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In a conductor, if the number of conduction electrons per unit volume is 8.5 × 10 28 m –3 and mean free time is 25 f s (femto second), it's approximate resistivity is : (m e = 9.1 × 10 –31 kg)

1. 10 –5 Ω m
2. 10 –7 Ω m
3. 10 –8 Ω m
4. 10 –6 Ω m

Correct answer: 10 –8 Ω m

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