Question

In a pure semiconductor , the number of conduction electron is $6\times {10}^{19}$ per cubic metre. How many holes are there in a sample of size $1cm\times 1cm\times 2mm$?

Answer 1

The number of conduction electron is $6\times {10}^{19}/m^3$
$Volume=1cm\times 1cm\times 2mm$
$={10}^{-2}m\times {10}^{-2}\times 2\times {10}^{-3}M$
$={10}^{-2\times {10}^{-2}\times 2\times {10}^{-3}{m}^3}$
Volume $=2{\times }^{-7}{m}^3$
$1m^3$ has $6\times {10}^{19}$ no of electron
$2\times {10}^{-7}{m}^3$ has $x$ no of electron
$x=2\times 6\times {10}^{-7}\times {10}^{19}$
$=12\times {10}^{12}$ no of $e^{-}$