Problem 2: A carbon electrode has a resistance of 0.125 at 20^{o}C.The temperature coefficient of carbon is -0.0005 at 20^{o}C. What will be the resistance of electrode at 85^{o}C?

Solution

Given R_{1} = 0.125 t_{1} = 20^{o}C

α = -0.0005 K^{-1} t_{2}= 85^{o}C

Required R_{2} =?

Strategy: Resistance of a substance depends upon the temperature. The relation is given by

∆t is the change in the temperature. Here in this case, ∆t = 85 – 20 = 65^{o}C. Therefore, use the above formula to find the resistance of carbon at 85^{o}C.

Thus there is a slight decrease in the resistance of carbon.

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