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The radiation emitted by a black body is known as

A. Black radiation

B. Full radiation

C. Total radiation

D. All of these

Correct Answer :

D. All of these


Related Questions

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Which of the following has maximum value of thermal conductivity?

A. Aluminium

B. Steel

C. Brass

D. Copper

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Pick up the wrong case. Heat flowing from one side to other depends directly on

A. Face area

B. Time

C. Thickness

D. Temperature difference

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Absorptivity of a body will be equal to its emissivity

A. At all temperatures

B. At one particular temperature

C. When system is under thermal equilibrium

D. At critical temperature

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Wiens 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

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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)

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In a shell and tube heat exchanger, baffles are provided on the shell side to

A. Improve heat transfer

B. Provide support for tubes

C. Prevent stagnation of shell side fluid

D. All of these

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In counter flow heat exchangers

A. Both the fluids at inlet (of heat exchanger where hot fluid enters) are in their coldest state

B. Both the fluids at inlet are in their hottest state

C. Both the fluids at exit are in their hottest state

D. One fluid is in hottest state and other in coldest state at inlet

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The natural convection air cooled condensers are used in

A. Domestic refrigerators

B. Water coolers

C. Room air conditioners

D. All of these

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Metals are good conductors of heat because

A. Their atoms collide frequently

B. Their atoms are relatively far apart

C. They contain free electrons

D. They have high density

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All radiations in a black body are

A. Reflected

B. Refracted

C. Transmitted

D. Absorbed

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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

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Film coefficient is defined as Inside diameter of tube

A. Equivalent thickness of film

B. Thermal conductivity Equivalent thickness of film Specific heat × Viscosity

C. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity

D. Film coefficient × Inside diameter Thermal conductivity

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The unit of overall coefficient of heat transfer is

A. kcal/m²

B. kcal/hr °C

C. kcal/m² hr °C

D. kcal/m hr °C

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Kirchhoff's law states that

A. The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature

B. The wave length corresponding to the maximum energy is proportional to the absolute temperature

C. 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

D. None of the above

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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

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Fourier's law of heat conduction is valid for

A. One dimensional cases only

B. Two dimensional cases only

C. Three dimensional cases only

D. Regular surfaces having non-uniform temperature gradients

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According to Stefan's law, the total radiation from a black body per second per unit area is proportional to

A. Absolute temperature

B.

C. T⁵

D. T

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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

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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

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The process of heat transfer from one particle of the body to another by the actual motion of the heated particles, is called

A. Conduction

B. Convection

C. Radiation

D. None of these

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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

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The unit of Stefan-Boltzmann constant is

A. Watt/mK

B. Watt/m²K²

C. Watt/m²K4

D. Watt/mK²

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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. Kirchoffs law

B. Stefan's law

C. Wien' law

D. Planck's law

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Heat is closely related with

A. Liquids

B. Energy

C. Temperature

D. Entropy

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The thickness of thermal and hydrodynamic boundary layer is equal if Prandtl number is

A. Equal to one

B. Greater than one

C. Less than one

D. Equal to Nusselt number

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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

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Heat transfer in liquid and gases takes place by

A. Conduction

B. Convection

C. Radiation

D. Conduction and convection

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Fourier's law of heat conduction gives the heat flow for

A. Irregular surfaces

B. Nonuniform temperature surfaces

C. One dimensional cases only

D. Two dimensional cases only

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Which of the following statement is wrong?

A. The heat transfer in liquid and gases takes place according to convection.

B. The amount of heat flow through a body is dependent upon the material of the body.

C. The thermal conductivity of solid metals increases with rise in temperature

D. Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference.

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Unit of thermal conductivity in M.K.S. units is

A. K cal/kg m² °C

B. K cal m/hr m² °C

C. K cal/hr m² °C

D. K calm/hr °C