If an insulating material is operated beyond the maximum allowable temperature, its life is

A steam carraying pipeline is insulated with two layers of insulating materials with the inferior insulation material forming the inner part. If the two insulating layers are interchanged, the heat conducted will

A

Increase

B

Decrease

C

Remain unaffected

D

May increase or decrease; depends on the thickness of each layer

An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture?

A

Cork

B

Saw dust

C

Sand

D

Chemically prepared foam

Out of the following themocouple wire insulating material, the highest temperature rating is for

A

Teflon

B

Ceramic fibre

C

Asbestos

D

Fibre glass

The insulating material for a cable should have

A

Low cost

B

High dielectric strength

C

High mechanical strength

D

All of the above

The insulating material for cables should

A

Be acid proof

B

Be non-inflammable

C

Be non-hygroscopic

D

Have all above properties

Surface resistance of an insulating material is reduced due to the

A

Smoky and dirty atmosphere

B

Humidity in the atmosphere

C

Both A and B

D

Neither A nor B

The insulating material used between the commutator segments is normally

A

Graphite

B

Paper

C

Mica

D

Insulating varnish

Out of the following which is an insulating material?

A

Copper

B

Gold

C

Silver

D

Paper

The insulating material should have

A

Low permittivity

B

High resistivity

C

High dielectric strength

D

All of the above

The disadvantage with paper as insulating material is

A

It is hygroscopic

B

It has high capacitance

C

It is an organic material

D

None of the above

If an insulating material is operated beyond the maximum allowable temperature, its life is

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