Two wires of the same dimensions but resistivities $\rho_1$ and $\rho_2$ are connected in series. The equivalent resistivity of the combination is

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:

The $I-V$ graph for a conductor at two different temperatures $100^{\circ} C$ and $400^{\circ} C$ is as shown in the figure. The temperature coefficient of resistance of the conductor is about (in per degree Celsius).

Resistance of a wire at $0^{\circ} C, 100^{\circ} C$ and $t^{\circ} C$ is found to be $10 \Omega, 10.2 \Omega$ and $10.95 \Omega$ respectively. The temperature $t$ in Kelvin scale is $\qquad$

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

The resistance of a $5\, cm$ long wire is $10\, \Omega$. It is uniformly stretched so that its length becomes $20\, cm$. The resistance of the wire is ............. $\Omega$.