Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section 5 mm2, is v. If the electron density in copper is 9 × 1028/m3 the value of v. in mm/s is close to (Take charge of electron to be = 1.6 × 10 - 19C) (a) 0.02 (b) 3 (c) 2 (d) 0.2

Answer: (a). v = I/neA v = 1.59 × 10²⁸ × 1.6 × 10⁻¹⁹ × 5 × 10⁻⁶ = 1.57.2 × 10⁴ v ≈ 2.1 × 10⁻⁵ m/s = 0.02 mm/s So the answer is (a) 0.02.

Drift speed of electrons, when 1.5 A of current flows in a copper… | JEE Main 2019 (9 Jan, Shift 1)

Q27JEE Main 2019 · 9 JAN · SHIFT 1Easy

Electric Current, Drift Velocity & Current Density

Drift speed of electrons, when 1.5 A of current flows in a copper wire of cross section 5 mm2, is $v$ . If the electron density in copper is 9 $\times$ 1028/m3 the value of $v$ . in mm/s is close to (Take charge of electron to be = 1.6 $\times$ 10 $-$ 19C)

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Answer: (a)

$v = \dfrac{I}{neA}$
$v = \dfrac{1.5}{9 \times 10^{28} \times 1.6 \times 10^{-19} \times 5 \times 10^{-6}} = \dfrac{1.5}{7.2 \times 10^{4}}$
$v \approx 2.1 \times 10^{-5}\text{ m/s} = 0.02\text{ mm/s}$
So the answer is (a) 0.02.

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