$A$ metal wire of circular cross-section has a resistance $R_{1}$. The wire is now stretched without breaking, so that its length is doubled and the density is assumed to remain the same. If the resistance of the wire now becomes $R_{2}$, then $R_{2}: R_{1}$ is

Two metal wires of the same length and same area of cross-section have conductivities of their material $\sigma_1$ and $\sigma_2$. If they are connected in series,the effective conductivity is:

$A$ cylindrical conductor has a uniform cross-section. The resistivity of its material increases linearly from the left end to the right end. If a constant current is flowing through it and at a section at distance $x$ from the left end,the magnitude of the electric field intensity is $E$,which of the following graphs is correct?

The resistance of a coil is $4.2\, \Omega$ at $100\,^{\circ}C$ and the temperature coefficient of resistance of its material is $0.004\,^{\circ}C^{-1}$. Its resistance at $0\,^{\circ}C$ is ............. $\Omega$.

$A$ certain wire has a resistance $R$. The resistance of another wire identical with the first except having twice its diameter is (in $,R$)

$A$ metal wire has a resistance of $35 \,\Omega$. If its length is increased to double by drawing it,then its new resistance will be (in $\Omega$)