Drift velocity is constant in a uniform conductor

Steps:

• Drift velocity $v_d = \frac{e E \tau}{m}$, where $E$ is the electric field.
• In a uniform conductor with steady current, $E$ is constant along the length.
• Thus, $v_d$ remains constant with distance $x$.
• Graph A shows constant $v$ vs. $x$.

Why A is correct:

• Matches Ohm's law and uniform field, yielding constant drift speed.

Why the others are wrong:

• B: Shows increasing $v$, implying non-uniform accelerating field, not steady state.
• C: Shows decreasing $v$, suggesting field weakening, incorrect for uniform conductor.
• D: Likely zero or varying nonlinearly, ignoring constant current flow.

Final answer: A