The emfs of three cells connected in parallel are $E_1=5 \ V, E_2=8 \ V$ and $E_3=10 \ V$ and their internal resistances are $r_1=1 \ \Omega, r_2=2 \ \Omega$ and $r_3=3 \ \Omega$,respectively. By changing $E_3$ to $E_{3N}$,the equivalent emf is doubled. Then $E_{3N}$ in $V$ is:

Two identical cells each of emf $1.5 \,V$ are connected in parallel across an external resistance formed by two $20 \,\Omega$ resistors connected in parallel. $A$ voltmeter connected in the circuit measures $1.2 \,V$. The internal resistance of each cell is ................. $\Omega$.

Two cells are connected between points $A$ and $B$ as shown. Cell $1$ has an emf of $12 \, V$ and an internal resistance of $3 \, \Omega$. Cell $2$ has an emf of $6 \, V$ and an internal resistance of $6 \, \Omega$. An external resistor $R$ of $4 \, \Omega$ is connected across $A$ and $B$. The current flowing through $R$ will be $............. \, A$.

In the following circuit, the current through $6 \Omega$ resistor is

Two sources of equal $emf$ are connected to an external resistance $R$. The internal resistances of the two sources are $R_1$ and $R_2$ $(R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$ is zero,then:

When two identical cells are connected either in series or in parallel across a $2 \ \Omega$ resistor,they send the same current through it. The internal resistance of each cell is: (in $\Omega$)