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When the temperature of a metallic conductor rises, its resistivity increases mainly because:
Athe free-electron number density decreases
Bthe wire becomes longer
Cthe average collision time of electrons decreases
Dthe charge of each electron increases
Answer & Solution
Correct answer: C. the average collision time of electrons decreases
From ρ = m/(ne²τ): in a metal n is essentially constant, but rising temperature increases collision frequency, reducing τ, so ρ increases.
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