The conductivity of a superconductor is.......

What is the resistivity of a perfect conductor?

The resistance of the bulb filament is $100 \ \Omega$ at a temperature of $100^{\circ} C$. If its temperature coefficient of resistance is $0.005 \ ^{\circ} C^{-1}$,at what temperature will its resistance become $200 \ \Omega$ (in $^{\circ} C$)?

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:

Assertion: Bending a wire does not affect electrical resistance.
Reason: Resistance of a wire is proportional to the resistivity of the material.

$A$ heating element has a resistance of $100\,\Omega$ at room temperature. When it is connected to a supply of $220\,V$,a steady current of $2\,A$ passes through it and the temperature is $500\,^{\circ}C$ higher than room temperature. What is the temperature coefficient of resistance of the heating element?