An electric kettle has two heating coils. When the first coil is switched on, the tea boils in $6$ minutes. When the second coil is switched on, it boils in $8$ minutes. If both coils are connected in series and switched on, how long will it take for the tea to boil?

$A$ 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 $V$)

$B_{1}$, $B_{2}$ and $B_{3}$ are three identical bulbs connected to a battery of steady $EMF$ with key $K$ closed. What happens to the brightness of the bulbs $B_{1}$ and $B_{2}$ when the key $K$ is opened?

Each element in the finite chain of resistors shown in the figure is $1\,\Omega $. $A$ current of $1\, A$ flows through the final element. Then what is the potential difference $V$ across input terminals of the chain (in $,V$)?

An electric bulb rated for $500\, W$ at $100\, V$ is used in a circuit having a $200\, V$ supply. The resistance $R$ that must be put in series with the bulb,so that the bulb draws $500\, W$,is ................. $\Omega$.

The figure shows a circuit having eight resistances of $1 \Omega$ each,labelled $R_1$ to $R_8$,and two ideal batteries with voltages $\varepsilon_1=12 V$ and $\varepsilon_2=6 V$. Which of the following statement$(s)$ is(are) correct?
$(A)$ The magnitude of current flowing through $R_1$ is $7.2 A$.
$(B)$ The magnitude of current flowing through $R_2$ is $1.2 A$.
$(C)$ The magnitude of current flowing through $R_3$ is $4.8 A$.
$(D)$ The magnitude of current flowing through $R_5$ is $2.4 A$.