In the given circuit,if the current through the $10 \Omega$ resistor is $2.5 \text{ A}$,the value of $R$ is . . . . . . . (in $Omega$)

Find the current flowing through the resistance $R_2$ of the circuit shown in the figure,if the resistances are $R_1 = 20 \ \Omega, R_2 = 30 \ \Omega$ and $R_3 = 60 \ \Omega$,and the potentials of points $1, 2$ and $3$ are $V_1 = 20 \ V, V_2 = 30 \ V$ and $V_3 = 60 \ V$ respectively. (in $A$)

Under what condition can the current passing through the 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.

When subjected to a voltage of $10 \, V$, the current through a resistor at a temperature of $40^{\circ} C$ is $0.1 \, A$. The temperature coefficient of resistance of the material of the resistor is $2 \times 10^{-4} {}^{\circ} C^{-1}$. The temperature of the resistor in ${}^{\circ} C$ when the current drops to $0.098 \, A$ is

$A$ network of four resistances is connected to a $9\,V$ battery,as shown in the figure. The magnitude of the voltage difference between the points $A$ and $B$ is .......... $V.$

In an experiment on a circuit as shown in the figure, the voltmeter shows $8 \,V$ reading. The resistance of the voltmeter is,