$A$ battery is charged at $15\,V$ for $8\,h$ with a current of $10\,A$. During discharge, the battery supplies a current of $5\,A$ for $15\,h$. The terminal voltage during discharge is $14\,V$. Find the watt-hour efficiency of the battery in percentage.

$A$ wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to current,the temperature of the wire is raised by $\Delta T$ in a time $t$. $A$ number $N$ of similar cells is now connected in series with a wire of the same material and cross-section but of length $2L$. The temperature of the wire is raised by the same amount $\Delta T$ in the same time $t$. The value of $N$ is

$A$ galvanometer $(G)$ of $2 \ \Omega$ resistance is connected in the given circuit. The ratio of charge in $C_1$ $(4 \ \mu F)$ and $C_2$ $(6 \ \mu F)$ is:

In the circuit diagram shown in the figure below, the current flowing through the resistance $3\, \Omega$ is $\frac{x}{3}\, A$. The value of $x$ is $...........$

$A$ thermocouple is made of $Cu$ and $Fe$. If a battery is connected in it,then

$A$ cable consists of a copper wire of radius $9 \, mm$ having a resistance of $5 \, \Omega$. If this cable is replaced by $6$ copper wires each of radius $3 \, mm$,what will be the new resistance of the cable in $\Omega$?