In the circuit shown below,the cell has an $e.m.f.$ of $10\,V$ and internal resistance of $1\,\Omega$. The other resistances are shown in the figure. The potential difference ${V_A} - {V_B}$ is ................ $V$.

For the circuit shown in the figure,the power delivered by the battery is ................ $W$.

Find the ratio of currents as measured by the ammeter in two cases: when the key $K$ is open and when the key $K$ is closed.

$A$ wire of cross-section area $A$,length $L_1$,resistivity $\rho_1$ and temperature coefficient of resistivity $\alpha_1$ is connected to a second wire of length $L_2$,resistivity $\rho_2$,temperature coefficient of resistivity $\alpha_2$ and the same area $A$,so that the wires carry the same current. The total resistance $R$ is independent of temperature for small temperature changes if (Thermal expansion effect is negligible):

In the given circuit,the internal resistance of the $18\,V$ cell is negligible. If $R_1 = 400\,\Omega$,$R_3 = 100\,\Omega$,and $R_4 = 500\,\Omega$,and the reading of an ideal voltmeter across $R_4$ is $5\,V$,then the value of $R_2$ will be ........... $\Omega$.

In the given figure,the steady state current $I$ is ................. $A$.