$A$ battery of emf $12 \text{ V}$ and internal resistance $4 \Omega$ is connected to a resistor. If the current in the circuit is $0.8 \text{ A}$,then the resistance of the resistor is: (in $\Omega$)

$A$ fuse wire of radius $0.2 \,mm$ blows off with a current of $5 \,A$. The fuse wire of the same material but of radius $0.3 \,mm$ will blow off with a current of:

$A$ $16 \ \Omega$ wire is bent to form a square loop. $A$ $9 \ V$ battery with internal resistance $1 \ \Omega$ is connected across one of its sides. If a $4 \ \mu F$ capacitor is connected across one of its diagonals,the energy stored by the capacitor will be $\frac{x}{2} \ \mu J$,where $x = . . . . . . .$

$A$ thermocouple is formed by two metals $X$ and $Y$. Metal $X$ comes earlier than $Y$ in the Seebeck series. If the temperature of the hot junction increases beyond the temperature of inversion,then the direction of the current in the thermocouple will be:

$A$ current of $2 \, A$ flows in an electric circuit as shown in the figure. The potential difference $(V_R - V_S)$, in volts ($V_R$ and $V_S$ are potentials at $R$ and $S$ respectively) is:

$A$ student connects a voltmeter,ammeter,and resistance according to the circuit given. If the voltmeter reading is $20\, V$ and the ammeter reading is $4\, A$,then the resistance $R$ will be: