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4

With increase in temperature, the electrical conductivity of semiconductors

A. Increases

B. Decreases

C. Remain constant

D. Either (A) or (B), depends on the type of semi-conductor

Correct Answer :

A. Increases


Related Questions

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4

Diamagnetic materials

A. Are magnetised by eddy currents only

B. Are non-magnetic and cannot be magnetised

C. Are magnetised in direction opposite to the magnetic field

D. Can be magnetised in one direction only

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4

At the point of boundary layer separation in fluid flow, the

A. Shear stress is maximum

B. Velocity gradient is flat

C. Density variation is maximum

D. Shear stress is zero

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4

Out of the following, the lowest packing of atoms exists in __________ crystal lattice structure.

A. Hexagonal close, packed (hcp)

B. Face centred cubic (fcc)

C. Body centred cubic (bcc)

D. Simple cubic

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4

A material is capable of resisting softening at high temperature, because of its property termed as

A. Hot temper

B. Hot hardness

C. Fatigue

D. Creep

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4

As per international norms, the maximum permissible value of noise level in the industrial environment is __________ decibels as measured at a distance of 1.5 metres from the source of noise.

A. 110

B. 85

C. 60

D. 45

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4

The surface tension of a liquid, at critical temperature is

A. Indeterminate

B. Zero

C. Infinity

D. Same as that at any other temperature

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4

The malleability of a material is the property by virtue of which it can be rolled or hammered into thin sheets. Which of the following materials has the maximum malleability?

A. Lead

B. Copper

C. Aluminium

D. Wrought iron

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4

Corrosion is

A. A physical phenomenon

B. A chemical phenomenon

C. Same as erosion

D. An uncontrollable phenomenon

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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

A material subjected __________ must have high resilience.

A. Shock loading

B. Vibration

C. Fatigue

D. Tension

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4

Fibrous fracture is normally encountered in the __________ materials.

A. Hard

B. Elastic

C. Ductile

D. Brittle

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4

Pick out the wrong statement.

A. Molecules with symmetrical arrangements (e.g. CH4 or CCl4) are non-polar

B. Generally, non-polar compounds are chemically inactive, conduct electricity poorly and do not ionise

C. Most of the hydrocarbons are non-polar

D. None of these

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4

Specific gravity of a metal, which weighs 5 kg in air and 4 kg when submerged in water, will be

A. 5

B. 1.25

C. 2.5

D. 3.75

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4

Stellite is a __________ material.

A. Ferrous

B. Ceramic

C. Cemented carbide

D. Non-ferrous cast alloy cutting tool

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4

Joining of thin foils is preferred to be done by

A. Gamma rays

B. X-rays

C. Microwaves

D. Gas welding

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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

Percentage of argon (by volume) in dry atmospheric air is about

A. 0.09

B. 0.3

C. 0.57

D. 0.94

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4

Which of the following represents the correct time-temperature curve when a block of metal is heated above room temperature & then left to cool in the room following Newton's law of cooling in which the rate of temperature drop will go on decreasing with the passage of time.

A.

B.

C.

D.

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4

In inventory control theory, the economic order quantity (EOQ) is the

A. Lot size corresponding to break even analysis

B. Average level of inventory

C. Optimum lot size

D. None of these

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4

A form of stress corrosion failure termed as 'season cracking' is generally observed in

A. Thermosetting polymers

B. High carbon steels

C. Brasses

D. Borosilicate glasses

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4

What is the pH of distilled water?

A. 0

B. 1

C. 7

D. 14

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4

What is the range of tempering temperature (°C) for most of the materials?

A. 75-100

B. 200-300

C. 350-450

D. 500-600

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4

The function of neutral flux used in the pyrometallurgy of metal extraction is to increase the __________ of the slag.

A. Fluidity

B. Basicity

C. Acidity

D. Viscosity

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4

Parallel straight line pattern of temperature distribution for both hot and cold fluids is observed in case of heat exchanger of the type

A. Parallel flow with equal heat capacities

B. Counter flow with equal heat capacities

C. Counter flow with unequal heat capacities

D. Parallel flow with unequal heat capacities

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4

Damage to metal surface by mechanical action is called

A. Pitting

B. Corrosion

C. Erosion

D. None of these

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4

The ability of tool steel to resist softening at high temperatures is termed as __________ hardness.

A. Red

B. Extended

C. Super

D. Extreme

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4

Surface tension of a liquid

A. Is due to intermolecular forces of cohesion

B. Decreases with rise in temperature

C. Is responsible for the spherical shape of an isolated liquid drop

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

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4

As the fluid flow rate increases, the float of the Rotameter

A. Rises in the tube

B. Rotates at higher speed

C. Rotates at lower speed

D. Drops down in the tube

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4

Silicon percentage in silicon steel used for electrical equipments is about

A. 1

B. 4.0

C. 8

D. 14

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4

The condition of diffraction from a crystal is given by

A. nλ = 2d Sin θ

B. λ = d Sin 2θ

C. λ = 2d Sin 2θ

D. nλ = d Sin θ