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

The resistance of an incandescent lamp is

The $I-V$ graph for a conductor at two different temperatures $100^{\circ} C$ and $400^{\circ} C$ is as shown in the figure. The temperature coefficient of resistance of the conductor is about (in per degree Celsius).

$A$ wire of radius $r$ has resistance $R$. If it is stretched to a radius of $\frac{3r}{4}$,its resistance becomes

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

The resistance of a wire at $0^{\circ} C$ is $20 \Omega$. If the temperature coefficient of resistance is $5 \times 10^{-3} {}^{\circ} C^{-1}$,the temperature at which the resistance will be double that at $0^{\circ} C$ is: (in $^{\circ} C$)