Question

If the ratio of the concentration of electrons to that of holes in a semiconductors is $\frac{7}{5}$ and the ratio of currents is$\frac{7}{4}$, then the ratio of drift velocities is

• A. $\frac{5}{8}$
• B. $\frac{4}{5}$
• C. $\frac{5}{4}$
• D. $\frac{4}{7}$

Answer 1

Answer: (C)

The drift velocity of charge carriers in the material of constant cross-sectional area A is given as:
$v=\frac{I}{nAq}$(here I is the current flowing through the material, n is the charge-carrier density, and q is the charge on the charge-carrier.)
We have the ratio of I as $\frac{7}{4}$ and ratio of n as $\frac{7}{5}$.
Thus we get the ratio of v as $\frac{5}{4}$