81. The number of effective atoms per unit cell in a FCC structure is:

1. 1. one

   
   
   

   2. four

   
   
   

   3. six

   
   
   

   4. two

   
   
   

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   NA

   Correct Option: B

   NA

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82. A material is most stable when its potential energy is:

1. 1. maximum

   
   
   

   2. infinite

   
   
   

   3. minimum

   
   
   

   4. zero

   
   
   

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   A material is most stable when its potential energy is minimum.

   Correct Option: C

   A material is most stable when its potential energy is minimum.

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83. In the above question, the potential energy at infinity will be equal to:

1. 1. ∞

   
   
   

   2. - A

      r2

   
   
   

   3. zero

   
   
   

   4. a constant finite value

   
   
   

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   NA

   Correct Option: C

   NA

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84. Bond energy of a solid is defined at:

1. 1. r > r₀

   
   
   

   2. r = r₀

   
   
   

   3. r < r₀

   
   
   

   4. r → ∞

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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85. A primitive cell is:

1. 1. the cell containing smallest group of atoms randomly

   
   
   

   2. an unit cell in which lattice points are located only at its corners

   
   
   

   3. a basic building block of a crystal

   
   
   

   4. an unit cell of end centred monoclinic crystal

   
   
   

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1. View Hint View Answer Discuss in Forum

   Primitive cell is an unit cell in which lattice points are located only at its corners.

   Correct Option: B

   Primitive cell is an unit cell in which lattice points are located only at its corners.

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