Which of the following graphs represents the variation of resistivity ( $\rho$ ) with temperature $(T)$ for copper?

The resistance of a wire is $20 \Omega$. It is stretched,so that the length becomes three times,then the new resistance of the wire will be (in $\Omega$)

$A$ rectangular parallelopiped is measured as $1\,cm \times 1\,cm \times 100\,cm$. If its specific resistance is $3 \times 10^{-7}\,\Omega\,m$,then the resistance between its two opposite rectangular faces (as shown in the figure) will be $.......... \times 10^{-7} \Omega$.

Assertion: Bending a wire does not affect electrical resistance.
Reason: Resistance of a wire is proportional to the resistivity of the material.

Arrange the following materials in increasing order of their resistivity: Nichrome,Copper,Germanium,Silicon.

The following figure shows cross-sections through three long conductors of the same length and material,with square cross-sections of edge lengths as shown. Conductor $B$ will fit snugly within conductor $A$,and conductor $C$ will fit snugly within conductor $B$. The relationship between their end-to-end resistance is: