$V-i$ graphs for parallel and series combination of two identical resistors are as shown in the figure. Which graph represents the parallel combination?

The equivalent resistance between points $A$ and $B$ in the given network is ............ $\Omega$.

$A$ wire has resistance $12\,\Omega$. It is bent in the form of a circle. The effective resistance between the two points on any diameter is equal to ................ $\Omega$.

The equivalent resistance across $A$ and $B$ as shown in the figure is ............. $\Omega$.

You are given several identical resistances each of value $R = 10\,\Omega$ and each capable of carrying a maximum current of $1\,A$. It is required to make a suitable combination of these resistances to produce a resistance of $5\,\Omega$ which can carry a current of $4\,A$. The minimum number of resistances of the type $R$ that will be required for this job is:

Resistance $n$,each of $r \ \Omega$,when connected in parallel give an equivalent resistance of $R \ \Omega$. If these resistances were connected in series,the combination would have a resistance in $\Omega$,equal to