What is the change in the resistance of a telegraph line from winter to summer if it it is composed of an iron conductor 10 mm2 in cross-section? The temperature changes from —30°C to +30°C. The length of the conductor in winter is 100 km. The resistivity of iron in the winter is 8.7 X 10-6Ωcm; the temperature coefficient is 6 x 10-3/°C. How will the result change if the increase in length of the conductor as a result of the rise in temperatures is taken into account. The coefficient of linear expansion of iron is 12 X 10- 6/°C
