When the length and area of cross-section both are doubled,then its resistance

The graph showing the variation of resistance $(R)$ of a metal wire as a function of its diameter $(D)$,while keeping other parameters like length and temperature constant,is:

$A$ thick wire is stretched so that its length becomes two times. Assuming that there is no change in its density,what is the ratio of the change in resistance of the wire to the initial resistance of the wire?

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 wires $A$ and $B$ are made up of the same material and have the same mass. Wire $A$ has a radius of $2.0 \ mm$ and wire $B$ has a radius of $4.0 \ mm$. The resistance of wire $B$ is $2 \ \Omega$. The resistance of wire $A$ is . . . . . . $\Omega$.

As the temperature of a conductor increases,its resistivity and conductivity change. The ratio of resistivity to conductivity