$A$ cell has an emf of $2 \, V$ and an internal resistance of $0.1 \, \Omega$. It is connected to an external resistance of $3.9 \, \Omega$. The terminal voltage across the cell will be: (in $V$)

By a cell,a current of $0.9\, A$ flows through a $2\, \Omega$ resistor and $0.3\, A$ flows through a $7\, \Omega$ resistor. The internal resistance of the cell is ............ $\Omega$.

Two sources of equal $emf$ $E$ are connected in series 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:

Under what conditions can the current passing through a resistance $R$ be increased by short-circuiting the battery of emf $E_2$? The internal resistances of the two batteries are $r_1$ and $r_2$ respectively.

The current in the following circuit is ........... $A$.

$A$ copper wire of radius $0.1 \text{ mm}$ and resistance $2 \text{ k}\Omega$ is connected across a power supply of $40 \text{ V}$. The number of electrons transferred per second between the supply and the wire at one end is