Resistance of wire at $20°\mathrm{C}$ is $10 \mathrm{\Omega }$. At what temperature, resistance becomes $30 \mathrm{\Omega }$ (The temperature coefficient of resistance $\alpha =0.0125 °{\mathrm{C}}^{-1}$)

The figure shows graph between potential difference $\left(\mathrm{V}\right)$ and current $\left(\mathrm{I}\right)$ of a metallic wire at three different temperature ${\mathrm{T}}_1, {\mathrm{T}}_2$ and ${\mathrm{T}}_3$. Which of them will have the least value of temperature?

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Alloys such as constantan and manganin are used in making standard resistance coils.

Reason R: Constantan and manganin have very small value of temperature coefficient of resistance.

In the light of the above statements, choose the correct answer from the options given below.

$I$ 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

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