$A$ battery with an internal resistance of $4 \Omega$ is connected to a circuit consisting of three resistors,$R$,$2R$,and $4R$,as shown in the figure. If the power generated in the circuit is maximum,then the magnitude of $R$ must be: (in $\Omega$)

Four ammeters with identical internal resistance $r$ and a resistor $R$ are connected to a current source as shown. If the readings of $A_1$ and $A_2$ are $3 \, A$ and $5 \, A$ respectively,then the reading of $A_4$ is ............. $A$.

$A$ uniform wire of resistance $9 \, \Omega$ is cut into $3$ equal parts. They are connected in the form of an equilateral triangle $ABC$. $A$ cell of $e.m.f.$ $2 \, V$ and negligible internal resistance is connected across $B$ and $C$. The potential difference across $AB$ is ............... $V$.

In the circuit shown,the currents $i_{1}$ and $i_{2}$ are

In the adjoining circuit shown,the potential difference between points $A$ and $B$ will be:

In the given circuit,an ideal voltmeter connected across the $10\,\Omega$ resistance reads $2\,V$. The internal resistance $r$ of each cell is ................... $\Omega$.