A current of 10A exists in a wire of cross-sectional area of 5 mm2 with a drift velocity of 2 × 10 - 3 ms ⁻¹. The number of free electrons in each cubic meter of the wire is ___________. (a) 625 × 1025 (b) 1 × 1023 (c) 2 × 1025 (d) 2 × 106

Answer: (a). I = neAvd ⇒ n = (I)/(eAvd) n = 101.6 × 10⁻¹⁹ × 5 × 10⁻⁶ × 2 × 10⁻³ = 101.6 × 10⁻²⁷ n = 6.25 × 10²⁷ = 625 × 10²⁵ m⁻³ So the answer is (a).

A current of 10A exists in a wire of cross-sectional area of 5 mm2… | JEE Main 2021 (17 Mar, Shift 1)

Q20JEE Main 2021 · 17 MAR · SHIFT 1Easy

Electric Current, Drift Velocity & Current Density

A current of 10A exists in a wire of cross-sectional area of 5 mm2 with a drift velocity of 2 $\times$ 10 $-$ 3 ms ${}^{-1}$ . The number of free electrons in each cubic meter of the wire is ___________.

Show answer and solution

Answer: (a)

$I = neAv_d \Rightarrow n = \dfrac{I}{eAv_d}$
$n = \dfrac{10}{1.6 \times 10^{-19} \times 5 \times 10^{-6} \times 2 \times 10^{-3}} = \dfrac{10}{1.6 \times 10^{-27}}$
$n = 6.25 \times 10^{27} = 625 \times 10^{25}\text{ m}^{-3}$
So the answer is (a).

Report a mistake

Electric Current, Drift Velocity & Current Density question from JEE Main 2021 (17 Mar, Shift 1)

More questions on Electric Current, Drift Velocity & Current Density