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- Heat Transfer Questions - Set 5
MCQs 1: Which of the following sentences are correct for black body (1) The black body is a hypothetical body (2) The black body is a real body (3) The black body is used as a standard of perfection against which the radiation characteristics of other bodies are compared
sentences (1) and (2)
sentences (1) and (3)
sentences (2) and (3)
all the sentences (1), (2) and (3)
MCQs 2: What is the relation between emissive power of a real body (E) and emissive power of black body (Eb) when both are at same temperature? Where, α =absorptivity
MCQs 3: The emissivity (ε) can be defined as the ratio of
emissive power of real body to the emissive power of black body
emissive power of black body to the emissive power of real body
reflectivity of real body to emissive power of black body
reflectivity of black body to emissive power of real body
MCQs 4: What does the Kirchoff's identity state?
the emissivity and the absorptivity of the black body are same and always less than 1
the emissivity and the absorptivity of the black body are same and always more than 1
the emissivity and the absorptivity of the black body are same and always equal to 1
none of the above
MCQs 5: Stefan-Boltzmann law states that the energy radiated per unit area per unit time by the black body is
directly proportional to the square of the temperature of the black body
inversely proportional to the square of the temperature of the black body
directly proportional to the forth power of the temperature of the black body
inversely proportional to the fourth power of the temperature of the black body
MCQs 6: Which among the following sentences are correct for Stefan-Boltzmann law? (1) The Stefan-Boltzmann law gives the total emissive power of a black body. (2) The Stefan-Boltzmann law is based on quantum theory (3) The Stefan-Boltzmann law does not provide distribution of energy among different wavelengths
sentences (1) and (2) are correct
sentences (2) and (3) are correct
sentences (1) and (3) are correct
all of the sentences (1), (2) and (3) are correct
MCQs 7: The relation derived for the total emissive power of the black body as a function of wavelength and based of quantum theory is known as
MCQs 8: Which of the following is/are example/s of pool boiling?
completely submerged electrically heated coil in pool of liquid
boiling of liquid in a kettle placed on stove
both a. and b.
none of the above
MCQs 9: In pool boiling, as soon as the temperature of heating surface reaches the boiling point of the liquid, heat transfer takes place
MCQs 10: In pool boiling process, the region after the natural convection in which the vapour bubbles form with increase in heat flux, is called as
MCQs 11: When the formation of bubbles becomes very high in pool boiling, then the heat flux
MCQs 12: What is critical heat flux in boiling heat transfer process?
the heat flux which reaches at a certain constant value at a particular excess temperature
the heat flux which reaches at the minimum value at a particular excess temperature
the heat flux which reaches at the maximum value at a particular excess temperature
none of the above
MCQs 13: Consider the heat is transferred through a wall of surface area A and thickness t at the rate of q, what is the thermal resistance of the system? The thermal conductivity of the wall is k and the heat is transferred normal to the surface area A.
MCQs 14: The potential difference in an electrical system, is analogously considered as
a temperature difference in the heat transfer system
a current flow in the heat transfer system
a resistance in the heat transfer system
none of the above
MCQs 15: What is the correct formula for the rate of heat transfer (q) through a plane wall of thickness l and surface are A, when temperature difference between two surfaces is ΔT ? The thermal conductivity is k.
MCQs 16: Thermal conductivity of the same material varies with
the thickness of the material
the temperature of the material
both a. and b.
thermal conductivity of the same martial does not vary at all
MCQs 17: How does the thermal conductivity of a material change with respect to change in temperature of the same material?
thermal conductivity of a material increases with increase in its temperature
thermal conductivity of a material decreases with increase in its temperature
thermal conductivity of a material remains same with change in its temperature
unpredictable
MCQs 18: What does a composite wall mean?
two walls of different materials are connected in series without any gap between them
three walls of different materials are connected in series without any gap between them
more than three walls of different materials are connected in series without any gap between them
all of the above
MCQs 19: When a composite wall of three layers in series having thermal resistances R1, R2 and R3 respectively, the heat transfer takes place normal to the surface of the layers. How is the total thermal resistance of the composite system calculated?
MCQs 20: Why is the Buckingham π–Theorem used?
to determine number of dependent dimensionless groups which are necessary to represent the phenomenon in a mathematical expression
to determine number of independent dimensionless groups which are necessary to represent the phenomenon in a mathematical expression
to determine number of dependent groups with their dimensions which are necessary to represent the phenomenon in a mathematical expression
to determine number of independent groups with their dimensions which are necessary to represent the phenomenon in a mathematical expression
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