J & K CET Engineering J and K - CET Engineering Solved Paper-2014

  • question_answer
    What is the percentage of free space in body centered cubic unit cell?

    A)  32%            

    B)  20%

    C)  34%            

    D)  28%

    Correct Answer: A

    Solution :

     For bcc unit cell, \[\text{Packing}\,\text{fraction}\,\text{=}\frac{\text{Total}\,\text{volume}\,\text{of}\,\text{spheres}}{\text{Volume}\,\text{of}\,\text{the}\,\text{unit}\,\text{cell}}\] \[\text{=}\frac{\frac{8}{3}\pi {{r}^{3}}}{\frac{64}{3\sqrt{3}}{{r}^{3}}}=0.68\]. \[\therefore \]% of occupied space \[=0.68\times 100\] \[=68%\] \[\therefore \]% of free space\[~=100-68=32%\]


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