If the ratio of the concentration of electron to that of holes in a semiconductor is `(7)/(5)` and the ratio of current is `(7)/(4)` then what is the ratio of their drift velocities ?

Options

A. `5/4`
B. `4/7`
C. `5/8`
D. `4/5`

Answer

A

Explanation

Given : `n_e/n_h=7/5` and `I_e/I_h=7/4`
Drift velocity `v_d=I/(n_eA) therefore v_d prop I/n`
`therefore v_e/v_h=(I_e/I_h) xx(n_h/n_e) = 7/4xx5/7=5/4`