Write dimensional formula of electrical conductivity.

If the current supplied to a variable resistor is constant, draw a graph between voltage and resistance.

$I$-$V$ graph for a metallic wire at two different temperatures, $T_1$ and $T_2$ is as shown in Fig. 3.256. Which of the two temperatures is lower and why?

The $V$-$I$ graphs of two resistors, and their series combination, are shown in Fig. Which one of these graphs represents the series combination of the other two? Give reasons for your answer.

$V-I$ graphs for parallel and series combination of two metallic resistors are as shown in Fig. Which graph represents parallel combination? Justify your answer.

The voltage-current variation of two metallic wires $X$ and $Y$ at constant temperature are shown in Fig. Assuming that the wires have the same length and the same diameter, explain which of the two wires will have larger resistivity.

The voltage-current graphs for two resistors of the same material and the same radii with lengths $L_1$ and $L_2$ are shown in Fig. If $L_1>L_2$, state with reason, which of these graphs represents voltage-current change for $L_1$.