Q128 / 150 · JEE Main 2006 · Physics
If the ratio of the concentration of electrons that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$, then what is the ratio of their drift velocities?
- A$\frac{4}{7}$
- B$\frac{5}{8}$
- C$\frac{4}{5}$
- Correct answerD$\frac{5}{4}$
Solution
$\frac{\mathrm{n}_{\mathrm{e}}}{\mathrm{n}_{\mathrm{n}}}=\frac{7}{5} \frac{\mathrm{l}_{\mathrm{e}}}{\mathrm{l}_{\mathrm{n}}}=\frac{7}{4}$
$\frac{\left(\mathrm{V}_{\mathrm{d}}\right)_{\mathrm{e}}}{\left(\mathrm{V}_{\mathrm{d}}\right)_{\mathrm{n}}} \Rightarrow \frac{\mathrm{l}_{\mathrm{e}}}{\mathrm{l}_{\mathrm{n}}} \times \frac{\mathrm{n}_{\mathrm{n}}}{\mathrm{n}_{\mathrm{e}}}=\frac{5}{4}$
Hence, the correct answer is option: 'D'.