$A$ wire of resistance $x \ \Omega$ is drawn out,so that its length is increased to twice its original length,and its new resistance becomes $20 \ \Omega$. Then $x$ will be ........ $\Omega$.

$A$ 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 variation of applied potential and current flowing through a given wire is shown in the figure. The length of the wire is $31.4 \, cm$. The diameter of the wire is measured as $2.4 \, cm$. The resistivity of the given wire is measured as $x \times 10^{-3} \, \Omega \cdot cm$. The value of $x$ is . . . . . . [Take $\pi = 3.14$]

Constantan wire is used in making standard resistances because its

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 ............. $\Omega$.

Two wires $A$ and $B$ are made up of the same material and have the same mass. Wire $A$ has a radius of $2.0 \ mm$ and wire $B$ has a radius of $4.0 \ mm$. The resistance of wire $B$ is $2 \ \Omega$. The resistance of wire $A$ is . . . . . . $\Omega$.