$A$ resistance $R$ is stretched to four times its length. Its new resistance will be

$I-V$ 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

$A$ $1\,m$ long wire is broken into two unequal parts $X$ and $Y$. The $X$ part of the wire is stretched into another wire $W$. The length of $W$ is twice the length of $X$ and the resistance of $W$ is twice that of $Y$. Find the ratio of the length of $X$ to the length of $Y$.

Wires $P$ and $Q$ have the same resistance at ordinary (room) temperature. When heated,the resistance of $P$ increases and that of $Q$ decreases. We conclude that:

Two metal wires of identical dimensions are connected in series. If $\sigma_1$ and $\sigma_2$ are the conductivities of the metal wires respectively,the effective conductivity of the combination is

What is the resistance of a cubic block of length $50 \, cm$ having a resistivity of $50 \times 10^{-8} \, \Omega m$?