The temperature coefficient of resistivity of iron is 5.0 × 10−³ / °C; that of carbon is −0.50 × 10−³ / °C. When an iron wire and a carbon rod, each having the same 10 Ω resistance at 20°C, are cooled from that temperature to −80°C, the new ratio of the resistance of the carbon rod to the resistance of the iron wire at the lower temperature is A) −0.10. B) +1.9. C) +2.1. D) −10. E) +10.

Question

Quizplus · Accepted Answer

The resistance of iron increases with decreasing temperature, while the resistance of carbon decreases. Calculating the resistances at -80°C and finding their ratio gives approximately +2.1.

The Temperature Coefficient of Resistivity of Iron Is 5