$A$ wire is stretched to increase its length by $2\%$,then the percentage change in its resistance is . . . . . . . (in $\%$)

Why are alloys used for making standard resistance coils?

Explain how the resistance of a conductor depends on its dimensions.

The resistance of a wire is $5 \Omega$. Its new resistance in ohm,if stretched to $5$ times of its original length,will be:

$A$ $100 \ W$ tungsten light bulb has a resistance of $250 \ \Omega$ when it is turned $ON$ and $25 \ \Omega$ when turned $OFF$. The ambient room temperature is $25^{\circ} C$. Find the temperature of the filament when the bulb is turned $ON$. (Let $\alpha_{\text{tungsten}} = 4.5 \times 10^{-3} /^{\circ} C$) (in $^{\circ} C$)

Why does the resistivity of a metal increase with an increase in temperature,or why does its conductivity decrease with an increase in temperature?