In the given electrical circuit,which one of the following equations is correct?

For the circuit shown in the figure,the current through the $6 \Omega$ resistor connected between the junctions $A$ and $B$ is (in $A$)

In a Wheatstone bridge,three resistances $P, Q$ and $R$ are connected in the three arms and the fourth arm is formed by two resistances $S_1$ and $S_2$ connected in parallel. The condition for the bridge to be balanced is

In the following diagram,the Wheatstone bridge is balanced when we interchange the resistances of:

If the internal resistance of the battery is $1\, \Omega$, then what is the reading of the ammeter?

In a Wheatstone bridge (see figure),resistances $P$ and $Q$ are approximately equal. When $R = 400 \,\Omega$,the bridge is balanced. On interchanging $P$ and $Q$,the value of $R$ for balance is $405 \,\Omega$. The value of $X$ is close to ................. $\Omega$. (in $.5$)