The resistance of a wire is $R$. It is bent at the middle by $180^o$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is

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

Three copper wires of lengths and cross-sectional areas are $(l, A)$,$(2l, A/2)$,and $(l/2, 2A)$. Resistance is minimum in

The resistivity of iron is $1 \times 10^{-7} \, \Omega \cdot m$. The resistance of an iron wire of a particular length and thickness is $1 \, \Omega$. If the length and the diameter of the wire are both doubled, then the resistivity in $\Omega \cdot m$ will be:

$A$ strip of copper and another of germanium are cooled from room temperature to $80\, K$. The resistance of

The external diameter of a $5 \, m$ long hollow tube is $0.1 \, m$ and the thickness of its wall is $0.005 \, m$. If the resistivity $\rho = 1.7 \times 10^{-8} \, \Omega \cdot m$, then its resistance will be: