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 ........... $r$.

$A$ storage battery is connected to a charger for charging with a voltage of $12.5 \text{ V}$. The internal resistance of the storage battery is $1 \ \Omega$. When the charging current is $0.5 \text{ A}$,the $EMF$ of the storage battery is: ............... $\text{volts}$

What is a series connection of cells and what is a parallel connection of cells? Explain.

What is called the internal resistance of a cell?

The electromotive force of a primary cell is $2\,V$. When it is short-circuited,it gives a current of $4\,A$. Its internal resistance in $\Omega$ is:

Eight identical cells,each having an electromotive force $E$ and internal resistance $r$,are connected in series to form a closed circuit. An ideal voltmeter is connected across $2$ cells. The voltmeter will read ........ $E$.