 1, ρ = 0 and τ = 0
B. α = 0, ρ = 1 and τ = 0
C. α = 0, ρ = 0 and τ = 1
D. α + ρ = 1 and τ = 0
Answer» E.
Discussion
325.

Temperature of steam at around 540°C can be measured by$

A. Thermometer
B. Thermistor
C. Thermocouple
D. None of these
Answer» D. None of these
Discussion
326.

The rate of heat flow through a body is Q = [kA (T‚ÇÅ - T‚ÇÇ)]/x. The term x/kA is known as$

A. Thermal coefficient
B. Thermal resistance
C. Thermal conductivity
D. None of these
Answer» C. Thermal conductivity
Discussion
327.

According to Dalton's law of partial pressures, (where pb = Barometric pressure, pa = Partial pressure of dry air, and pv = Partial pressure of water vapour)

A. Pb = pa - pv
B. Pb = pa + pv
C. Pb = pa √ó pv
D. Pb = pa/pv
Answer» C. Pb = pa ‚àö√≥ pv
Discussion
328.

Unit of thermal conductivity in S.I. units is

A. J/m² sec
B. J/m °K sec
C. W/m °K
D. Option (B) and (C) above
Answer» E.
Discussion
329.

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
Answer» E.
Discussion
330.

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
Answer» B. Inferior insulation should be put over pipe and better one over it
Discussion
331.

The amount of radiation mainly depends upon the

A. Nature of the body
B. Temperature of the body
C. Type of surface of the body
D. All of these
Answer» E.
Discussion
332.

In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in

A. Parallel flow
B. Counter flow
C. Cross flow
D. All of these
Answer» E.
Discussion
333.

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles due to difference of density caused by temperature of the particle is known as

A. Conduction
B. Free convection
C. Forced convection
D. Radiation
Answer» C. Forced convection
Discussion
334.

Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

A. k. A. (dT/dx)
B. k. A. (dx/dT)
C. k. (dT/dx)
D. k. (dx/dT)
Answer» B. k. A. (dx/dT)
Discussion
335.

Radiation is the process of heat transfer in which heat flows from a ________, in a straight line, without affecting the intervening medium.

A. Cold body to hot body
B. Hot body to cold body
C. Smaller body to larger body
D. Larger body to smaller body
Answer» C. Smaller body to larger body
Discussion
336.

The heat is transferred by conduction, convection and radiation in

A. Melting of ice
B. Boiler furnaces
C. Condensation of steam in condenser
D. None of these
Answer» C. Condensation of steam in condenser
Discussion
337.

The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

A. Move actually
B. Do not move actually
C. Affect the intervening medium
D. Does not affect the intervening medium
Answer» C. Affect the intervening medium
Discussion
338.

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
Answer» B. 0.55
Discussion
339.

Sensible heat factor is given by (where S.H. = Sensible heat, and L.H. = Latent heat)

A. S.H/(S.H + L.H)
B. (S.H + L.H) /S.H
C. (L.H - S.H)/S.H
D. S.H/(L.H - S.H)
Answer» B. (S.H + L.H) /S.H
Discussion
340.

Reynolds number (RN) is given by (where h = Film coefficient, l = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, ρ = Density of fluid, cp = Specific heat at constant pressure, and μ = Coefficient of absolute viscosity)$

A. RN = hl/k
B. RN = μ cp/k
C. RN = ρ V l /μ
D. RN = V²/t.cp
Answer» D. RN = V¬¨‚â§/t.cp
Discussion
341.

Thermal conductivity of water at 20°C is of the order of$

A. 0.1
B. 0.23
C. 0.42
D. 0.51
Answer» E.
Discussion
342.

The heat transfer by conduction through a thick sphere is given by

A. Q = 2πkr1 r2 (T1 - T2)/ (r2 - r1)
B. Q = 4πkr1 r2 (T1 - T2)/ (r2 - r1)
C. Q = 6πkr1 r2 (T1 - T2)/ (r2 - r1)
D. Q = 8πkr1 r2 (T1 - T2)/ (r2 - r1)
Answer» C. Q = 6≈ì√Ñkr1 r2 (T1 - T2)/ (r2 - r1)
Discussion
343.

A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

A. A.Cmin/U
B. U/A.Cmin
C. A.U.Cmin
D. A.U/Cmin
Answer» E.
Discussion
344.

The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit)$

A. tm = (Δt1 - Δt2)/ loge (Δt1/Δt2)
B. tm = loge (Δt1/Δt2)/ (Δt1 - Δt2)
C. tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2)
D. tm = loge (Δt1 - Δt2)/ Δt1/Δt2
Answer» B. tm = loge (≈í√Æt1/≈í√Æt2)/ (≈í√Æt1 - ≈í√Æt2)
Discussion
345.

In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

A. Convection
B. Radiation
C. Conduction
D. Both convection and conduction
Answer» D. Both convection and conduction
Discussion
346.

Which of the following is expected to have highest thermal conductivity?

A. Steam
B. Solid ice
C. Melting ice
D. Water
Answer» C. Melting ice
Discussion
347.

The transfer of heat by molecular collision is smallest in

A. Solids
B. Liquids
C. Gases
D. None of these
Answer» D. None of these
Discussion
348.

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
Answer» D. Generation of heat again and again
Discussion
349.

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

A. Conduction
B. Free convection
C. Forced convection
D. Radiation
Answer» D. Radiation
Discussion
350.

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
Answer» D. 4: 1
Discussion