Home
Current Affairs January 2024

What is the correct answer?

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

Correct Answer :

B. Do not move actually


Related Questions

What is the correct answer?

4

The heat transfer by conduction through a thick sphere is given by

A. Q = 2πkr1 r2 (T1 - T2)/ (r2 - r1)

B. Q = 4πkr1 r2 (T1 - T2)/ (r2 - r1)

C. Q = 6πkr1 r2 (T1 - T2)/ (r2 - r1)

D. Q = 8πkr1 r2 (T1 - T2)/ (r2 - r1)

What is the correct answer?

4

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as

A. Conduction

B. Free convection

C. Forced convection

D. Radiation

What is the correct answer?

4

The insulation ability of an insulator with the presence of moisture would

A. Increase

B. Decrease

C. Remain unaffected

D. May increase/decrease depending on temperature and thickness of insulation

What is the correct answer?

4

Which of the following would lead to a reduction in thermal resistance?

A. In conduction, reduction in the thickness of the material and an increase in thermal conductivity.

B. In convection, stirring of the fluid and cleaning the heating surface.

C. In radiation, increasing the temperature and reducing the emissivity.

D. All of the above

What is the correct answer?

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

What is the correct answer?

4

Which of the following property of air does not increase with rise in temperature?

A. Thermal conductivity

B. Thermal diffusivity

C. Density

D. Dynamic viscosity

What is the correct answer?

4

Moisture would find its way into insulation by vapour pressure unless it is prevented by

A. High thickness of insulation

B. High vapour pressure

C. Less thermal conductivity insulator

D. A vapour seal

What is the correct answer?

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

What is the correct answer?

4

The critical temperature is the temperature

A. Below which a gas does not obey gas laws

B. Above which a gas may explode

C. Below which a gas is always liquefied

D. Above which a gas will never liquefied

What is the correct answer?

4

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

What is the correct answer?

4

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. Wien's law

B. Stefan's law

C. Kirchhoff's law

D. Planck's law

What is the correct answer?

4

Thermal conductivity of non-metallic amorphous solids with decrease in temperature

A. Increases

B. Decreases

C. Remain constant

D. May increase or decrease depending on temperature

What is the correct answer?

4

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)

What is the correct answer?

4

Stefan Boltzmann law is applicable for heat transfer by

A. Conduction

B. Convection

C. Radiation

D. Conduction and radiation combined

What is the correct answer?

4

A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100° C and leaves at 60° C. A cold fluid enters the heat exchanger at 40° C. The mean temperature difference between the two fluids is

A. 20°C

B. 40°C

C. 60°C

D. 66.7°C

What is the correct answer?

4

Depending on the radiating properties, body will be transparent when

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

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

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

D. X = 0, a + p = 1

What is the correct answer?

4

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.

What is the correct answer?

4

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

What is the correct answer?

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

What is the correct answer?

4

Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)

A. h = k/ ρS

B. h = ρS/k

C. h = S/ρk

D. h = kρ/S

What is the correct answer?

4

Heat transfer by radiation mainly depends upon

A. Its temperature

B. Nature of the body

C. Kind and extent of its surface

D. All of the above

What is the correct answer?

4

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.

What is the correct answer?

4

Which of the following has maximum value of thermal conductivity?

A. Aluminium

B. Steel

C. Brass

D. Copper

What is the correct answer?

4

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

What is the correct answer?

4

The use of heat exchangers is made in

A. Radiators in automobile

B. Condensers and boilers in steam plants

C. Condensers and evaporators in refrigeration and air conditioning units

D. All of the above

What is the correct answer?

4

According to Wien's law, the wavelength corresponding to maximum energy is proportion to

A. Absolute temperature (T)

B.

C. F

D. T

What is the correct answer?

4

Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by

A. Convection

B. Radiation

C. Forced convection

D. Free convection

What is the correct answer?

4

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

What is the correct answer?

4

Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be

A. One

B. Two

C. Three

D. Four

What is the correct answer?

4

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