71. Stainless steels are alloys of:

1. 1. Fe and Ni

   
   
   

   2. Fe, Cr and Ni

   
   
   

   3. Fe, Cr and Mo

   
   
   

   4. None of these

   
   
   

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   Stainless steels are alloys of Fe, Cr and Ni.

   Correct Option: B

   Stainless steels are alloys of Fe, Cr and Ni.

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72. Ionic bonding in solids depends primarily on:

1. 1. Vander Waals forces

   
   
   

   2. electrical dipoles

   
   
   

   3. sharing of electrons

   
   
   

   4. transfer of electrons

   
   
   

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   Ionic bonding in solids depends primarily on transfer of electrons.

   Correct Option: D

   Ionic bonding in solids depends primarily on transfer of electrons.

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73. In photoelectron emission, the threshold frequency is defined as the:

1. 1. minimum frequency at which field emission begins

   
   
   

   2. lowest frequency at which photoemission of electron starts

   
   
   

   3. maximum frequency at which photoemission of electron stops

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   In photoelectron emission, the threshold frequency is defined as the minimum frequency at which field emission begins.

   Correct Option: A

   In photoelectron emission, the threshold frequency is defined as the minimum frequency at which field emission begins.

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74. Schottky effect describes:

1. 1. effect of intensive electric field on the rate of electron emission from a cathode

   
   
   

   2. current in temperature limited region

   
   
   

   3. current in space charge region

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Schottky effect describes the effect of intensive electric field on the rate of electron emission from a cathode.

   Correct Option: A

   Schottky effect describes the effect of intensive electric field on the rate of electron emission from a cathode.

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75. Which one of the theories given below is related to the theory of the thermocouple?

1. 1. Piezoelectric effect

   
   
   

   2. Skin effect

   
   
   

   3. Seebeck effect

   
   
   

   4. Faraday’s Law

   
   
   

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   NA

   Correct Option: C

   NA

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