Drift speed of electrons in a copper wire of cross-section A carrying current I is approximately:

1. Typical free-electron number density in Cu ≈ 8.5 × 10²⁸ m⁻³. 2. For I = 1 A in a 1 mm² wire, v_d = I/(n e A) ≈ 7 × 10⁻⁵ m s⁻¹ ≈ a few mm s⁻¹ at best, often much less. 3. Even though drift speed is tiny, electric signals (waves) travel at near light-speed through the wire. _Source: syllabus Physics Ch 3 §3.4 (drift-speed estimates)_