A group of $N$ cells, whose emf varies directly with the internal resistance as per the equation $E_N=1.5 r_N$, are connected as shown in the figure. The current $I$ in the circuit is

Two cells of emf $10 \mathrm{V}$ and $15 \mathrm{V}$ are connected in parallel to each other between points $A$and $B$. The cell of emf $10 \mathrm{V}$ is ideal but the cell of emf $15 \mathrm{V}$ has an internal resistance $1 \mathrm{\Omega }$. The equivalent emf between $A$and $B$ is

Two batteries, one of emf $18 \mathrm{V}$ and internal resistance $2 \mathrm{\Omega }$ and the other of emf $12 \mathrm{V}$ and internal resistance $1 \mathrm{\Omega }$ are connected, as shown in the figure. Voltmeter $V$ will record a reading of

The figure shows a network of currents. Study the diagram and find the magnitude of current $I$.