$A$ negligibly small current is passed through a wire of length $15 \; m$ and uniform cross-section $6.0 \times 10^{-7} \; m^{2},$ and its resistance is measured to be $5.0 \; \Omega .$ What is the resistivity of the material at the temperature of the experiment?

The lead wires should have

Consider four conducting materials: copper,tungsten,mercury,and aluminium with resistivity $\rho_{C}, \rho_{T}, \rho_{M}$,and $\rho_{A}$ respectively. Then:

When the temperature of a conductor increases, the ratio of conductivity and resistivity . . . . . . .

One $kg$ of copper is drawn into a wire of $1 \ mm$ diameter and a wire of $2 \ mm$ diameter. The resistance of the two wires will be in the ratio:

$A$ cylindrical resistor is connected to a battery with emf $5 \ V$. The resistance per unit length varies as $\rho(x) = \rho_0 \left(\frac{x}{L}\right)^\alpha$,where $\rho_0$ and $\alpha$ are constants and $x$ is the distance from one end of the resistor. The product $\rho_0 L$ is $10 \ \Omega$,where $L$ is the length of the resistor. If the thermal power generated by the resistor is $20 \ W$,then the value of $\alpha$ is: