Assertion: The temperature dependence of resistance is usually given as, $R=R_0(1+\alpha ∆t)$. The resistance of a wire changes from $100$ $\mathrm{\Omega }$ to $150$ $\mathrm{\Omega }$ when its temperature is increased from ${27}^o \mathrm{C}$ to ${227}^o \mathrm{C}$. This implies that, $\alpha =2.5\times \frac{{10}^{–3}}{℃}$.

Reason: $R=R_0(1+\alpha ∆ t)$ is valid only when the change in the temperature, $∆T$, is small and, $∆R=(R–R_0)<<R_0$ .

$I$ and $V$ are respectively the current and voltage in a metal wire of resistance $R.$ The $I-V$ graph for the two different temperatures $T_1$ and $T_2$ are given, then

When the temperature of a conductor increases, the ratio of conductivity and resistivity _____

In an experiment, the resistance of a material is plotted as a function of temperature (in some range). As shown in the figure, it is a straight line.

One may conclude that