The figure shows a network of four resistors and three batteries. Which of the batteries is getting charged?

The potential difference $(V_A - V_B)$ between the points $A$ and $B$ in the given figure is (in $V$)

The current in the arm $CD$ of the circuit will be

Kirchhoff's second law is based on the law of conservation of:

Two batteries,one with an $emf$ of $3\,V$ and internal resistance $1\,\Omega$,and the other with an $emf$ of $15\,V$ and internal resistance $2\,\Omega$,are connected in series with a resistance $R$ as shown in the figure. If the potential difference between points $a$ and $b$ is zero,find the resistance $R$ in $\Omega$.

If a current of $7 \ A$ flows through the electric circuit,what is the potential difference between $B$ and $C$ in volts?