In which of the above cells, the potential difference between the terminals of a cell exceeds its emf.

Find the current flowing through the resistance $R_1$ of the circuit shown in figure if the resistances are equal to $R_1=10 \mathrm{\Omega }, R_2=20 \mathrm{\Omega }$ and $R_3=30 \mathrm{\Omega }$ and the potentials of points $1, 2$ and $3$ are equal to ${\mathrm{\phi }}_1=10 \mathrm{V}, {\mathrm{\phi }}_2=6 \mathrm{V}$ and ${\mathrm{\phi }}_3=5 \mathrm{V}$.

In the circuit shown in figure if the resistances are equal to $R_1=10 \mathrm{\Omega }, R_2=20 \mathrm{\Omega }$, and $R_3=30 \mathrm{\Omega }$, and the potentials of points $1, 2$ and $3$ are equal to ${\mathrm{\phi }}_1 = 10 \mathrm{V}, {\mathrm{\phi }}_2 = 6 \mathrm{V},$ and ${\mathrm{\phi }}_3 = 5 \mathrm{V}$.

In the figure, a part of circuit is shown:

In the shown circuit, what is the potential difference across $A$ and $B$.