The resistance of a wire is $R$. If the length of the wire is doubled by stretching,then the new resistance will be

With an increase in temperature,the resistivity of a conductor ........ and the resistivity of a semiconductor ....... .

One $kg$ of copper is drawn into a wire of $1 \ mm$ diameter and a wire of $2 \ mm$ diameter. The resistance of the two wires will be in the ratio:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Alloys such as constantan and manganin are used in making standard resistance coils.
Reason $R:$ Constantan and manganin have a very small value of temperature coefficient of resistance.
In the light of the above statements, choose the correct answer from the options given below.

Consider four conducting materials: copper,tungsten,mercury,and aluminium with resistivity $\rho_{C}, \rho_{T}, \rho_{M}$,and $\rho_{A}$ respectively. Then:

Two wires of the same material have lengths $L$ and $2L$ and cross-sectional areas $4A$ and $A$ respectively. The ratio of their specific resistance would be