A uniform wire of resistance $R$ is stretched uniformly $n$ times and then, cut to form five identical wires. These wires are arranged as shown in the figure. The effective resistance between $A$ and $B$ will be, 

 

Assertion :- Resistivity of metals decreases with decrease in temperature but have some finite value as the temperature approaches absolute zero.

Reason :- The residual resistivity near absolute zero is caused primarily by the collision of electrons with impurities and imperfections in the metal.

The temperature coefficient of resistance of a wire is $0.00125$ per degree Celsius. At $300 \mathrm{K}$ its resistance is $1 \mathrm{ohm}$. The resistance of the wire will be $2 \mathrm{ohm}$ at a temperature:-

Assertion :- The value of temperature coefficient of resistance is positive for metals.

Reason :- The value of temperature coefficient of resistance is negative for insulators.