A coil of wire has a resistance of 37.1 W at 25.7 °C and 45.9 W at 55.7 °C. What

Question

A coil of wire has a resistance of 37.1 W at 25.7 °C and 45.9 W at 55.7 °C. What is the temperaturecoefficient of resistivity? I have: 45.9ohm=37.1ohm [1+30x] ....45.9ohm=37.1ohm(31x) x=0.0399 for the coefficient of resistivity but, it keepssaying that I am incorrect. A coil of wire has a resistance of 37.1 W at 25.7 °C and 45.9 W at 55.7 °C. What is the temperaturecoefficient of resistivity? I have: 45.9ohm=37.1ohm [1+30x] ....45.9ohm=37.1ohm(31x) x=0.0399 for the coefficient of resistivity but, it keepssaying that I am incorrect.

Explanation / Answer

Assume 37.1 ohms is the initial resistance and 45.9ohms is the final resistance. We apply the formula:    R(T)  = R(T0) X [ 1 + a(T - T0) We need to solve for a, which is the thermal coefficent ofresistivity 45.9 Ohms = 37.1 Ohms X [1 +a(55.7-25.7] 45.9 ohms = 37.1 + 1113a solve for a: we get that a = .007906

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