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.

101.

Joule sec is the unit of_________________?
A. universal gas constant
B. kinematic viscosity
C. thermal conductivity
D. Planck’s constant
E. none of the above
Answer» E. none of the above
Discussion
102.

According to Kirchoff’s law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a _________________?
A. grey body
B. brilliant white polished body
C. red hot body
D. black body
E. none of the above
Answer» E. none of the above
Discussion
103.

Generally, thermal conductivity of liquids is
A. very high
B. very small
C. varies from very small to very high
D. unpredictable
Answer» C. varies from very small to very high
Discussion
104.

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
E. none of the above
Answer» D. both convection and conduction
Discussion
105.

In heat exchangers, degree of approach is defined as the difference between temperatures of________________?
A. cold water inlet and outlet
B. hot medium inlet and outlet
C. hot medium outlet and cold water inlet
D. hot medium outlet and cold water outlet
E. none of the above
Answer» E. none of the above
Discussion
106.

A grey body is one whose absorptivity_________________?
A. varies with temperature
B. varies with wavelength of the incident ray
C. is equal to its emissivity
D. does not vary with temperature and. wavelength of the incident ray
E. none of the above
Answer» D. does not vary with temperature and. wavelength of the incident ray
Discussion
107.

Film coefficient is defined as Inside diameter of tube________________?
A. Equivalent thickness of film
B. Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
C. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
D. Film coefficient x Inside diameter Thermalconductivity
E. none of the above
Answer» C. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
Discussion
108.

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
E. none of the above
Answer» C. same
Discussion
109.

Unit of thermal diffusivity is_________________?
A. m2/hr
B. m2/hr°C
C. kcal/m2 hr
D. kcal/m.hr°C
E. kcal/m2 hr°C
Answer» B. m2/hr°C
Discussion
110.

Heat conducted througfi unit area and unit thick face per unit time when temperature difference between opposite faces is unity,is called__________________?
A. thermal resistance
B. thermal coefficient
C. temperature gradient
D. thermal conductivity
E. heat-transfer
Answer» E. heat-transfer
Discussion
111.

Depending on the radiating properties, a body will be white 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 = 1
E. a = 0, x + p = 1.
Answer» C. p = 0, x = 1 and a = 0
Discussion
112.

Depending on the radiating properties, a body will be opaque when _________________?
A. p = 0, x = 0 and a = 1
B. p=l,x = 0anda = 0
C. p = 0, x = 1 and a = 0
D. x – 0, a + p = 1
E. a=0,x + p= 1.
Answer» E. a=0,x + p= 1.
Discussion
113.

The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as_________________?
A. Krichoff’s law
B. Stefan’s law
C. Wien’ law
D. Planck’s law
E. Black body law
Answer» B. Stefan’s law
Discussion
114.

Which of the following has least value of conductivity_________________?
A. glass
B. water
C. plastic
D. rubber
E. air
Answer» F.
Discussion
115.

According to Prevost theory of heat exchange ___________________?
A. it is impossible to transfer heat from low temperature source to t high temperature source
B. heat transfer by radiation requires no medium
C. all bodies above absolute zero emit radiation
D. heat transfer in most of the cases takes place by combination of conduction, convection and radiation
E. rate of heat transfer depends on thermal conductivity and temperature difference
Answer» D. heat transfer in most of the cases takes place by combination of conduction, convection and radiation
Discussion
116.

Thermal conductivity of air with rise in temperature__________________?
A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. none of the above
Answer» B. decreases
Discussion
117.

Thermal conductivity of glass-wool varies from sample to sample because of variation in ________________ ?
A. composition
B. density
C. porosity
D. structure
E. all of the above
Answer» F.
Discussion
118.

Heat flows from one body to other when they have_________________?
A. different heat contents
B. different specific heat
C. different atomic structure
D. different temperatures
E. none of the above
Answer» E. none of the above
Discussion
119.

The time constant of a thermocouple is_______________?
A. the time taken to attain the final temperature to be measured
B. the time taken to attain 50% of the value of initial temperature difference
C. the time taken to attain 63.2% of the value of initial temperature difference
D. determined by the time taken to reach 100°C from 0°C
E. none of the above
Answer» D. determined by the time taken to reach 100°C from 0°C
Discussion
120.

Thermal conductivity of water at 20°C is of the order of_____________________?
A. 0.1
B. 0.23
C. 0.42
D. 0.51
E. 0.64
Answer» E. 0.64
Discussion
121.

Thermal conductivity of a material may be defined as the________________?
A. quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
B. quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1�
C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D. all of the above
E. none of the above
Answer» E. none of the above
Discussion
122.

In heat transfer, conductance equals conductivity (kcal/hr/sqm/°C/cm) divided by ________________?
A. hr (time)
B. sqm (area)
C. °C (temperature)
D. cm (thickness)
E. kcal (heat).
Answer» E. kcal (heat).
Discussion
123.

Which of the following is expected to have highest thermal conductivity_______________?
A. steam
B. solid ice
C. melting ice
D. water
E. boiling water
Answer» C. melting ice
Discussion
124.

Total heat is the heat required to__________________?
A. change vapour into liquid
B. change liquid into vapour
C. increase the temperature of a liquid or vapour
D. convert water into steam and superheat it
E. convert saturated steam into dry steam
Answer» E. convert saturated steam into dry steam
Discussion
125.

When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by ___________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation
Answer» B. convection
Discussion
126.

Heat is closely related with___________________?
A. liquids
B. energy
C. temperature
D. entropy
E. enthalpy
Answer» D. entropy
Discussion
127.

Heat is transferred by all three modes of transfer, viz, conduction, convection and radiation in _________________?
A. electric heater
B. steam condenser
C. melting of ice
D. refrigerator condenser coils
E. boiler
Answer» F.
Discussion
128.

Unit of thermal conductivity in S.I. units is__________________?
A. J/m2 sec
B. J/m °K sec
C. W/m °K
D. A. and C. above
E. B. and C. above
Answer» F.
Discussion
129.

When heat is transferred form hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by __________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation
Answer» D. conduction and convection
Discussion
130.

Heat transfer takes place as per ________________?
A. zeroth law of thermodynamics
B. first law of thermodynamic
C. second law of the thermodynamics
D. Kirchoff’s law E. Stefan’s law
Answer» D. Kirchoff’s law E. Stefan’s law
Discussion
131.

The insulation ability of an insulator with the presence of moisture would_________________?
A. increase
B. decrease
C. remain unaffected
D. may increase/decrease depending on temperature and thickness of insulation
E. none of the above
Answer» C. remain unaffected
Discussion
132.

In desert areas, there is large difference between day and night temperatures mainly because of
A. presence of carbon dioxide in air as it acts as barrier for emanating infrared radiation from the earth surface
B. presence of water vapour in air as it acts as barrier for emanating infrared radiation from the earth surface
C. absence of carbon dioxide in air as it acts as barrier for emanating infrared radiation from the earth surface
D. absence of water vapour in air as it acts as barrier for emanating infrared radiation from the earth surface
Answer» E.
Discussion
133.

How is the cooling at night in coastal areas?
A. the day temperature reduces rapidly at night in coastal areas
B. the day temperature reduces slowly at night in coastal areas
C. the day temperature and a night temperature in coastal areas are similar
D. unpredictable
Answer» C. the day temperature and a night temperature in coastal areas are similar
Discussion
134.

In parallel flow heat exchangers,
A. the exit temperature of hot fluid is always equal to the exit temperature of cold fluid
B. the exit temperature of hot fluid is always less than the exit temperature of cold fluid
C. the exit temperature of hot fluid is always more than the exit temperature of cold fluid
D. we cannot predict comparison between exit temperatures of hot fluid and cold fluid
Answer» D. we cannot predict comparison between exit temperatures of hot fluid and cold fluid
Discussion
135.

Thermal conductivity of non-metallic amorphous solids with decrease in temperature __________________?
A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. unpredictable
Answer» C. remains constant
Discussion
136.

For the same inlet and exit temperatures of two fluids, the LMTD for counterflow is always
A. smaller than LMTD for parallel flow
B. greater than LMTD for parallel flow
C. same as LMTD for parallel flow
D. unpredictable
Answer» C. same as LMTD for parallel flow
Discussion
137.

The radiation from fusion of hydrogen
A. can be achieved on earth's surface
B. cannot be achieved on earth's surface
C. can be achieved on earth's surface at high maintained temperature
D. unpredictable
Answer» C. can be achieved on earth's surface at high maintained temperature
Discussion
138.

The rate at which the solar energy reaching the earth's atmosphere is called as
A. solar constant
B. radiation constant
C. electromagnetic constant
D. atmospheric constant
Answer» B. radiation constant
Discussion
139.

The radiation energy from the sun is produced by
A. fission reaction
B. fusion reaction
C. both a. and b.
D. none of the above
Answer» C. both a. and b.
Discussion
140.

Gases absorb and emit radiant energy
A. in all wavelengths over the entire spectrum (λ = 0 to ∞)
B. only between narrow ranges of wavelengths
C. only at single constant wavelength
D. unpredictable
Answer» C. only at single constant wavelength
Discussion
141.

Which surface can be best described as a radiation shield?
A. the surface which has very high absorptivity
B. the surface which has very high transmissivity
C. the surface which has very high reflectivity
D. none of the above
Answer» D. none of the above
Discussion
142.

Thermal conductivity of water in general with rise in temperature ____________________?
A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. none of the above
Answer» E. none of the above
Discussion
143.

What is the purpose of using fins in a particular heat transfer system?
A. to decrease rate of heat transfer
B. to increase rate of heat transfer
C. to maintain rate of heat transfer at a constant rate
D. cannot say
Answer» C. to maintain rate of heat transfer at a constant rate
Discussion
144.

What is lumped heat capacity analysis?
A. the analysis of a system in which it is assumed to be at no uniform temperature
B. the analysis of a system in which it is assumed to be at uniform temperature
C. the analysis of a system in which it is assumed to be at either uniform or no uniform temperature
D. none of the above
Answer» C. the analysis of a system in which it is assumed to be at either uniform or no uniform temperature
Discussion
145.

What is the correct formula for The Biot number?
A. hl/k
B. k/hl
C. l/hk
D. hk/l
Answer» B. k/hl
Discussion
146.

Suppose that a hot metal ball is suddenly immersed in cold water. What is the condition for the ball to maintain it at a uniform temperature?
A. the conduction resistance in a ball should be very large compared to the convection resistance for heat transfer from surface of ball to water
B. the conduction resistance in a ball should be very small compared to the convection resistance for heat transfer from surface of ball to water
C. the conduction resistance in a ball should be equal to the convection resistance for heat transfer from surface of ball to water
D. cannot say
Answer» C. the conduction resistance in a ball should be equal to the convection resistance for heat transfer from surface of ball to water
Discussion
147.

The Biot number or Biot modulus is given by
A. the ratio of external convection resistance to the internal conduction resistance
B. the ratio of internal conduction resistance to the external convection resistance
C. multiplying internal conduction resistance and external convection resistance
D. none of the above
Answer» C. multiplying internal conduction resistance and external convection resistance
Discussion
148.

Which medium of surrounding is better for fin effectiveness?
A. gas medium
B. liquid medium
C. fins have same effectiveness in both the gas and liquid mediums
D. none of the above
Answer» B. liquid medium
Discussion
149.

What is the effect of convective heat transfer coefficient h on fin effectiveness?
A. fin is effective if the value of convective heat transfer coefficient h is small
B. fin is effective if the value of convective heat transfer coefficient h is large
C. fin effectiveness does not affected by the value of convective heat transfer coefficient h
D. none of the above
Answer» B. fin is effective if the value of convective heat transfer coefficient h is large
Discussion
150.

What is the effect of thermal conductivity k on fin effectiveness?
A. fin is effective for smaller value of thermal conductivity k
B. fin is effective for larger value of thermal conductivity k
C. thermal conductivity k does not affect the fin effectiveness
D. cannot say
Answer» C. thermal conductivity k does not affect the fin effectiveness
Discussion