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4

Magnetic permeability of iron is increased by its

A. Decarburising

B. Alloying with cobalt

C. Purification

D. Alternate heating & cooling

Correct Answer :

B. Alloying with cobalt


Related Questions

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4

Aluminium is extracted from

A. Chalcocite

B. Bauxite

C. Galena

D. None of these

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4

__________ temperature remains constant during adiabatic saturation process of unsaturated air.

A. Dew point

B. Dry bulb

C. Wet bulb

D. None of these

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4

Between 230 and 370°C, blue brittleness is caused in mild steel because of the

A. Immobility of dislocation

B. Strain-ageing

C. Increase in Young's modulus

D. Strain hardening

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4

In the blast furnace, incorporation of water vapour in the blast gives the following effect.

A. Increases the reducing potential of the gas

B. Increases the flame temperature

C. No significant change occurs

D. Increases the hydrogen content in the metal

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4

The cathode in an electrochemical cell always carries

A. Negative charge

B. Positive charge

C. Zero charge

D. Positive or negative charge depending upon the nature of the cell

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4

Out of the following substances, one ton of __________ will store the maximum heat for a rise of 30°C in temperature.

A. Steel

B. Lignite

C. Water

D. Lime stone

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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

Strain hardening effect in a metal subjected to cold working is due to the __________ mechanism.

A. Fracture

B. Dislocation

C. Slip

D. Twinning

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4

Heat transfer to the water wall in a high pressure water wall type boiler furnace is mainly by

A. Conduction

B. Convection

C. Radiation

D. Both 'a' & 'b'

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4

Magnetic permeability of iron is increased by its

A. Decarburising

B. Alloying with cobalt

C. Purification

D. Alternate heating & cooling

What is the correct answer?

4

__________ cannot increase the fatigue strength of a material.

A. Grain refining

B. Grain coarsening

C. Surface hardening

D. Shot peening

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4

Increasing the carbon content of steel

A. Reduces the upper shelf energy

B. Increasing the ductility transition temperature

C. Decreases brittleness

D. Decreases hardness

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4

The heat treatment to which the steel wire containing > 0.25% carbon is subjected to is

A. Full annealing

B. Bright annealing

C. Patenting

D. None of these

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4

Titanium is produced by __________ of Ti Cl4.

A. Electrolytic reduction

B. Calcium reduction

C. Magnesium reduction

D. Thermal dissociation

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4

A 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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4

What is the value of entropy at 273°K?

A. 0

B. 1

C.

D. None of these

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4

Friction factor for fluid flow in pipe does not depend upon the

A. Pipe length

B. Pipe roughness

C. Fluid density & viscosity

D. Mass flow rate of fluid

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4

The dew point temperature lines on psychrometric charts are straight inclined sloping downwards to the right. When relative humidity of moist air is 100%, then

A. Wet bulb temperature=dry bulb temperature

B. Wet bulb temperature=dew point temperature

C. Saturation temperature=dew point temperature

D. All 'a', 'b' & 'c'

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4

Sub zero treatment of steel is done to

A. Suppress martensite transformation

B. Enhance its working performance in sub zero atmosphere

C. Reduce the retained austenite in hardened steel

D. Induce temper brittleness after its hardening

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4

A compact estimate about the amount of materials handling between various work stations is obtained from the

A. Gantt chart

B. Bin chart

C. String diagram

D. Travel chart

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4

Pick out the wrong statement about nucleate boiling.

A. Bubble generation is by expansion of entrapped gas/vapour at small cavities in the surface

B. Surface temperature is greater than the saturation temperature of the liquid

C. Heat transfer from the surface of the liquid is less than that in film boiling

D. The temperature is less than that of film boiling

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4

Diffusion co-efficient of a metal in a solid solution depends upon its

A. Composition

B. Temperature

C. Both (A) & (B)

D. Neither (A) nor (B)

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4

Oxygen cylinders used for autogenous (cutting/welding) purposes are

A. Seamless & made of steel

B. Heat treated before use

C. Made by sand casting

D. Welded steel cylinders

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4

Hollow shafts can be made as strong as solid shafts by making the twisting moments of both the shafts same. Shafts made by __________ have residual stresses.

A. Forging

B. Cold rolling

C. Hot rolling

D. Casting

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4

Consider an ideal solution of components A and B. The entropy of mixing per mole of an alloy containing 50% B is

A. R ln 2

B. -R ln 2

C. 3 R ln 2

D. -3R ln 2

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4

In __________ process, there is an increase in entropy with no degradation of energy.

A. Isothermal expansion

B. Isochoric heat addition

C. Polytropic expansion

D. Isobaric heat addition

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4

Annealing of cast iron

A. Softens it to facilitate machining

B. Decreases the free carbon

C. Increases the strength

D. None of these

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4

A fluid is termed as the Newtonian fluid, when the shear stress is __________ the velocity gradient.

A. Independent of

B. Inversely proportional to

C. Directly proportional to

D. None of these

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4

Two wires of the same radius & material having length in the ratio of 1 : 2 are stretched by the same force. The strain produced in the two wires will be in the ratio of

A. 1 : 1

B. 1 : 2

C. 2 : 1

D. 1 : 4

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4

Consideration of the creep is the most important in case of the

A. Blades of gas turbine

B. Piston of an I. C. engine

C. Flywheel of steam engine

D. Cycle chain