College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 19

An engineer needs a resistor with a zero overall temperature coefficient of resistance at 20.0°C. She designs a pair of circular cylinders, one of carbon and one of Nichrome as shown in Figure P17.30. The device must have an overall resistance of R 1 + R 2 = 10.0 independent of temperature and a uniform radius of r = 1.50 mm. Ignore thermal expansion of the cylinders and assume both are always at the same temperature. (a) Can she meet the design goal with this method (b) If so, state what you can determine about the lengths L 1 and L 2 of each segment. If not, explain.