Q32: An engineer needs a resistor with a zero overall tem- perature 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 P27.32 (page 828). The device must have an overall resistance of R1 + R2 = V independent of temperature and a uniform radius of r = 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 l1 and l2 of each segment. If not, explain.
Resistivities of carbon and Nichrome from Table 27.2:
ρ₁=
ρ₂=
Temperature coefficients of resistivity of carbon and Nichrome from Table( Table 27.2)
α₁=
α₂=