The graph showing the variation of resistance $(R)$ of a metal wire as a function of its diameter $(D)$,while keeping other parameters like length and temperature constant,is:

An electric wire of length $l$ and area of cross-section $a$ has a resistance $R \ \Omega$. Another wire of the same material having the same length and area of cross-section $4a$ has a resistance of:

Two conductors are made of the same material and have the same length. Conductor $A$ is a solid wire of diameter $1.0 \, mm$. Conductor $B$ is a hollow tube of outside diameter $2.0 \, mm$ and inside diameter $1.0 \, mm$. The resistance ratio $R_A/R_B$ will be

If a wire of resistance $R$ is melted and recasted to half of its length,then the new resistance of the wire will be

There are two wires of the same length and of the same material and radii $r$ and $2r$. The ratio of their specific resistance is

By increasing the temperature,the specific resistance of a conductor and a semiconductor respectively