Description : With increase in temperature, the thermal conductivity of steel (A) Increases (B) Decreases (C) Remains unchanged (D) Increases exponentially
Last Answer : (B) Decreases
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
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
Description : Which of the following has the minimum thermal conductivity? (A) Nitrogen (B) Steel (C) Carbon black
Last Answer : (A) Nitrogen
Description : Which of the following commonly used condenser tube materials has the lowest thermal conductivity? (A) Admiralty brass (B) Stainless steel (C) Aluminium brass (D) Titanium
Last Answer : (B) Stainless steel
Description : A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature ... difference across the layer A is __________ °C. (A) 6 (B) 12 (C) 18 (D) 24
Last Answer : (B) 12
Description : With increase in temperature, the thermal conductivity of most liquids (A) Increases (B) Decreases (C) Remain same (D) First increases upto a certain temperature and then becomes constant
Last Answer : (C) Remain same
Description : With increase in temperature, the thermal conductivity of a gas (A) Increases (B) Decreases (C) Remain same (D) May increase or decrease depending on the type of gas
Last Answer : (A) Increases
Description : The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K) (A) T (B) 1/T (C) T2 (D) 1/T2
Last Answer : A) T
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
Description : Which of the following has maximum thermal conductivity? (A) Iron (B) Coal (C) Nitrogen
Last Answer : (A) Iron
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.
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
Description : Which of the following has the highest thermal conductivity? (A) Brick (B) Air (C) Water (D) Silver
Last Answer : (D) Silver
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
Description : With increase in temperature, the rate of leaching increases, because the (A) Diffusivity of solute increases (B) Viscosity of solvent decreases (C) Thermal conductivity of solute increases (D) None of these
Last Answer : (A) Diffusivity of solute increases
Description : If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ ... (A) Hyperbolic (B) Parabolic (C) Linear (D) Logarithmic
Last Answer : (C) Linear
Description : __________ equation relates the thermal conductivity of a solid to its temperature. (A) Antoine (B) Kopp's (C) Lee's (D) Kistyakowsky
Last Answer : (C) Lee's
Description : For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally (A) Decreases (B) Increases (C) Remains unchanged (D) Increases exponentially
Last Answer : (A) Decreases
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
Description : Thermal conductivity of a conducting solid material depends upon its (A) Temperature (B) Porosity (C) Both (A) & (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) & (B)
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
Description : The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in °K). The units of 'a' in SI system will be (A) W/m.k (B) W/m (C) W/m.k
Last Answer : (C) W/m.k
Description : With increase in temperature, the thermal conductivity of non-metallic amorphous solids (A) Decreases (B) Increases (C) Remain constant (D) First decreases upto certain temperature and then increases
Last Answer : (B) Increases
Description : A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature ... drop (in °K) across the layer of material 'A' is (A) 125 (B) 133 (C) 150 (D) 160
Last Answer : (D) 160
Description : With increase in temperature, the thermal conductivity of fresh lubricating oil (A) Increases (B) Decreases (C) Remains unchanged (D) May increase or decrease; depends on its composition
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
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
Description : If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law. (A) Parabolic (B) Hyperbolic (C) Linear (D) Logarithmic
Last Answer : (A) Parabolic
Description : Thermal conductivity of a gas at low density, __________ with increase in temperature. (A) Decreases (B) Increases (C) Remains unchanged (D) May increase or decrease; depends on the gas
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
Description : Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. °C respectively are joined together. The temperature outside of A and C are 30°C and 100°C respectively. The interface ... C will be at a temperature of __________ °C. (A) 40 (B) 95 (C) 70 (D) 50
Last Answer : (C) 70
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
Description : Which of the following variables affects the furnace capacity? (A) Temperature of flue gas (B) Thermal conductivity of stock (C) Thickness of heating stock (D) All (A), (B) and (C)
Last Answer : (D) All (A), (B) and (C)
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
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
Description : Pick out the wrong statement. (A) Higher temperature is employed in visbreaking than in thermal cracking (B) Pyrolysis is a mild thermal cracking process (C) Lead susceptibility of ... Operating pressure and temperature in thermal cracking process is more than that in catalytic cracking process
Last Answer : (A) Higher temperature is employed in visbreaking than in thermal cracking (B) Pyrolysis is a mild thermal cracking process
Description : Which °fine metals has the maximum thermal conductivity? (1) Iron (2) Aluminium (3) Silver (4) Copper
Last Answer : (3) Silver Explanation: Silver has the best thermal conductivity of 429 W/mK at RT (295K). It is followed by copper, gold and aluminium. Metals generally have very good electrical conductivity, that leads to high thermal conductivity.
Description : Which of the metals has the maximum thermal conductivity? (1) Iron (2) Aluminium (3) Silver (4) Copper
Last Answer : Silver
Description : Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water. (A) Boiling point (at the same pressure) (B) Viscosity (C) Density (D) Thermal conductivity
Last Answer : (A) Boiling point (at the same pressure)
Description : Maximum soot is released from (A) Petrol vehicles (B) CNG vehicles (C) Diesel vehicles (D) Thermal Power Plants
Last Answer : (D) Thermal Power Plants
Description : The thermal conductivity of hydrogen is ______ times that of air (a) 2 (b) 3 (c) 5 (d) 7
Last Answer : (d) 7
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
Description : Copper has very low (A) Malleability (B) Ductility (C) Tensile strength (D) Thermal & electrical conductivity
Last Answer : (C) Tensile strength
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
Description : A bearing metal should not have (A) Enough plasticity (B) Low thermal conductivity (C) Low co-efficient of friction (D) High toughness
Last Answer : (B) Low thermal conductivity
Description : Coke oven walls are lined with __________ bricks. (A) Silica (B) Tar-dolomite (C) Low thermal conductivity (D) Fire clay
Last Answer : (A) Silica
Description : Brass tubes are used in the manufacture of tubes of evaporators used in sugar and salt industries, mainly because of its (A) High co-efficient of thermal expansion (B) Low thermal conductivity (C) High corrosion resistance (D) All (A), (B) and (C)
Last Answer : (C) High corrosion resistance
Description : Tin base and lead base alloys are used for bearing materials. Tin compared to lead has lower (A) Price (B) Corrosion resistance (C) Thermal conductivity (D) Abundant availability
Last Answer : (D) Abundant availability
Description : Pick out the wrong statement. (A) Pure rubber is as useless as pure gold as a material of construction (B) Thermal conductivity of aluminium is higher than that of copper; henceit is ... has poor weldability (D) Reinforced plastics are made from both thermoplastic as well as thermosetting plastics
Last Answer : (B) Thermal conductivity of aluminium is higher than that of copper; henceit is increasingly used for utensil making