The drift velocity of electrons in a copper wire carrying steady curre…

Question

The drift velocity of electrons in a copper wire carrying steady current is of the order of

Accepted Answer

B. {'text': '10⁻⁴ m/s', 'label': 'B'}

1. From v_d = -eEτ/m, drift velocity is proportional to field and relaxation time.
2. With typical current densities and free-electron density n ~ 10²⁸ m⁻³, |v_d| = I / (n e A).
3. For a copper wire this evaluates to about 10⁻⁴ m/s.
4. So drift velocity is remarkably small compared to thermal (~10⁶ m/s) or signal speeds.
_Source: NCERT Class 12 Physics, Ch 3 "Current Electricity", §3.5_

Answer

{'text': '10⁻¹ m/s', 'label': 'A'}

Answer

{'text': '10³ m/s', 'label': 'C'}

Answer

{'text': '10⁸ m/s', 'label': 'D'}