A carbon resistor is marked in coloured bands in the sequence blue, green, orange and gold. What is the resistance and tolerance value of the resistor?

The given graph shows the variation of resistance of mercury in the temperature range $\mathrm{O}< \mathrm{T}< 4\mathrm{K}.$ Name the phenomenon shown by the graph of figure.

$\mathrm{I}-\mathrm{V}$ graph for parallel and series combination of two metallic resistors are shown in figure. Which graph represents parallel combination? Justify your answer.

A set of $n$ identical resistors, each of resistance $R \mathrm{ohm}$, when connected in series have an effective resistance $X \mathrm{ohm}$ and when the resistors are connected in parallel, their effective resistance is $Y \mathrm{ohm}$. Find the relation between $R, X$ and $Y$.