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4

The heat transfer takes place according to

A. Zeroth law of thermodynamics

B. First law of thermodynamics

C. Second law of thermodynamics

D. Kirchhoff's law

Correct Answer :

C. Second law of thermodynamics


Related Questions

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4

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

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4

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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4

Fouling factor is used

A. In heat exchanger design as a safety factor

B. In case of Newtonian fluids

C. When a liquid exchanges heat with a gas

D. None of the above

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4

According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to

A. Absolute temperature

B. Square of temperature

C. Fourth power of absolute temperature

D. Fourth power of temperature

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4

Unit of thermal diffusivity is

A. m²/hr

B. m²/hr °C

C. kcal/m² hr

D. kcal/m. hr °C

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Thermal diffusivity of a substance is

A. Directly proportional to thermal conductivity

B. Inversely proportional to density of substance

C. Inversely proportional to specific heat

D. All of the above

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4

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

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4

The amount of heat flow through a body by conduction is

A. Directly proportional to the surface area of the body

B. Directly proportional to the temperature difference on the two faces of the body

C. Dependent upon the material of the body

D. All of the above

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4

LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is

A. Higher

B. Lower

C. Same

D. Depends on the area of heat exchanger

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4

Thermal conductivity of glass wool varies from sample to sample because of variation in

A. Composition

B. Density

C. Porosity

D. All of the above

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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 rate of energy emission from unit surface area through unit solid angle, along a normal to the surface, is known as

A. Emissivity

B. Transmissivity

C. Reflectivity

D. Intensity of radiation

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Depending on the radiating properties, a body will be white when

A. P = 0, x = 0 and a = 1

B. P=1, T = 0 and a = 0

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

D. X = 0, a + p = 1 Where a = absorptivity, p = reflectivity, x = transmissivity

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4

When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,

A. α = 1, ρ = 0 and τ = 0

B. α = 0, ρ = 1 and τ = 0

C. α = 0, ρ = 0 and τ = 1

D. α + ρ = 1 and τ = 0

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4

Thermal diffusivity of a substance is

A. Directly proportional to the thermal conductivity

B. Inversely proportional to density of substance

C. Inversely proportional to specific heat

D. All of the above

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4

Which of the following is the case of heat transfer by radiation?

A. Blast furnace

B. Heating of building

C. Cooling of parts in furnace

D. Heat received by a person from fireplace

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4

Thermal conductivity of water in general with rise in temperature

A. Increases

B. Decreases

C. Remain constant

D. May increase or decrease depending on temperature

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Two balls of same material and finish have their diameters in the ratio of 2: 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of

A. 1 : 1

B. 2 : 1

C. 1 : 2

D. 4 : 1

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The ratio of the energy absorbed by the body to total energy falling on it is called

A. Absorptive power

B. Emissive power

C. Absorptivity

D. Emissivity

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4

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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4

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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Temperature of steam at around 540°C can be measured by

A. Thermometer

B. Thermistor

C. Thermocouple

D. None of these

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4

Depending on the radiating properties, a body will be black when

A. P = 0, x = 0 and a = 1

B. P= 1, T = 0 and a = 0

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

D. X = 0, a + p = 0 Where a = absorptivity, p = reflectivity, X = transmissivity.

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Stefan Boltzmann law is applicable for heat transfer by

A. Conduction

B. Convection

C. Radiation

D. Conduction and radiation combined

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4

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

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Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

A. k. A. (dT/dx)

B. k. A. (dx/dT)

C. k. (dT/dx)

D. k. (dx/dT)

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The emissive power of a body depends upon its

A. Temperature

B. Wave length

C. Physical nature

D. All of the above

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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

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4

The process of heat transfer from one particle of the body to another is called conduction, when the particles of the body

A. Move actually

B. Do not move actually

C. Affect the intervening medium

D. Does not affect the intervening medium

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The concept of overall coefficient of heat transfer is used in heat transfer problems of

A. Conduction

B. Convection

C. Radiation

D. Conduction and convection