A __________ surface has the maximum thermal emissivity out of the following. (A) Black & smooth (B) Black & rough (C) White & smooth (D) White & rough

A __________ surface has the maximum thermal emissivity out of the

following.

(A) Black & smooth

(B) Black & rough

(C) White & smooth

(D) White & rough

by

1 Answer

Answer :

(B) Black & rough

by

Related questions

Which of the following is not a characteristic observed in material failure by fatigue fracture? (A) Plastic deformation of material does not occur (B) Initiation of crack from below the surface does not occur (C) Initiation of crack occurs on the surface of the machine part (D) Presence of both rough & smooth zone with conchoidal markings in smooth zone of the surface

Description : Which of the following is not a characteristic observed in material failure by fatigue fracture? (A) Plastic deformation of material does not occur (B) Initiation of crack from below the surface does ... (D) Presence of both rough & smooth zone with conchoidal markings in smooth zone of the surface

Last Answer : Option B

The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by (A) Painting the surface black (B) Painting the surface white (with aluminium paint) (C) Giving the surface a mirror finish (D) Roughening the surface

Description : The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by (A) Painting the surface black (B) ... white (with aluminium paint) (C) Giving the surface a mirror finish (D) Roughening the surface

Last Answer : (B) Painting the surface white (with aluminium paint)

A body absorbs heat most if it is – (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth

Description : A body absorbs heat most if it is – (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth

Last Answer : (1) black and rough Explanation: A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. Another property is roughness. Sand is rough and black and so it is a good absorber.

A body absorbs heat most if it is (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth

Description : A body absorbs heat most if it is (1) black and rough (2) black and smooth (3) white and rough (4) white and smooth

Last Answer : black and rough

The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2 . The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 × 10 -8 W/m2 .K4 )(A) 1000(B) 727(C) 800(D) 1200

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Last Answer : (A) 1000

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

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Last Answer : Option C

In thermal radiation for a black body (where, ε is emissivity and α is absorptivity) (A) α = 1; ε ≠ 1 (B) α ≠ 1, ε = 1 (C) α ≠ 1, ε ≠ 1 (D) α = 1; ε = 1

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Last Answer : (D) α = 1; ε = 1

A hot body will radiate heat most rapidly, if its surface is (A) White & rough (B) Black & rough (C) White & polished (D) Black & polished

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Last Answer : (B) Black & rough

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)

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

Consider two pipes of same length and diameter through which water is passed at the same velocity. The friction factor for rough pipe is f1 and that for smooth pipe is f2 . Pick out the correct statement(A) f1 = f2 (B) f1 < f2 (C) f1 > f2 (D) Data not sufficient to relate f1 & f2

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Last Answer : (C) f1 > f2

In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of (A) Relative roughness (B) Absolute roughness (C) Friction co-efficient for flows at equal Reynold number (D) All (A), (B) & (C)

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Last Answer : (C) Friction co-efficient for flows at equal Reynold number

In the equation of virtual work, following force is neglected (A) Reaction of any smooth surface with which the body is in contact (B) Reaction of a rough surface of a body which rolls on it without slipping (C) Reaction at a point or an axis, fixed in space, around which a body is constrained to turn (D) All of the above

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Last Answer : (D) All of the above

Pick up the correct statement from the following: (A) According to the petrological characteristics, concrete aggregates are classified as heavy weight, normal weight and light weight (B) According to the shape of the particles, concrete aggregates are classified as rounded irregular, angular and flaky (C) According to the surface texture of the particles, the concrete aggregates are classified as glassy, smooth, granular, rough, crystalline, honey combed and porous (D) All the above

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Last Answer : Answer: Option D

The term dispersion describes the process of ∙ A. separating light into its component frequencies ∙ B. reflecting light from a smooth surface ∙ C. the process by which light is absorbed by an uneven rough surface ∙ D. light scattering

Description : The term dispersion describes the process of ∙ A. separating light into its component frequencies ∙ B. reflecting light from a smooth surface ∙ C. the process by which light is absorbed by an uneven rough surface ∙ D. light scattering

Last Answer : A. separating light into its component frequencies

The termdispersion describestheprocessof a.separatinglightinto its componentfrequencies b. reflecting light from a smooth surface c. the process by which light is absorbed by an uneven rough surface d. light scattering

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Last Answer : a.separatinglightinto its componentfrequencies

Why do you polish the teeth before seating of a partial denture: A. To smooth the rough surface B. To minimise the retention of plaque C. To increase the adoptability of occlusal rests

Description : Why do you polish the teeth before seating of a partial denture: A. To smooth the rough surface B. To minimise the retention of plaque C. To increase the adoptability of occlusal rests

Last Answer : B. To minimise the retention of plaque

The heating capacity of muffle furnace depends on the (A) Surface area & emissivity of the stock (B) Properties of the muffle wall (temperature, area, and emissivity) (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : The heating capacity of muffle furnace depends on the (A) Surface area & emissivity of the stock (B) Properties of the muffle wall (temperature, area, and emissivity) (C) Both (A) & (B) (D) Neither (A) nor (B)

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

Which of the following parameters is not responsible for the heat loss from a hot steam carrying bare pipe surface located in a room without fans? (A) Emissivity of pipe surface (B) Diameter & length of the pipe (C) Temperature of hot pipe surface & that of air in the room (D) None of thes

Description : Which of the following parameters is not responsible for the heat loss from a hot steam carrying bare pipe surface located in a room without fans? (A) Emissivity of pipe surface (B) Diameter & length of the pipe (C) Temperature of hot pipe surface & that of air in the room (D) None of thes

Last Answer : Option D

The absorptivity of a body is equal to its emissivity (A) At a particular temperature (B) For circular bodies (C) Under thermal equilibrium (D) None of these

Description : The absorptivity of a body is equal to its emissivity (A) At a particular temperature (B) For circular bodies (C) Under thermal equilibrium (D) None of these

Last Answer : (C) Under thermal equilibrium

Thickness of stock does not affect the fuel economy of furnaces, if thematerial to be heated is of(A) Low emissivity(B) High thermal conductivity(C) Both (A) and (B)(D) Neither (A) nor (B)

Description : Thickness of stock does not affect the fuel economy of furnaces, if thematerial to be heated is of (A) Low emissivity (B) High thermal conductivity (C) Both (A) and (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) and (B)

What refers to the rate of thermal radiation emitter per unit area of a body?  A. Thermal conductivity  B. Absorptivity  C. Emissivity  D. Emissive power

Description : What refers to the rate of thermal radiation emitter per unit area of a body?  A. Thermal conductivity  B. Absorptivity  C. Emissivity  D. Emissive power

Last Answer : Emissive power

In turbulent flow, a rough pipe has the same friction factor as a smooth pipe (A) In the zone of complete turbulence (B) When the roughness projections are much smaller than the thickness of the laminar film (C) Everywhere in the transition zone (D) When the friction factor is independent of the Reynold's number

Description : In turbulent flow, a rough pipe has the same friction factor as a smooth pipe (A) In the zone of complete turbulence (B) When the roughness projections are much smaller than the thickness of ... ) Everywhere in the transition zone (D) When the friction factor is independent of the Reynold's number

Last Answer : (B) When the roughness projections are much smaller than the thickness of the laminar film

In the complete turbulence zone (in rough pipes), the (A) Rough and smooth pipes have the same friction factor (B) Laminar film covers the roughness projections (C) Friction factor depends upon NRe only (D) Friction factor is independent of the relative roughness

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Last Answer : (D) Friction factor is independent of the relative roughness

Film condensation is promoted on a/an __________ surface. (A) Oily (B) Coated (C) Clean & smooth (D) Dirty

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Last Answer : (C) Clean & smooth

The most conducive surface for dropwise condensation to occur is the __________ surface. (A) Coated (B) Oily (C) Glazed & polished (D) Smooth

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Last Answer : (B) Oily

Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be (A) 0.35 (B) 0.45 (C) 0.55 (D) 0.85

Description : Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be (A) 0.35 (B) 0.45 (C) 0.55 (D) 0.85

Last Answer : (B) 0.45

Pick out the wrong statement. (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment (B) The emissivity of a surface increases with increase in surface roughness (C) The emissivity of a polished surface is quite low (D) The emissivity of a non-metallic surface decreases with increase in the temperature

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Last Answer : (A) The emissivity of a surface decreases, if it gets corroded by atmospheric environment

The heating capacity of continuous reheating furnace depends upon the (A) Hearth area and furnace temperature (B) Emissivity of the stock (C) Ratio of wall surface to stock surface (D) All (A), (B) and (C)

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

For an ideal black body (A) Absorptivity = 1 (B) Reflectivity = 1 (C) Emissivity = 0 (D) Transmissivity = 1

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While the total emissivity of a perfect black body is unity, the same for a real body is(A) 0(B) 1(C) > 1(D) Between 0 and 1

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What is the emissivity of a black body? (A) 0 (B) 1 (C) 0.5 (D) 0.90

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In a certain plant rough seeds R are dominant and smooth seeds r RECESSIVE two plants with genotype?

Description : In a certain plant rough seeds R are dominant and smooth seeds r RECESSIVE two plants with genotype?

Last Answer : Need answer

Is limestone rough or smooth?

Description : Is limestone rough or smooth?

Last Answer : Limestone can be smooth but it is mostly rough. You can tell this just buy looking at some or feeling it.

If therapy with multiple drugs causes induction of drug metabolism in your asthma patient, it will (a) Result in increased smooth endoplasmic reticulum (b) Result in increased rough endoplasmic reticulum (c) Result in decreased enzymes in the soluble cytoplasmic fraction (d) Require 3-4 months to reach completion (e) Be irreversible

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Last Answer : Ans: A

What is the difference between smooth and rough endoplasmic reticulum ?

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The pollen grains of flowers pollinated by insects are : (1) smooth and dry (2) rough and sticky (3) rough and dry (4) large and, showy

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Last Answer : (2) rough and sticky Explanation: Pollen grains are large sticky and heavy, usually with rough surfaces so that they can readily cling onto the insects bodies. They are sticky so that pollen grains settling on them are not easily displaced.

Appearance of welded structures with respect to riveted structures is a. Smooth b. Rough c. Same d. None

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Epitheliogenesis imperfecta ligua bovis is a defect in which tongue is A A. Abnormally smooth B. Normally smooth C. Abnormally rough D. All of these

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Identify the components labelled A, B, C and D in the diagram below from the list (i) to (viii) given along withComponents : (i) Cristae of mitochondria (ii) Inner membrane of mitochondria (iii) Cytoplasm (iv) Smooth endoplasmic reticulum (v) Rough endoplasmic reticulum (vi) Mitochondrial matrix (vii) Cell vacuole (viii) Nucleus The correct components are: A B C D (a) (v) (iv) (viii) (iii) (b) (i) (iv) (viii) (vi) (c) (vi) (v) (iv) (vii) (d) (v) (i) (iii) (ii)

Description : Identify the components labelled A, B, C and D in the diagram below from the list (i) to (viii) given along with Components : (i) Cristae of mitochondria (ii) Inner membrane of mitochondria (iii) Cytoplasm (iv) Smooth endoplasmic ... viii) (vi) (c) (vi) (v) (iv) (vii) (d) (v) (i) (iii) (ii)

Last Answer : (a) (v) (iv) (viii) (iii)

Select the correct matching in the following pairs. (a) Rough ER – Synthesis of glycogen (b) Rough ER – Oxidation of fatty acids (c) Smooth ER – Oxidation of phospholipids (d) Smooth ER – Synthesis of lipids

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Nuclear envelope is a derivative of (a) microtubules (b) rough endoplasmic reticulum (c) smooth endoplasmic reticulum (d) membrane of Golgi complex.

Description : Nuclear envelope is a derivative of (a) microtubules (b) rough endoplasmic reticulum (c) smooth endoplasmic reticulum (d) membrane of Golgi complex.

Last Answer : (b) rough endoplasmic reticulum

A heavy ladder resting on floor and against a vertical wall may not be in equilibrium, if (A) The floor is smooth, the wall is rough (B) The floor is rough, the wall is smooth (C) The floor and wall both are smooth surfaces (D) The floor and wall both are rough surfaces

Description : A heavy ladder resting on floor and against a vertical wall may not be in equilibrium, if (A) The floor is smooth, the wall is rough (B) The floor is rough, the wall is smooth (C) The floor and wall both are smooth surfaces (D) The floor and wall both are rough surfaces

Last Answer : (C) The floor and wall both are smooth surfaces

Rankine's theory of earth pressure assumes that the back of the wall is (A) Plane and smooth (B) Plane and rough (C) Vertical and smooth (D) Vertical and rough

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Last Answer : Answer: Option C

The difference between smooth and rough endoplasmi reticulum is the lack of: a) ATP b) proteins c) ribosomes d) peroxisomes

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The pollen grains of flowers pollinated by insects are : (1) smooth and dry (2) rough and sticky (3) rough and dry (4) large and showy

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Last Answer : rough and sticky

Which is NOT a characteristic of emissivity?  A. It is high with most nonmetals  B. It is directly proportional to temperature  C. It is independent with the surface condition of the material  D. It is low with highly polished metals

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Last Answer : It is independent with the surface condition of the material

Recall homework 2 in which we calculated emissivity for a single layer atmosphere. If the atmosphere were to suddenly become a perfect emitter (i.e., if e = 1 rather than e = 0.8), what would happen to the surface temperature? (a) The surface temperature would be lower. (b) The surface temperature would be the same. (c) The surface temperature would be higher. (d) There would be initial warming followed by cooling as the planet moves toward radiative equilibrium.

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Last Answer : (c) The surface temperature would be higher.

What is the emissivity of a black body?  A. 0  B. 1  C. 0.5  D. 0.25

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Hot coffee is poured simultaneously in four metallic tumblers painted outside with different types of paints. After some time, the coffee will be found coldest in the tumbler painted (a) rough white (b) shining white (c) rough black (d) shining black

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