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A nichrome heating element has resistance 75.3 Ω at 27°C. On a 230 V supply it settles to a steady current of 2.68 A (α = 1.7×10⁻⁴ °C⁻¹). Its steady temperature is about:
A300 °C
B820 °C
C420 °C
D847 °C
Answer & Solution
Correct answer: D. 847 °C
R₂ = 230/2.68 = 85.8 Ω. From R₂ = R₁[1 + αΔT], ΔT = (85.8 − 75.3)/(75.3×1.7×10⁻⁴) ≈ 820 °C, so T₂ ≈ 820 + 27 = 847 °C.
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