State $Ohm's$ law. How can it be verified?

(N/A) Ohm's law states that the current flowing through a metallic conductor is directly proportional to the potential difference applied across its ends,provided its physical conditions (like temperature) remain constant.
Mathematically,this is expressed as:
$V \propto I$
$V = IR$
Here,$V$ is the potential difference,$I$ is the current,and $R$ is the constant of proportionality known as the resistance of the conductor.
Verification:
To verify Ohm's law,set up a circuit as shown in the figure,consisting of a nichrome wire $R$,an ammeter,a voltmeter,a battery,and a rheostat $(Rh)$.
$1$. Close the key $K$ and note the current $I$ in the ammeter and potential difference $V$ in the voltmeter for a specific position of the rheostat.
$2$. Change the position of the rheostat to vary the current in the circuit and record the corresponding values of $V$ and $I$.
$3$. Calculate the ratio $V/I$ for each set of readings. You will observe that the ratio $V/I$ is constant.
$4$. Plot a graph of $V$ (on the y-axis) against $I$ (on the x-axis). The graph will be a straight line passing through the origin,which confirms that $V$ is directly proportional to $I$,thus verifying Ohm's law.