If graph shown in figure represents the $V-I$ characteristic of a device. Identify the region, if any, over which this device has a negative resistance.

The current voltage graphs for a given metallic wire at two different temperatures ${\mathrm{T}}_1$ and ${\mathrm{T}}_2$ are shown in Fig. The temperature ${\mathrm{T}}_2$ is greater than temperature ${\mathrm{T}}_1.$ State whether this statement is true or false, giving reasons in brief to support of your answer.

Draw graphs to show the variation of resistance of a metal as a function of the diameter, keeping length and temperature constant.

How a battery is to be connected so that the shown rheostat in Figure. Will behave like a potential divider? Also indicate the points about which output can be taken.

Why is a potentiometer preferred over a voltmeter for determining the emf of a cell?

A cell of emf $\left(\epsilon \right)$ and internal resistance $\left(\mathrm{r}\right)$ is connected across a variable external resistance $\left(\mathrm{R}\right)$. Plot graphs to show variation of  $\epsilon$ with $\mathrm{R}$.