Question

A metal wire has a resistance of 8.00Ω at a temperature of 20C. If the same wire has a resistance of 8.40Ω at 70C, what is the resistance of this wire in ohms when its temperature is −10C?
R₀=8 Ω, T₀=20℃,
R₁=8.4 Ω, T₁=70℃,
T₂ = - 10℃
R₂=?
R=R₀[1-αΔT]
R₁=R₀[1-αΔT₁]
8.4=8[1+(70-20)α]
α={8.4/8 – 1)/50 = 10⁻³ K⁻¹
R₂=R₀[1-αΔT₂] =
=8[1+ 10⁻³•(-10-20)] =7.76 Ω

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