mechanical engineering MCQs – Page 154

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

mechanical engineering Mcqs

1. compressors gas turbines and jet engines 2. theory of machines 3. nuclear power plants 4. engineering materials 5. strength of materials mechanical engineering 6. thermodynamics 7. heat transfer 8. i c engines 9. steam boilers engines nozzles and turbines 10. engineering mechanics 11. fluid mechanics mechanical engineering 12. production technology 13. machine design 14. hydraulic machines 15. workshop technology 16. refrigeration and air conditioning

3061. When heat is Transferred by molecular collision, it is referred to as heat transfer by __________________?
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A. convection and radiation

B. radiation

C. convection

D. scattering

E. conduction

3062. Heat transfer takes place as per ________________?
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A. first law of thermodynamic

B. zeroth law of thermodynamics

C. second law of the thermodynamics

D. Kirchoffs law E. Stefans law

3063. 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_________________?
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A. Krichoffs law

B. Black body law

C. Wien law

D. Stefans law

E. Plancks law

3064. In regenerator type heat exchanger, heat transfer takes place by___________________?
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A. a complete separation between hot and cold fluids

B. generation of heat again and again

C. direct mixing of hot and cold fluids

D. indirect transfer

E. flow of hot and cold fluids alternately over a surface

3065. The emissive power of a body depends upon its___________________?
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A. wave length

B. physical nature

C. all of the above

D. temperature

E. none of the above

3066. Total emissivity of polished silver compared to black body is___________________?
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A. more or less same

B. very much higher

C. higher

D. same

E. very much lower

3067. Which of the following property of air does not increase with rise in temperature ________________?
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A. thermal conductivity

B. density

C. thermal diffusivity

D. dynamic viscosity

E. kuiematic viscosity

3068. All radiations in a black body are___________________?
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A. reflected

B. transmitted

C. refracted

D. partly reflected and partly absorbed

E. absorbed

3069. The unit of overall coefficient of heat transfer is___________________?
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A. kacl/m hr C

B. kcal/hr C

C. kcal/m3 hr C

D. kcal/m2 hr C

E. kcal/m2

3070. The value of Prandtl number for air is about _______________________?
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A. 1.7

B. 10.5

C. 0.1

D. 0.7

E. 0.3

3071. Stefan Boltzmann law is applicable for heat transfer by __________________?
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A. conduction

B. convection

C. convection and radiation combined

D. radiation

E. conduction and radiation combined

3072. According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rate proportional to___________________?
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A. absolute temperature

B. fourth power of absolute temperature

C. cube of absolute temperature

D. square of temperature

E. fourth power of temperature

3073. According to Kirchoffs law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a _________________?
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A. grey body

B. brilliant white polished body

C. none of the above

D. black body

E. red hot body

3074. Depending on the radiating properties, a body will be opaque when _________________?
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A. p=l,x = 0anda = 0

B. x 0, a + p = 1

C. p = 0, x = 0 and a = 1

D. a=0,x + p= 1.

E. p = 0, x = 1 and a = 0

3075. If the temperature of a solid surface changes form 27C to 627C, then its emissive power changes in the ratio of___________________?
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A. 3

B. 6

C. 9

D. 27

E. 81

3076. The value of the wavelength for maximum emissive power is given by ___________________?
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A. Plancks law

B. Stefans law

C. Kirchhoffs law

D. Wiens law

E. Fouriers law

3077. According to Wiens law, the wavelength corresponding to maximum energy is proportion to ________________?
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A. absolute temperature (T)

B. I2

C. t

D. f

E. 1/r

3078. Two plates spaced 150 mm apart are maintained at 1000C and 70C. The heat transfer will take place mainly by ___________________?
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A. free convection

B. radiation and convection

C. convection

D. radiation

E. forced convection

3079. The ratio of the energy absorbed by the body to total energy falling on it is called_________________?
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A. absorptive power

B. absorptivity

C. none of the above

D. emissive power

E. emissivity

3080. Depending on the radiating properties, a body will be white when_________________?
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A. p=l,T = 0anda = 0

B. a = 0, x + p = 1.

C. p = 0, x = 1 and a = 0

D. p = 0, x = 0 and a = 1

E. x = 0, a + p = 1

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