Question

Which expression gives the drift velocity in terms of electric field \[E\], relaxation time \[\tau\], electronic charge \[e\], and electron mass \[m\]?

Options

• \[v_d=-\frac{eE}{m\tau}\]

• \[v_d=\frac{I}{A}\]

• \[v_d=-\frac{eE\tau}{m}\]

• \[v_d=\frac{ne^2\tau}{m}\]

Answer 1

The drift velocity is \[v_d=-\frac{eE\tau}{m}\]. The negative sign indicates that electron drift is opposite to the electric field.