## HEAT AND MASS TRANSFER MCQ

**SECTION-3**

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**Q61. ‘The total emissive power for any body at a given temperature is equal to its absorptivity multiplied by the total emissive power of a perfect black body at the same temperature’— this statement is known as**

(a) Wien’s law

(b) Planck’s law

(c) Kirchhoff’s law

(d) Stefan Boltzman law.

**Q62. The ratio of total emissive power of a body to the total emissive power of a black body is called**

(a) absorptivity

(b) reflectivity

(c) transmissivity

(d) emissivity.

**Q63. If the ratio of emission of a body to that of a black body at a given temperature is constant for all wavelengths, the body is called**

(a) black body

(b) grey body

(c) white body

(d) opaque body.

**Q64. The heat transfer, from one particle of a fluid to another by the actual motion (which is caused by the difference in density due to temperature) of the particle known as**

(a) forced convection

(b) free convection

(c) artificial convection

(d) none of the above.

**Q65.The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be, the interface temperature at the end of the 2nd layer would be**

(a) 700°C

(b) 680°C

(c) 500°C

(d) 360°C.

**Q66. The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner ****surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be, the temperature at the outer surface of the wall would be**

(a) 700°C

(b) 680°C

(c) 40°C

(d) 360°C.

**Q67. Choose the correct statement**

(a) The film heat transfer co-efficient is property of the fluid.

(b) The thermal conductivity is not a property of material.

(c) A body which is black in colour is called black body.

(d) A body which reflects all radiations is called white body.

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**Q68. The vapour compression refrigerators are based on the principle that fluids absorb heat while changing from a**

(a) vapour phase to liquid phase and give up heat in changing from a liquid phase to vapour phase

(b) liquid phase to vapour phase and give up heat in changing from a vapour phase to liquid phase

(c) vapour phase to liquid phase only

(d) none of the above.

**Q69. The difference between vapour compression and vapour absorption refrigeration cycle is that**

(a) absorption cycle requires more work input

(b) absorption cycle requires less work input

(c) vapour compression cycle requires a pump

(d) none of the above.

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**Q70. The rate of heat flow through a composite wall of three layers of thickness 0.3 m, 0.2 m, 0.15 m and of corresponding thermal conductivities 0.3, 0.2 and 0.15 kcal/hr m°C is 320 kcal/hr. If the surface area normal to the direction of flow of heat is 1 m2 and inner ****surface temperature is 1000°C,then the interface temperature at the end of 1st layer will be**

(a) 700°C

(b) 680°C

(c) 500°C

(d) 360°C.

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**Read More Sections of Heat Transfer and Mass Transfer**

Each section contains maximum 80 Questions. To practice more questions visit other sections.

**Heat and Mass Transfer****, RAC MCQ** – Section-1

**Heat and Mass Transfer****, RAC MCQ** – Section-2

**Heat and Mass Transfer****, RAC MCQ** – Section-3

**Heat and Mass Transfer****, RAC MCQ** – Section-4