The number density of free electrons in copper is nearly 8×10²⁸ m⁻³. A copper wire has its area of cross section = 2×10⁻⁶ m² and is carrying a current of 3.2 A. The drift speed of the electrons is ______ m/s.
(a) 125 × 10⁻⁶
(b) 250 × 10⁻⁶
(c) 375 × 10⁻⁶
(d) 500 × 10⁻⁶
Answer & Solution:
Answer: (a) 125 × 10⁻⁶ m/s
Solution: Using the formula I = nAevₐ, we get vₐ = I/(nAe) = 3.2/(8×10²⁸ × 2×10⁻⁶ × 1.6×10⁻¹⁹) = 125 × 10⁻⁶ m/s.