If $96500 \ C$ of charge deposits $1 \ g$ of a substance,how much time will it take to deposit $20 \ mg$ of copper from a copper sulfate solution using a current of $0.15 \ A$?

$A$ uniform metallic wire carries a current of $2\,A$ when a $3.4\,V$ battery is connected across it. The mass of the uniform metallic wire is $8.92 \times 10^{-3}\,kg$,its density is $8.92 \times 10^3\,kg/m^3$,and its resistivity is $1.7 \times 10^{-8}\,\Omega\cdot m$. The length of the wire is $l = \dots\dots\dots\dots\,m$.

In the given figure, the current through the $4 \, \Omega$ resistor is ................. $A$.

In the circuit shown in the figure,the resistances $R_1$ and $R_2$ are respectively:

In the circuit shown in the figure,switch $S_1$ is initially closed and $S_2$ is open. Find $V_a - V_b$ in $V$.

$A$ 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 ............ $^{\circ}C$.