Question

In pure semiconductor, the number of conduction electrons is $6 \times 10^{18}$ per cubic metre. How many holes are there in a sample of size $1\, cm \times 1\, cm \times 1\, mm$?

• A. $3 \times 10^{10}$
• B. $6 \times 10^{11}$
• C. $3 \times 10^{11}$
• D. $6 \times 10^{10}$

Answer 1

Answer: (B)

Here, $n_e = 6 \times 10^{18}\, m^{-3}$
Volume of the sample $= 1 \,cm \times 1 \,cm \times 1\, mm $
$= 10^{-7}\, m^{3}$
Number of holes in the sample = Number of electrons in the sample
$= n_e \times V $
$= 6 \times 10^{18} \times 10^{-7}$
$ = 6 \times 10^{11}$