For the circuits $A$ and $B$ as shown in the figure,identify the correct option.

$A$ thermocouple of resistance $1.6\,\Omega$ is connected in series with a galvanometer of $8\,\Omega$ resistance. The thermocouple develops an e.m.f. of $10\,\mu V$ per degree temperature difference between two junctions. When one junction is kept at $0\,^{\circ}C$ and the other in a molten metal,the galvanometer reads $8\,mV$. The temperature of the molten metal,when e.m.f. varies linearly with temperature difference,will be ............ $^{\circ}C$.

If the heat produced in the $5 \, \Omega$ resistor is $10 \, \text{cal/sec}$, then how much heat in $\text{cal/sec}$ is produced in the $4 \, \Omega$ resistor?

$A$ current of $2\,A$ flows through a $2\,\Omega$ resistor when connected across a battery. The same battery supplies a current of $0.5\,A$ when connected across a $9\,\Omega$ resistor. The internal resistance of the battery is:

If the rheostat slider were to move from the extreme right to the far left,how will the reading of voltmeter $V_1$ change?

Two resistances of $400 \Omega$ and $800 \Omega$ are connected in series with a $6 \text{ V}$ battery of negligible internal resistance. $A$ voltmeter of resistance $10000 \Omega$ is used to measure the potential difference across the $400 \Omega$ resistor. The error in the measurement of potential difference in volts is approximately: