The current inside a copper voltameter:

Find the potential difference between $a$ and $b$,as shown in the below circuit. (in $V$)

The potential difference between the points $P$ and $Q$ is nearly: (in $V$)

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

Inside a superconducting ring,six identical resistors each of resistance $R$ are connected as shown in the figure. Imagine a battery of $emf$ $E$ connected between points $O$ and $1$,with its positive terminal connected to $O$.

$A$ current of $2.0 \, A$ passes through a cell of $e.m.f.$ $1.5 \, V$ having an internal resistance of $0.15 \, \Omega$. The potential difference measured,in $volts$,across the terminals of the cell will be: