NCERT Exercise 3.9 - Current Electricity
Question: The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 × 10²⁸ m⁻³. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 × 10⁻⁶ m² and it is carrying a current of 3.0 A.
Answer: Time for electron to drift 3.0 m = **2.7 × 10⁴ s** (≈ 7.6 hours).
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