We already know the statement of Ohm’s Law which is
“If the physical state of the conductor (Temperature and mechanical strain etc.) remains unchanged, then current flowing through a conductor is always directly proportional to the potential difference across the two ends of the conductor”
where constant of proportionality R is called the electric resistance or simply resistance of the conductor.
Ohm’s Law can be verified is we manage to show that for a given conductor (piece of wire) the ratio V:I is constant. Resistance of the conductor is a constant for a known temperature range.
To verify this law you can set up a circuit with resistors of fixed values, a variable voltage source, a voltmeter and an ammeter as shown below in the figure
Take one resistor, connect a voltmeter parallel to it and an ammeter in series to the resistor and the voltage source. Change the voltage; take the reading from the voltmeter and the corresponding current reading from the ammeter. Plot a graph with voltages along X axis and current along Y axis. You should get a straight line of the form y = mx
Repeat the same taking different values of resistors. ‘m’ will be different for different resistances. The Ohm’s will be verified if for each values of resistances, the V-I graph is of the form y = mx. That is a straight line passing through the origin, making an angle with the axes.