I–V graph for a metallic wire at two different temperatures, T1 and T2, is shown in the figure. Which of the two temperatures is lower and why?

Slope of a V-I graph gives the value of 1/R, as we can see that the slope of graph 1 is greater than graph 2, so 1/R1 > 1/R2 or R2 > R1. We know that the resistance of metals increases with an increase in temperature; therefore, T2 > T1. It means T1 is lower because R1 is smaller.