Consider a simple circuit shown in figure stands for a variable resistance $R^{\text{'}}$. $R^{\text{'}}$ can vary from $R_0$ to infinity, $r$ is internal resistance of the battery $\left(r<<R<<R^{\text{'}}\right)$.

The following figures show four situations, in which positive and negative charges move horizontally through a region and give the rate at which each charge moves. Rank the situations according to the effective current through the region greatest first.

Variation of current passing through a conductor as the voltage applied across its ends as varied is shown in the adjoining diagram. If the resistance $\left(R\right)$ is determined at the points $A, B, C$ and $D$, we will find that

$I-V$ characteristic of a copper wire of length $L$ and area of cross-section $A$ is shown in the figure. The slope of the curve becomes

The resistance $R_t$ of a conductor varies with temperature $t$ as shown in the figure. If the variation is represented by $R_t=R_0\left[1+\alpha t+\beta t^2\right]$, then

The $V-i$ graph for a conductor at temperature $T_1$ and $T_2$ are as shown in the figure. $\left(T_2-T_1\right)$ is proportional to