What equal length of an iron wire and a copper-nickel alloy wire, each of $2 \mathrm{mm}$ diameter connected parallel to give an equivalent resistance of $3 \mathrm{\Omega }$?
(Given resistivities of iron and copper-nickel alloy wire are $12 \mathrm{\mu \Omega } \mathrm{cm}$ and $51 \mathrm{\mu \Omega } \mathrm{cm}$ respectively)

Calculate the amount of charge on capacitor of $4 \mathrm{\mu F}.$ The internal resistance of battery is $1\mathrm{\Omega }:$

The colour coding on a carbon resistor is shown in the given figure. The resistance value of the given resistor is:

The ratio of the equivalent resistance of the network (shown in figure) between the points $a$ and $b$ when switch is open and switch is closed is $x: 8$. The value of $x$ is