Cells in Series and Parallel

The situation shown in figure is equivalent to

Figure shows mixed grouping of identical cells each of $e.m.f. 4V$  and internal resistance $1\mathrm{\Omega }.$ This combination can be replaced by an equivalent cell between $A$ and $B$ having e.m.f. $E$ and internal resistance $r,$ where

Five cells each of emf $E$ and internal resistance $r$ are connected in series. Due to oversight one cell is connected wrongly. The equivalent internal resistance of the combination is

Three identical cells are connected in parallel across $AB.$ Net emf across $AB$ is

There are a large number of cells available, each marked $(6 \mathrm{V}, 0.5 \mathrm{\Omega })$ to be used to supply current to a device of resistance $0.75 \mathrm{\Omega },$ requiring $24$ Acurrent. How should the cells be arranged, so that power is transmitted to the load using minimum number of cells?

Two batteries of different emf and internal resistance are connected in series with an external load resistor. The current is $3.0 \mathrm{A}.$ When the polarity of one battery is reversed then, current becomes $1.0 \mathrm{A}.$ The ratio of the emf of the two batteries is

In the circuit shown in figure, all cells are ideal. The current through $2 \mathrm{\Omega }$ resistor is

Five cells each of emf $E$ and internal resistance $r$ are connected in series. If one cell is wrongly connected, then the equivalent emf of the combination is

Thousand cells of same emf $E$ and same internal resistance $r$ are connected in series in same order without an external resistance. The potential drop across $399$ cells is found to be

Figure shows mixed grouping of identical cells each of e.m.f. $4 \mathrm{V}$ and internal resistance $1\Omega$. This combination can be replaced by an equivalent cell between A and B having e.m.f. $E$ and internal resistance $r$, where