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Which of the following is expected to have highest thermal conductivity?

A. Steam

B. Solid ice

C. Melting ice

D. Water

Correct Answer :

B. Solid ice


Related Questions

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In regenerator type heat exchanger, heat transfer takes place by

A. Direct mixing of hot and cold fluids

B. A complete separation between hot and cold fluids

C. Flow of hot and cold fluids alternately over a surface

D. Generation of heat again and again

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4

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

Which of the following is a case of steady state heat transfer?

A. I.C. engine

B. Air preheaters

C. Heating of building in winter

D. None of the above

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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

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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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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

The critical thickness of insulation for a sphere is

A. k/h₀

B. 2k/h₀

C. h₀/k

D. h₀/2k

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4

The highest thermal diffusivity is of

A. Iron

B. Lead

C. Concrete

D. Wood

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Which of the following statement is correct?

A. A grey body is one which absorbs all radiations incident on it.

B. At thermal equilibrium, the emissivity and absorptivity are same.

C. The energy absorbed by a body to the total energy falling on it, is called emissivity.

D. A perfect body is one which is black in colour.

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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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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

The value of the wave length for maximum emissive power is given by

A. Kirchhoff's law

B. Stefan's law

C. Wines law

D. Planck's law

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A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,

A. The better insulation must be put inside

B. The better insulation must be put outside

C. One could place either insulation on either side

D. One should take into account the steam temperature before deciding as to which insulation is put where

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When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred as heat transfer by

A. Conduction

B. Convection

C. Radiation

D. Conduction and convection

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In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by

A. Convection

B. Radiation

C. Conduction

D. Both convection and conduction

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Which of the following has least value of conductivity?

A. Glass

B. Water

C. Plastic

D. Air

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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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Unit of thermal conductivity in S.I. units is

A. J/m² sec

B. J/m °K sec

C. W/m °K

D. Option (B) and (C) above

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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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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

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In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

A. Reynold's number

B. Grashoff's number

C. Reynold's number, Grashoff's number

D. Prandtl number, Grashoff's number

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

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

B. P=1, x = 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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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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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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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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Which of the following is expected to have highest thermal conductivity?

A. Steam

B. Solid ice

C. Melting ice

D. Water

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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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All radiations in a black body are

A. Reflected

B. Refracted

C. Transmitted

D. Absorbed

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An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be

A. 25 mm

B. 40 mm

C. 160 mm

D. 800 mm

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The transfer of heat by molecular collision is smallest in

A. Solids

B. Liquids

C. Gases

D. None of these