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 temperature coefficient of resistance of a resistor wire is $0.00125\,^{\circ}C^{-1}$. At $300\,K$,its resistance is $1\,\Omega$. At what temperature in $K$ will its resistance be $2\,\Omega$?

Given below are two statements:
Statement $I$: The resistivity of a conductor is independent of its temperature.
Statement $II$: The resistivity of a semiconductor decreases with an increase in temperature.
Select the correct option.

$n$ conducting wires of same dimensions but having resistivities $1, 2, 3, . . . , n$ are connected in series. The equivalent resistivity of the combination is

The lead wires should have

$A$ copper wire is stretched to make it $0.5\%$ longer. The percentage change in its electric resistance if its volume remains unchanged is ................ $\%$