When a battery is connected across a resistor of $16 \Omega$,the voltage across the resistor is $12 \ V$. When the same battery is connected across a resistor of $10 \Omega$,the voltage across it is $11 \ V$. The internal resistance of the battery in ohm is

When two cells of emfs $E_1$ and $E_2$ and different internal resistances $r_1$ and $r_2$ are connected in series with an external load resistor $R$,the current through the load is $5 \ A$. If the polarity of the cell of emf $E_2$ is reversed,then the current through the load is $2 \ A$. Then $\frac{E_1}{E_2} = $

$n$ identical cells,each of emf $E$ and internal resistance $r$,are joined in series to form a row. $m$ such rows are joined in parallel across a load resistance $R$. The current in each cell is:

An electric eel generates an electric current using biological cells called electroplaques. The eel has a total of $5000$ electroplaques arranged in $100$ rows. This arrangement is shown in the figure. Each electroplaque has an $emf$ of $0.15\ V$ and an internal resistance of $0.25\ \Omega$. The water surrounding the eel completes the circuit between its head and tail. If the resistance of the water is $500\ \Omega$,the electric current generated by the eel in the water is .......... $A$.

Two cells of equal $e.m.f.$ $E$ and internal resistances $r_1$ and $r_2$ $(r_1 > r_2)$ are connected in series. On connecting this combination to an external resistance $R$,it is observed that the potential difference across the first cell becomes zero. The value of $R$ will be

$A$ student is given $4$ identical batteries having $EMF$ $1.5 \ V$ each and internal resistance of $0.1 \ \Omega$ each. The student is asked to connect them in an assisting manner. By mistake,he connects $1$ battery in reverse way. The resultant $EMF$ and resultant internal resistance offered by the combination is . . . . . . .