If the ammeter in the given circuit reads $2\, A$,the resistance $R$ is ............ $\Omega$.

If a high power heater is connected to electric mains,then the bulbs in the house become dim,because there is a

Two batteries of e.m.f. $4\,V$ and $8\,V$ with internal resistances $1\,\Omega$ and $2\,\Omega$ 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 $Q$ are

$A$ heating coil is labelled $100\, W$,$220\, V$. The coil is cut in half and the two pieces are joined in parallel to the same source. The energy now liberated per second is .............. $J/s$.

When a resistance of $2\,\Omega$ is connected across the terminals of a cell,the current is $0.5\,A$. When the resistance is increased to $5\,\Omega$,the current is $0.25\,A$. The $e.m.f.$ of the cell is ................. $V$.

In the circuit shown, the reading of the ammeter when switch $S$ is open and when switch $S$ is closed respectively are