Find the potential difference between $a$ and $b$,as shown in the below circuit. (in $V$)

Two batteries of e.m.f $4 \text{ V}$ and $8 \text{ V}$ with internal resistance $1 \Omega$ and $2 \Omega$ respectively are connected in a circuit with a resistance of $9 \Omega$ as shown in the figure. The current and potential difference between the points $P$ and $Q$ is

The figure shows a network of resistances in which the point $A$ is earthed. The current through the $3\,\Omega$ resistor is

In the circuit shown, the heat produced in $5 \Omega$ resistance due to current $I_2$ is $50 \text{ J/s}$. Then, the heat generated per second in $2 \Omega$ resistance is (in $\text{ J/s}$)

In the circuit shown,the resistance of the voltmeter is $10,000 \, \Omega$ and that of the ammeter is $20 \, \Omega$. The ammeter reading is $0.10 \, A$ and the voltmeter reading is $12 \, V$. Then $R$ is equal to ............. $\Omega$.

$A$ battery of $e.m.f.$ $10\, V$ is connected to a resistance network as shown in the figure. The potential difference ${V_A} - {V_B}$ between the points $A$ and $B$ is .................... $V$.