Question

A uniform copper wire having a cross sectional area of 1 mm² carries a current of 5 A. Calculate the drift speed of free electrons in it. 

(Free electron number density of copper = 2 × 10²⁸/m³.)

Answer 1

Given: n = 2 × 10²⁸/m³

A = 1 mm² = 10⁻⁶ m²

I = 5 A

e = 1.6 × 10⁻¹⁹ C

v_d = ?

I = neAv_d

v_d = `I/(n eA)`

= `5/(2 xx 10^28 xx 1.6 xx 10^-19 xx 10^-6)`

= 1.5625 × 10⁻³ m/s

= 1.56 mm/s