The value of the internal resistance of an ideal cell is:

Two identical cells each of emf $E$ and internal resistance $r$ are connected in parallel with an external resistance $R$. To get maximum power developed across $R$,the value of $R$ is

When can the internal resistance of a cell be neglected? Explain.

Explain cell,emf,and internal resistance. Derive the relation between potential difference,emf,and internal resistance.

An energy source will supply a constant current into the load if its internal resistance is

Two batteries of different $e.m.f.$ values and internal resistances are connected in series with each other and with an external load resistor. The current is $3.0 \,A$. When the polarity of one battery is reversed,the current becomes $1.0 \,A$. The ratio of the $e.m.f.$ values of the two batteries is ............