$A$ $50\, W$ bulb is in series with a room heater and the combination is connected across the mains. To get maximum heater output,the $50\, W$ bulb should be replaced by a bulb of: (in $, W$)

Current flowing through the cell and potential difference between its two poles obtained by observations are given in the table below. The internal resistance of the cell is $r$.

Order	$V \ (V)$	$I \ (A)$
$1$	$1.0$	$0.08$
$2$	$0.5$	$0.18$
$3$	$0.8$	$0.12$

Find the $emf$ $(\varepsilon)$ of the cell used in the experiment. (in $V$)

Inside a superconducting ring,six identical resistors each of resistance $R$ are connected as shown in the figure. The equivalent resistance$(s)$:

The storage battery of a car has an $emf$ of $12\; V$. If the internal resistance of the battery is $0.4\; \Omega,$ what is the maximum current (in $A$) that can be drawn from the battery?

If the readings of the ammeter and voltmeter are $2 \, A$ and $120 \, V$ respectively,what is the resistance of the voltmeter in $\Omega$?

When a current of $4 \, A$ is passed through a cell for $2 \, minutes$,the mass deposited at the cathode is $m \, g$. If a current of $6 \, A$ is passed through the same cell for $40 \, seconds$,what mass will be deposited at the cathode?