The unit of $e.m.f.$ is

The figure shows a circuit having eight resistances of $1 \Omega$ each,labelled $R_1$ to $R_8$,and two ideal batteries with voltages $\varepsilon_1=12 V$ and $\varepsilon_2=6 V$. Which of the following statement$(s)$ is(are) correct?
$(A)$ The magnitude of current flowing through $R_1$ is $7.2 A$.
$(B)$ The magnitude of current flowing through $R_2$ is $1.2 A$.
$(C)$ The magnitude of current flowing through $R_3$ is $4.8 A$.
$(D)$ The magnitude of current flowing through $R_5$ is $2.4 A$.

$A$ battery of $3.0 \ V$ is connected to a resistor dissipating $0.5 \ W$ of power. If the terminal voltage of the battery is $2.5 \ V$,the power dissipated within the internal resistance is $....... \ W$.

$A$ galvanometer of resistance $G$ is connected in a circuit. Now,a resistance $R$ is connected in series with the galvanometer. To keep the main current in the circuit unchanged,the resistance $S$ to be put in parallel with the series combination of $G$ and $R$ is:

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

In the given circuit, the current flowing through the resistance $20 \, \Omega$ is $0.3 \, A$, while the ammeter reads $0.8 \, A$. What is the value of $R_1$ in $\Omega$?