State Ohm's law.

Sonika is working with the circuit shown in the figure. There are two open terminals in the circuit: $X$ and $Y$. She has wires made of five different materials: $I, II, III, IV,$ and $V$. She knows that the electric bulb will glow only when wires made of conducting materials are connected across both open terminals. She records her observations in a table. After the experiment,ink spills on the paper,and she loses the information for the third row.

$S.No.$	Material at $X$	Material at $Y$	Electric Bulb ($ON$/$OFF$)
$1$	$I$	$II$	$OFF$
$2$	$I$	$IV$	$ON$
$3$	-	-	$OFF$
$4$	$III$	$V$	$ON$

Based on the remaining information in the table,which materials could be in the third row?

Two wires of the same metal have the same length, but cross-sections are in the ratio $3 : 1$. They are joined in series. The resistance of the thicker wire is $10\, \Omega$. The total resistance of the combination will be:

How many electrons constitute a total charge of $1 \ C$?

Resistance of a conductor increases with the increase in temperature.

How can we measure the current in a circuit?