Problem 2: A carbon electrode has a resistance of 0.125 at 20oC.The temperature coefficient of carbon is -0.0005 at 20oC. What will be the resistance of electrode at 85oC?
Given R1 = 0.125 t1 = 20oC
α = -0.0005 K-1 t2= 85oC
Required R2 =?
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 = 65oC. Therefore, use the above formula to find the resistance of carbon at 85oC.
Thus there is a slight decrease in the resistance of carbon.