If the length of a wire is doubled, its specific resistance (resistivity) will be.......

$A$ cylindrical wire $P$ has resistance $10 \ \Omega$. $A$ second wire $Q$ has length and diameter half that of $P$. If the material of both the wires is same,then the resistance of wire $Q$ is (in $\Omega$)

$A$ uniform wire of resistance $R$ is uniformly compressed along its length,until its radius becomes $n$ times the original radius. Now,the resistance of the wire becomes:

Write the equation representing the relation between resistivity and temperature.

What is conductivity? On which factors does its value depend? Write its unit and dimension.

Why does the resistance of metallic conductors and semiconductors change differently with a change in temperature?