an engineer needs a resistor with a zero overall temperature coefficient of resi

Question

an engineer needs a resistor with a zero overall temperature coefficient of resistance at 20 degrees Celsius. She designs a pair of circular cylinders, one of carbon and one of Nichrome. The device must have an overall resistance of R1+R2= 10.0 ohms independent of temperature and a uniform radius of r=1.5 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_ Is so, state what you can determine about the lengths L1 and L2 of each segment. If not, explain.

Explanation / Answer

we know, R = pl/A here, A1 = A2 = pi* (1.50 mm) ^ 2 and R1 + R2 = 10 R1 = p1 * l1 / A1 R2 = p2 * l2/ A2 if you know the resistivity of the materials, p1 and p2, then you can calculate the ratio of l1 and l2 from these equations. To get their exact value, you will need more data. Hope this was helpful

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