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 $A$)

Water boils in an electric kettle in $15\,\text{min}$ after switching on. If the length of the heating wire is decreased to $2/3$ of its initial value,then the same amount of water will boil with the same supply voltage in ............. $\text{min}$.

The series combination of two batteries,both of the same emf $10 \; V,$ but different internal resistances of $20 \; \Omega$ and $5 \; \Omega,$ is connected to the parallel combination of two resistors $30 \; \Omega$ and $R \; \Omega.$ If the voltage difference across the battery of internal resistance $20 \; \Omega$ is zero,the value of $R$ (in $\Omega$) is:

The terminal voltage of the battery, whose emf is $10 \, V$ and internal resistance is $1 \, \Omega$, when connected through an external resistance of $4 \, \Omega$ as shown in the figure is: (in $V$)

$A$ cell whose e.m.f. is $2\, V$ and internal resistance is $0.1\,\Omega$ is connected with a resistance of $3.9\,\Omega$. The voltage across the cell terminal will be ................ $V$.

$A$ voltameter has a resistance of $2\,\Omega$. It is connected in series with a $10\,V$ battery and a $3\,\Omega$ resistor. The mass deposited at the cathode in a certain time is $1\,g$. Now,the voltameter and the $3\,\Omega$ resistor are connected in parallel with the battery. The increase in the mass of the metal deposited in the same time will be $...\,g$.