For an open circuit condition,what is the value of the terminal voltage of a cell?

In the following circuit, the current through $6 \Omega$ resistor is

Four cells, each of emf $E$ and internal resistance $r$, are connected in series across an external resistance $R$. By mistake, one of the cells is connected in reverse. Then the current in the external circuit is

The potential difference in open circuit for a cell is $2.2\, V$. When a $4\, \Omega$ resistor is connected between its two electrodes,the potential difference becomes $2\, V$. The internal resistance of the cell will be .............. $\Omega$.

$A$ battery of $e.m.f.$ $2\,V$ and internal resistance $0.1\, \Omega$ is being charged by a current of $5\,A$. The potential difference across the terminals of the battery is ......... $V$.

When a battery is connected across a resistor of $16 \Omega$,the voltage across the resistor is $12 \ V$. When the same battery is connected across a resistor of $10 \Omega$,the voltage across it is $11 \ V$. The internal resistance of the battery in ohm is