If potential difference V applied across a metallic wire is increased by V, how will the drift velocity of the electrons change?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → becomes twice
The drift velocity of electrons is proportional to the electric field in the wire, and the field is the potential difference per unit length.
\( \displaystyle v_d = \frac{eE\tau}{m} = \frac{eV\tau}{m\,l} \)
Here \( \tau \) (relaxation time), \( m \), \( e \) and the length \( l \) do not change, so \( v_d \propto V \).
Increasing \( V \) by \( V \) makes the potential difference \( V + V = 2V \), so the drift velocity becomes twice.