241. All of the following ceramic materials are isotropic except:

1. 1. SiO₄

   
   
   

   2. SiO₂

   
   
   

   3. MgSiO₃

   
   
   

   4. Al₂O₃

   
   
   

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   NA

   Correct Option: C

   NA

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242. The fatigue failure of a material can be avoided by:

1. 1. coating the surface

   
   
   

   2. shot peening

   
   
   

   3. nitriding

   
   
   

   4. any of these

   
   
   

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   In general the fatigue life of a component can be improved by improving the surface conditions.

   Correct Option: A

   In general the fatigue life of a component can be improved by improving the surface conditions.

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243. A ductile feature is usually not preceded by:

1. 1. large amount of non-recoverable energy absorption

   
   
   

   2. plastic flow

   
   
   

   3. deformation

   
   
   

   4. noise

   
   
   

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   NA

   Correct Option: D

   NA

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244. For a magnetic material when temperature is raised above Curie temperature, the material will become:

1. 1. ferromagnetic

   
   
   

   2. paramagnetic

   
   
   

   3. diamagnetic

   
   
   

   4. semiconductor

   
   
   

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   For a magnetic material when temperature is raised above Curie temperature, the material will become paramagnetic.

   Correct Option: B

   For a magnetic material when temperature is raised above Curie temperature, the material will become paramagnetic.

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245. When the temperature of a semiconductor is reduced to absolute zero?

1. 1. All electrons become free

   
   
   

   2. Electrons wave of higher velocities

   
   
   

   3. All valence electrons remain in the valence bands

   
   
   

   4. All valence electrons shift to forbidden gap

   
   
   

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   When the temperature of a semiconductor is reduced to absolute zero all valence electrons remain in the valence bands.

   Correct Option: C

   When the temperature of a semiconductor is reduced to absolute zero all valence electrons remain in the valence bands.

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