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InterviewSolution
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Example 12.5esistance of a metal wire of length 1 m is 26 Ί at 20 C. If thediameter of thewire is 0.3 mm, what will be the resistivity of themetal at that temperature? Using Table 12.2, predict the materlalof the wire. |
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Answer» Resistance , R = 26Ω Length of wire , L = 1m diameter of circular part of wire ,d = 0.3mm = 0.3 × 10⁻³m so, base area of wire , A = πr² = πd²/4 [ ∵d = 2r] = 3.14 × (0.3 × 10⁻³)²/4m²= 3.14 × 9 × 10⁻⁸/4 m² = 28.26/4 × 10⁻⁸ m² = 7.06 × 10⁻⁸ m² Now, use formula, R = ρL/A Here, R is the resistance, ρ is the resistivity , L is the length of wire and A is the base area of it .So , ρ = RA/L = 26Ω × 7.06 × 10⁻⁸m²/1mρ = 1.8356 × 10⁻⁶ Ωm Hence, resistivity is 1.8356 × 10⁻⁶ Ωm at 20°C |
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