V−I graph for conductor at temperature T1 and T2 is shown in the figure.
We know that resistance of a conductor is directly proportional to its temperature. Hence, R1∝T1⇒tanθ∝T1 ⇒tanθ=KT1.....(i) and R2∝T2 ⇒tan(90∘−θ)∝T2 ⇒cotθ∝T2 ⇒cotθ=KT2 ....(ii) ∴ From Eqs. (i) and (ii), we get KT2−KT1=cotθ−tanθ K(T2−T1)=