What is the thermal conductivity of a perfect heat insulator? (A) Zero (B) One (C) ∞ (D) Between 0 and ∞

What is the thermal conductivity of a perfect heat insulator?

(A) Zero

(B) One

(C) ∞

(D) Between 0 and ∞

by

1 Answer

Answer :

(A) Zero

by

Related questions

Absorptivity and reflectivity of a perfect black body are respectively (A) 1 and 0 (B) 0 and 1 (C) 1 and ∞ (D) 0 and 0.5

Description : Absorptivity and reflectivity of a perfect black body are respectively (A) 1 and 0 (B) 0 and 1 (C) 1 and ∞ (D) 0 and 0.5

Last Answer : (A) 1 and 0

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2 . The temperature of the inside wall is - 5°C. The outside wall temperature is (A) 25°C (B) 30°C (C) 35°C (D) 40°C

Description : The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2 . The temperature of the inside wall is - 5°C. The outside wall temperature is (A) 25°C (B) 30°C (C) 35°C (D) 40°C

Last Answer : (C) 35°C

A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Description : A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Last Answer : (B) 0.025

The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2 .K. At steady state, the temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Description : The left face of a one dimensional slab of thickness 0.2 m is maintained at 80°C and the right face is exposed to air at 30°C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the ... temperature of the right face in °C is (A) 77.2 (B) 71.2 (C) 63.8 (D) 48.7

Last Answer : (D) 48.7

A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness __________ metre. (A) 0.01 (B) 0.1 (C) 0.25 (D) 0.5

Description : A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of ... and thickness __________ metre. (A) 0.01 (B) 0.1 (C) 0.25 (D) 0.5

Last Answer : (B) 0.1

What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Last Answer : (A) 2

One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is (A) 100 (B) 900 (C) 9000 (D) 10000

Description : One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is (A) 100 (B) 900 (C) 9000 (D) 10000

Last Answer : (D) 10000

Graphite is a good (A) Thermal & electrical insulator (B) Conductor of heat (C) Conductor of electricity (D) Both (B) & (C)

Description : Graphite is a good (A) Thermal & electrical insulator (B) Conductor of heat (C) Conductor of electricity (D) Both (B) & (C)

Last Answer : (D) Both (B) & (C)

For a perfect dielectric, which parameter will be zero? a) Conductivity b) Frequency c) Permittivity d) Permeability

Description : For a perfect dielectric, which parameter will be zero? a) Conductivity b) Frequency c) Permittivity d) Permeability

Last Answer : a) Conductivity

Pick out the wrong statement. (A) Reciprocal of the resistance to heat flow is called thermal conductance (B) Unit of thermal conductance is W/°K (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A (D) None of these

Description : Pick out the wrong statement. (A) Reciprocal of the resistance to heat flow is called thermal conductance (B) Unit of thermal conductance is W/°K (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A (D) None of these

Last Answer : (C) Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A

Heat transfer occurs by natural convection because change in temperature causes difference in (A) Viscosity (B) Density (C) Thermal conductivity (D) Heat capacity

Description : Heat transfer occurs by natural convection because change in temperature causes difference in (A) Viscosity (B) Density (C) Thermal conductivity (D) Heat capacity

Last Answer : (B) Density

The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Description : The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K

Last Answer : (B) 2K/h0

Low thermal conductivity of heat insulating materials is due to its (A) Dense structure (B) High proportion of air space (C) High specific heat (D) None of these

Description : Low thermal conductivity of heat insulating materials is due to its (A) Dense structure (B) High proportion of air space (C) High specific heat (D) None of these

Last Answer : (B) High proportion of air space

Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Description : Heat transfer rate per unit area is called (A) Thermal conductivity (B) Heat flux (C) Heat transfer co-efficient (D) Thermal diffusivity

Last Answer : (B) Heat flux

Heat transfer rate described by Fourier's law will decrease, if the __________ increases. (A) Thermal conductivity (B) Thickness (C) Temperature difference (D) Heat transfer area

Description : Heat transfer rate described by Fourier's law will decrease, if the __________ increases. (A) Thermal conductivity (B) Thickness (C) Temperature difference (D) Heat transfer area

Last Answer : (B) Thickness

Finned tube heat exchangers (A) Give larger area per tube (B) Use metal fins of low thermal conductivity (C) Facilitate very large temperature drop through tube wall (D) Are used for smaller heat load

Description : Finned tube heat exchangers (A) Give larger area per tube (B) Use metal fins of low thermal conductivity (C) Facilitate very large temperature drop through tube wall (D) Are used for smaller heat load

Last Answer : (A) Give larger area per tube

In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Description : In Fourier's law, the proportionality constant is called the (A) Heat transfer co-efficient (B) Thermal diffusivity (C) Thermal conductivity (D) Stefan-Boltzmann constant

Last Answer : (C) Thermal conductivity

Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.) (A) x/KA (B) KA/x (C) K/Ax (D) A/Kx

Description : Conductance is given by (where, x = thickness, A = heat flow area, K = thermal conductivity.) (A) x/KA (B) KA/x (C) K/Ax (D) A/Kx

Last Answer : (B) KA/x

Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity (C) In unsteady state heat conduction, heat flows in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Description : Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the ... in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

Last Answer : (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is ‘3k/l’. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?(A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Description : Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l'. If the wall temperature ... wall temperature in degree centigrade? (A) 35.5 (B) 43.75 (C) 81.25 (D) 48.25

Last Answer : (C) 81.25

In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the (A) Rate of firing and emissivity of flame (B) Thermal conductivity of the charge & structural materials of furnace (C) Nature of process; whether batch, continuous or intermittent (D) All (A), (B) and (C)

Description : In a furnace, the heat taken by the charge/stock and the heat lost to the furnace structure & flue gases depends on the (A) Rate of firing and emissivity of flame (B) Thermal conductivity of the charge & ... (C) Nature of process; whether batch, continuous or intermittent (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

ick out the undesirable property for a good refrigerant. (A) High thermal conductivity (B) Low freezing point (C) Large latent heat of vaporisation (D) High viscosity

Description : ick out the undesirable property for a good refrigerant. (A) High thermal conductivity (B) Low freezing point (C) Large latent heat of vaporisation (D) High viscosity

Last Answer : (D) High viscosity

Heat required to raise the temperature of a body by 1 °C is called its (A) Heat capacity (B) Specific heat capacity (C) Thermal conductivity (D) Water equivalent

Description : Heat required to raise the temperature of a body by 1 °C is called its (A) Heat capacity (B) Specific heat capacity (C) Thermal conductivity (D) Water equivalent

Last Answer : (A) Heat capacity

Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Description : Nusselt number/Biot number varies (A) Inversely with thermal conductivity (B) Directly with heat transfer co-efficient (C) Directly with thermal conductivity (D) Inversely with the dimension of the solid

Last Answer : (A) Inversely with thermal conductivity

reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity (C) Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Description : reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by ... Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

Last Answer : Option C

ideal material for making cooking vessels should have (A) High heat capacity (B) Low heat capacity (C) High thermal conductivity (D) Both (B) and (C)

Description : ideal material for making cooking vessels should have (A) High heat capacity (B) Low heat capacity (C) High thermal conductivity (D) Both (B) and (C)

Last Answer : Option D

The ratio of volume of mixed reactor to the volume of P.F.R. (for identical flow rate, feed composition and conversion) for zero order reaction is: (A) ∞(B) 0 (C) 1 (D) > 1

Description : The ratio of volume of mixed reactor to the volume of P.F.R. (for identical flow rate, feed composition and conversion) for zero order reaction is: (A) ∞ (B) 0 (C) 1 (D) > 1

Last Answer : (C) 1

If electrical conductivity increases with the increase of temperature of a substance, then it is a: (1) Conductor (2) Semiconductor (3) Insulator (4) Carborator

Description : If electrical conductivity increases with the increase of temperature of a substance, then it is a: (1) Conductor (2) Semiconductor (3) Insulator (4) Carborator

Last Answer : (2) Semiconductor Explanation: A solid substance that has conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects

If electrical conductivity increases with the increase of temperature of a substance, then it is a (1) Conductor (2) Semiconductor (3) Insulator (4) Carborator

Description : If electrical conductivity increases with the increase of temperature of a substance, then it is a (1) Conductor (2) Semiconductor (3) Insulator (4) Carborator

Last Answer : (2) Semiconductor Explanation: A solid substance that has conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects.

A semiconductor is a material with a _____________. A. conductivity higher than a normal conductor B. conductivity higher than a normal insulator C. high conductivity at low temperatures D. low conductivity at high temperatures

Description : A semiconductor is a material with a _____________. A. conductivity higher than a normal conductor B. conductivity higher than a normal insulator C. high conductivity at low temperatures D. low conductivity at high temperatures

Last Answer : Answer: B

Which solid material has a high heat capacity but low thermal conductivity?

Description : Which solid material has a high heat capacity but low thermal conductivity?

Last Answer : https://en.wikipedia.org/wiki/Thermal_barrier_coating

On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because – (1) metals have higher thermal capacity than plastics (2) plastics have a lower density than metals (3) metals are good conductors of heat (4) plastics have a higher thermal conductivity than metals

Description : On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because - (1) metals ... metals (3) metals are good conductors of heat (4) plastics have a higher thermal conductivity than metals

Last Answer : (3) metals are good conductors of heat Explanation: On a chilly day, the room temperature is lower than our body temperature. Since metals have a higher coefficient of thermal conductivity than plastic, they ... from our fingers will flow to the metal cap much more quickly than to the plastic body.

Which of the following criterion is used for any metal to be used as a cooking material? (1) More specific heat (2) More thermal conductivity (3) Less thermal conductivity (4) Less electrical conductivity

Description : Which of the following criterion is used for any metal to be used as a cooking material? (1) More specific heat (2) More thermal conductivity (3) Less thermal conductivity (4) Less electrical conductivity

Last Answer : (3) Less thermal conductivity Explanation: A metal to be used as a cooking material should have less thermal conductivity.

What is a measure of the ability of a material to conduct heat?  A. Specific heat capacity  B. Coefficient of thermal expansion  C. Coefficient of thermal conductivity  D. Thermal conductivity

Description : What is a measure of the ability of a material to conduct heat?  A. Specific heat capacity  B. Coefficient of thermal expansion  C. Coefficient of thermal conductivity  D. Thermal conductivity

Last Answer : Thermal conductivity

Which of the following items is not a path function  (a) heat  (b) work  (c) kinetic energy  (d) vdp  (e) thermal conductivity.

Description : Which of the following items is not a path function  (a) heat  (b) work  (c) kinetic energy  (d) vdp  (e) thermal conductivity.

Last Answer : Answer : e

On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because : (1) metals have higher thermal capacity than plastics (2) plastics have a lower density than metals (3) metals are good conductors of heat (4) plastics have a higher thermal conductivity than metals

Description : On a cold day when the room temperature is 15°C, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15°C, because : (1) metals ... metals (3) metals are good conductors of heat (4) plastics have a higher thermal conductivity than metals

Last Answer : metals are good conductors of heat

Which of the following criterion is used for any metal to be used as a cooking material ? (1) More specific heat (2) More thermal conductivity (3) Less thermal conductivity (4) Less electrical conductivity

Description : Which of the following criterion is used for any metal to be used as a cooking material ? (1) More specific heat (2) More thermal conductivity (3) Less thermal conductivity (4) Less electrical conductivity

Last Answer : Less thermal conductivity 

In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is (A) ∞ (B) 0 (C) Equal to the difference between hot and cold fluids inlet temperature (D) Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

Description : In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is (A) ∞ (B) 0 ... temperature (D) Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature

Last Answer : (B) 0

The specific heat of saturated water vapour at 100°C is (A) ∞ (B) -ve (C) 0 (D) +ve

Description : The specific heat of saturated water vapour at 100°C is (A) ∞ (B) -ve (C) 0 (D) +ve

Last Answer : B) -ve

Molar heat capacity of water in equilibrium with ice at constant pressure is __________ Kcal/kg mole. °K (A) 0 (B) ∞ (C) 50 (D) 100

Description : Molar heat capacity of water in equilibrium with ice at constant pressure is __________ Kcal/kg mole. °K (A) 0 (B) ∞ (C) 50 (D) 100

Last Answer : (B) ∞

When the rotational path of the magnetic field intensity is zero, then the current in the path will be a) 1 b) 0 c) ∞ d) 0.5

Description : When the rotational path of the magnetic field intensity is zero, then the current in the path will be a) 1 b) 0 c) ∞ d) 0.5

Last Answer : b) 0

The driving point impedance with poles at ω = 0(zero) and ω = ∞ (infinity) must have the

Description : The driving point impedance with poles at ω = 0(zero) and ω = ∞ (infinity) must have the  (a) s term in the denominator and an excess term in the numerator (b) s term in the ... the numerator and denominator (d) s term in the denominator and equal number of terms in the numerator and denominator

Last Answer : The driving point impedance with poles at ω = 0(zero) and ω = ∞ (infinity) must have the s term in the denominator and an excess term in the numerator

In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always (A) < 1 (B) > 1 (C) 1 (D) ∞

Description : In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always (A) < 1 (B) > 1 (C) 1 (D) ∞

Last Answer : (A) < 1

In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C. (A) 20 (B) 60 (C) 120 (D) ∞

Description : In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is __________ °C. (A) 20 (B) 60 (C) 120 (D) ∞

Last Answer : (D) ∞

A perfect gas (A) Does not satisfy PV = nRT (B) Is incompressible and has zero viscosity (C) Has constant specific heat (D) Can’t develop shear stresses

Description : A perfect gas (A) Does not satisfy PV = nRT (B) Is incompressible and has zero viscosity (C) Has constant specific heat (D) Can’t develop shear stresses

Last Answer : (C) Has constant specific heat

When a material has zero permittivity, the maximum potential that it can possess is a) ∞ b) -∞ c) Unity d) Zero

Description : When a material has zero permittivity, the maximum potential that it can possess is a) ∞ b) -∞ c) Unity d) Zero

Last Answer : d) Zero

For a test charge placed at infinity, the electric field will be a) Unity b) +∞ c) Zero d) -∞

Description : For a test charge placed at infinity, the electric field will be a) Unity b) +∞ c) Zero d) -∞

Last Answer : c) Zero

Power consumption during turbulent flow in agitation tank is proportional to the __________ of the liquid. (A) Viscosity (B) Thermal conductivity(C) Surface tension(D) Density

Description : Power consumption during turbulent flow in agitation tank is proportional to the __________ of the liquid. (A) Viscosity (B) Thermal conductivity (C) Surface tension (D) Density

Last Answer : (D) Density

Copper has very low (A) Malleability (B) Ductility (C) Tensile strength (D) Thermal & electrical conductivity

Description : Copper has very low (A) Malleability (B) Ductility (C) Tensile strength (D) Thermal & electrical conductivity

Last Answer : (C) Tensile strength

Coke oven regenerators are made of __________ bricks. (A) Fire clay (B) Silica (C) Low thermal conductivity (D) High electrical conductivity

Description : Coke oven regenerators are made of __________ bricks. (A) Fire clay (B) Silica (C) Low thermal conductivity (D) High electrical conductivity

Last Answer : (A) Fire clay