The resistance of a piece of rubber is higher than that of a piece of copper of the same dimensions.

The $V-I$ graphs for two resistors of the same material and the same radii with lengths $L_{1}$ and $L_{2}$ are shown below. If $L_{1} > L_{2}$, state with reason, which of these graphs represents voltage-current change for $L_{1}$?

Describe the nature of the $V-I$ graph for a nichrome wire. ($V =$ Potential difference,$I =$ Current)
$A$ metallic wire of $625 \, mm$ length offers a $4 \, \Omega$ resistance. If the resistivity of the metal is $4.8 \times 10^{-7} \, \Omega \cdot m$,calculate the cross-sectional area of the wire.

Two wires $A$ and $B$ are of the same metal,have the same area of cross-section,and have their lengths in the ratio $2:1$. What will be the ratio of currents flowing through them respectively,when the same potential difference is applied across each of them?

What is the symbol used to denote the unit of resistance,ohm?

What is the resistance of an electric arc lamp,if the lamp uses $20\, A$ when connected to a $220\, V$ line?