Sample 1Medium
A copper wire of cross-sectional area 1.0 × 10⁻⁶ m² carries a current of 1.36 A. The number density of free electrons in copper is 8.5 × 10²⁸ m⁻³ and e = 1.6 × 10⁻¹⁹ C. The drift speed of the electrons is
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The answer is C.
v_d = I/(neA) = 1.36/(8.5 × 10²⁸ × 1.6 × 10⁻¹⁹ × 10⁻⁶) = 1.36/(1.36 × 10⁴) = 1 × 10⁻⁴ m s⁻¹.
- A.
1 × 10⁻² m s⁻¹ is a hundred times larger than I/(neA).
- B.
1 × 10⁻⁶ m s⁻¹ is a hundred times smaller than I/(neA).
- D.
1 × 10⁻³ m s⁻¹ is ten times larger than I/(neA).
NCERT: Class 12 Physics, Chapter 3, Drift of electrons and the origin of resistivity