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Percentage of free space in cubic close packed struchure and in body centred structure are respectively.A. 48% and 26%B. 30% and 26%C. 26% and 32%D. 32% and 48%

Answer» Correct Answer - C
For FCC or CCP
`4r=sqrt(2)a`
`P . F =(nxx(4)/(3)pir^(3))/(a^(3))`
`n=4,a=2sqrt(2r)`
P.F. = 74%
Free space = 100 - 74 = 26%
For BCC
`4r=sqrt(3)a`
P.E. `=(2xx(4)/(3)pir^(3))/((4)/(sqrt(3))r)^(3)`
P.F. = 68%
Free space = 32%


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