The figure below shows currents in a part of an electric circuit. The current $i$ is ............. $A$.

The reading of the ammeter in amperes for the following circuit is:

In the case of a Wheatstone bridge,the balanced condition is.....

Four resistances of $15\, \Omega, 12\, \Omega, 4\, \Omega$ and $10\, \Omega$ are connected in cyclic order to form a Wheatstone bridge network. The resistance that is to be connected in parallel with the resistance of $10\, \Omega$ to balance the network is ................. $\Omega$.

Two ideal batteries of emf $V_1$ and $V_2$ and three resistances $R_1, R_2$ and $R_3$ are connected as shown in the figure. The current in resistance $R_2$ would be zero if:
$(A)$ $V_1=V_2$ and $R_1=R_2=R_3$
$(B)$ $V_1=V_2$ and $R_1=2R_2=R_3$
$(C)$ $V_1=2V_2$ and $2R_1=2R_2=R_3$
$(D)$ $2V_1=V_2$ and $2R_1=R_2=R_3$

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 $.5$)