The drift velocity v_d of conduction electrons is related to current density J (n = number density, e = electron charge) by:

1. Number of charges crossing unit area per second = n v_d. 2. Each contributes a charge e, so current density J = n e v_d. 3. Typical drift speed in copper wire is ~10⁻⁴ m s⁻¹ — surprisingly slow. _Source: syllabus Physics Ch 3 §3.4 Drift Velocity and Current_