$A$ battery consists of a variable number $n$ of identical cells,each having electromotive force $E$ and internal resistance $r$,connected in series. The terminals of the battery are short-circuited,and the current $I$ is measured. Which one of the graphs below shows the relationship between $I$ and $n$?

Two cables of copper are of equal lengths. One of them has a single wire of area of cross-section $A$, while the other has $10$ wires of cross-sectional area $A / 10$ each. Determine their suitability for transporting $A.C.$ and $D.C.$

For the circuit shown in the figure:
$(A)$ The current $I$ through the battery is $7.5 \text{ mA}$.
$(B)$ The potential difference across $R_L$ is $18 \text{ V}$.
$(C)$ The ratio of powers dissipated in $R_1$ and $R_2$ is $3$.
$(D)$ If $R_1$ and $R_2$ are interchanged,the magnitude of the power dissipated in $R_L$ will decrease by a factor of $9$.

$A$ cell of emf $E$ has an internal resistance $r$ and is connected to a rheostat. When the resistance $R$ of the rheostat is changed,which is the correct graph of the potential difference $V$ across it?

The Peltier coefficient is $2 \times 10^{-9} \, V$. How much heat in $ergs$ is produced when a current of $2.5 \, A$ is passed for $2 \, minutes$?

If two wires having resistance $R$ and $2R$ are joined in series and then in parallel,what is the ratio of heat generated in these two situations,assuming the same voltage is applied?