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4

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

Correct Answer :

A. 2


Related Questions

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4

Air/fuel ratio on molar (volume) basis for combustion of methane with theoretical quantity of air with be

A. 9.5 : 1

B. 12.5 : 1

C. 15.5 : 1

D. 18.5 : 1

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4

Referring to the periodic table of elements, it is found that with increasing atomic number. The atomic size in the same

A. Period increases

B. Period decreases

C. Group increases

D. Both 'b' & 'c'

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4

Flue gases pass through the following boiler accessories in a high pressure natural circulation boiler.
A. Induced draft fan
B. Economiser
C. Air preheater
D. Steam superheater Which of the following gives the correct sequence of flow of the flue gases through the above mentioned boiler accessories?

A. A, C, B, D

B. D, B, C, A

C. D, C, B, A

D. D, A, B, C

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4

Mild steel has __________ crystal lattice structure.

A. Face centred cubic (fcc)

B. Body centred cubic (bcc)

C. Orthorhombic

D. Cubic

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4

__________ are normally subjected to sub-zero treatment.

A. Highly stressed parts

B. Gauges or precision parts

C. Cold rolled sheets

D. Non machinable materials

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4

In troposphere (the weather domain), the temperature 't' at height 'h' above the sea level in metres is given by (where, temperature at sea level is 15°C and t is in °C.)

A. t = 15 - 0.0065 h

B. t = 15 + 0.0065 h

C. t = 0.0035 h - 15

D. t = 15 - 0.0035 h

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4

If the head is doubled in & centrifugal pump, the power required will increase in the ratio of

A. 23

B. 23/2

C. 25/2

D. 21/3

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4

In an amorphous material, atoms defy any definite atomic structure and exist in random pattern just like in liquid. Which of the following is an amorphous material?

A. Tin

B. Lead

C. Zinc

D. Glass

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4

The fugacity of liquid water at 298 K is approximately 3171 Pa. Considering the ideal heat of vaporisation as 43723 J/gm.mole, its fugacity at 300 K would be

A. 3171Pa

B. 3567Pa

C. 1.01 × 105Pa

D. 5000Pa

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4

Which of the following is normally not found in both the S.I. (petrol) & C.I. (diesel) engines?

A. Air filter

B. Fuel injector

C. Exhaust silencer

D. Battery

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4

Ammonia leakage in the refrigeration system is detected by

A. Sulphur stick, which on detection gives white smoke

B. Using chemical reagents

C. Its smell

D. Soap solution

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4

Wrought iron does not have

A. Uniform strength in all directions

B. Ability to hold protective coating

C. High ductility & corrosion resistance

D. Easily weldable characteristics

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4

Which one of the following is incombustible?

A. H2

B. CCl4

C. C2H2

D. S

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4

The materials which fracture even at small strains are termed as brittle, while those materials which exhibit an appreciable deformation before failure are termed as

A. Rigid

B. Tough

C. Ductile

D. Plastic

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4

Pick out the wrong statement about the machinability of metals. Machinability of a metal

A. Decreases with increase in strain hardening tendencies

B. Decreases with increase in hardness, in general

C. Depend on the composition, microstructure and physical & mechanical properties

D. Decreases with increases in tensile strength & decrease in grain size

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4

Which of the following is not a charge material for cupola?

A. Limestone

B. Iron scrap

C. Iron ore

D. Pig iron

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4

Which of the following is preferred for riveting?

A. Lap joint

B. Butt joint

C. Either (A) or (B)

D. Neither (A) nor (B)

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4

Material of construction of the electrode used in the electric resistance welding is

A. Stainless steel

B. Graphite

C. Copper

D. Steel

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4

Addition of __________ to steel does not help in improving its machinability.

A. Sulphur

B. Silicon

C. Lead

D. Phosphorous

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4

Multistage compression of air as compared to single stage compression offers the advantage of

A. Power saving per unit weight of air delivered

B. Moisture elimination in the inter-stage cooler

C. Increased volumetric efficiency

D. All (A), (B) & (C)

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4

Galvanic corrosion cannot be prevented by

A. Cathodic protection

B. Anodic protection

C. Usage of largest possible anodic area

D. Any one of these

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4

Maximum amount of thermal radiation is emitted at all wavelengths at any specified temperature by a/an __________ body.

A. Grey

B. Black

C. Opaque

D. White

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4

Air/fuel ratio by weight for combustion of methane with theoretical quantity of air will be about

A. 9 : 1

B. 17 : 1

C. 23 : 1

D. 29 : 1

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4

Oxide layer formed on the non-ferrous metal surface after its annealing is

A. Removed by acid pickling

B. Hammered into the surface

C. Removed with coarse emery cloth

D. Left as such to protect the surface

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4

Electrostatic separation of minerals from each other is based on their differences in the following property.

A. Densities

B. Magnetic permeabilities

C. Electrical conductivities

D. Hardness

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4

Which of the following terminology is used for the temperature at which new grains are formed in a metal?

A. Eutectic temperature

B. Lower critical temperature

C. Recrystallisation temperature

D. Upper critical temperature

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4

Which of the following has the highest value of refractive index?

A. Brine (sea water)

B. Diamond

C. Distilled water

D. Glass

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4

Shampoos are commercially not available in the form of

A. Powder

B. Gaseous mixture

C. Solution

D. Emulsion

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4

Which of the following is an undesirable property of slag produced during the Pyrometallurgical method of metal extraction from its ore?

A. High fusibility & fluidity

B. High thermal conductivity

C. Low density

D. High chemical activity

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4

The substance used as a smoke screen in warfare is

A. C2H2

B. SiCl4

C. P2O5

D. PCl5