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Question:

Drift speed of electrons, when 1.5A of current flows in a copper wire of cross section 5mm², 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)

3

0.2

2

0.02

Solution:

The correct option is D
0.02
I = neAvd ⇒ vd = I/neA = 1.5/(9 × 10²⁸ × 1.6 × 10⁻¹⁹ × 5 × 10⁻⁶) = 0.02mm/s