$A$ battery is charged by a $15\,V$ battery for $8\,h$ at a current of $10\,A$. When this battery discharges, it provides a current of $5\,A$ for $15\,h$. The average terminal voltage during discharge is $14\,V$. What is the $watt-hour$ efficiency of this battery in $\%$?

$A$ $100 \ W$ bulb is rated at $200 \ V$ and a $200 \ W$ bulb is rated at $100 \ V$. Then:

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

$A$ fuse wire with radius $1\, mm$ blows at $1.5\, A$. The radius of the fuse wire of the same material to blow at $3\, A$ will be:

Column-$I$ gives certain physical quantities associated with the flow of current through a metallic conductor. Column-$II$ gives some mathematical relations involving electrical quantities. Match Column-$I$ and Column-$II$ with appropriate relations.

$A$. Mobility	$P$. $\frac{m}{ne^2 \rho}$
$B$. Electrical conductivity	$Q$. $neAv_{d}$
$C$. Relaxation period	$R$. $\frac{v_{d}}{E}$
$D$. Current	$S$. $\frac{J}{E}$

When a current is passed through water,acidified with a dilute sulphuric acid,the gases formed at the platinum electrodes are