The value of current in the $6 \,\Omega$ resistance is $....\,A$

The resistances in the Wheatstone bridge circuit shown in the diagram are all different,and the current through the galvanometer is zero. If all thermal effects are negligible,the current through the galvanometer will not be zero when:

In the part of a circuit shown in the figure,the potential difference $(V_G - V_H)$ between points $G$ and $H$ will be ............... $V$.

Two batteries $V_1$ and $V_2$ are connected to three resistors as shown below. If $V_1=2 \,V$ and $V_2=0 \,V$,then the current $I=3 \,mA$. If $V_1=0 \,V$ and $V_2=4 \,V$,then the current $I=4 \,mA$. Now,if $V_1=10 \,V$ and $V_2=10 \,V$,then the current $I$ will be ............ $\,mA$.

Three resistances $P, Q, R$ each of $2 \,\Omega$ and an unknown resistance $S$ form the four arms of a Wheatstone bridge circuit. When a resistance of $6 \,\Omega$ is connected in parallel to $S$,the bridge gets balanced. What is the value of $S$ in $\Omega$?

In the following circuit,the current $I_3$ is