The figure shows currents in a part of an electric circuit. Then the current $I$ is: (in $A$)

Four ammeters with identical internal resistances $r$ and a resistor of resistance $R$ are connected to a current source as shown in the figure. It is known that the reading of the ammeter $A_1$ is $I_1 = 3\ A$ and the reading of the ammeter $A_2$ is $I_2 = 5\ A$. Determine the ratio of the resistances $R/r$.

If ${V_{AB}} = 4\,V$ in the given figure,then resistance $X$ will be .............. $\Omega$.

$A$ Wheatstone bridge is initially at room temperature and all arms of the bridge have the same value of resistance $(R_1=R_2=R_3=R_4=R)$. When $R_3$ is heated to some temperature, its resistance value increases by $10 \%$. The potential difference $(V_a - V_b)$ (after $R_3$ is heated) is . . . . . . $V$. Given the total voltage is $40 \text{ V}$.

In the circuit shown,$E_1 = 4.0 \ V, R_1 = 2 \ \Omega, E_2 = 6.0 \ V, R_2 = 4 \ \Omega$ and $R_3 = 2 \ \Omega$. The current $I_1$ is : ................ $A$

In the given circuit,if no current flows through the ammeter,what is the value of $X$ in $\Omega$?