In the circuit shown,the current through $R_2$ is zero. If $R_4 = 2\,\Omega$ and $R_3 = 4\,\Omega$,the current through $R_3$ will be ................. $A$.

$A$ cell of emf $90\,V$ is connected across a series combination of two resistors,each of $100\,\Omega$ resistance. $A$ voltmeter of resistance $400\,\Omega$ is used to measure the potential difference across one of the resistors. The reading of the voltmeter will be $.........\,V$.

In the given circuit,calculate the value of current in the $4.5\,\Omega$ resistor in $A$.

$A$ wire of uniform resistance $\lambda \ \Omega/m$ is bent into a circle of radius $r$. Two radial wires, each of length $r$, are connected from the center $O$ to points $A$ and $B$ on the circumference, where the angle $\angle AOB = 90^\circ$. The equivalent resistance between points $A$ and $B$ is . . . . . . $\Omega$.

In the circuit shown,the reading of the ammeter (ideal) is the same with both switches open as with both closed. Find the value of resistance $R$ in $\Omega$.

If each resistor in the given figure is $9\, \Omega$,then the reading of the ammeter is .............. $A$.