Experiment to verify OHM's Law.

We can find the relation between the current flowing through a wire and the potential difference applied across it with the help of a dry cell, a voltmeter (range 0 - 1.5 V), an ammeter (range 0 - 1 A), a standard fixed resistance coil (1 {tex}\Omega{/tex}), rheostat (0 - 1 {tex}\Omega{/tex}), connecting wires and a plug key.

Procedure:

1. The fixed resistor (R), the ammeter (A), the dry cell (D), the plug key (K) and the rheostat (Rh) should be connected in series (end to end).
2. The voltmeter (V) should be connected in parallel across resistor R. 
3. When the key K is open, (the circuit is disconnected), check that there is no reading in the ammeter and the voltmeter.
4. Close the key and move the sliding contact of the rheostat so that there is a small reading in the ammeter and the voltmeter. Record the readings.
5. Now, increase the value of the current with the help of the rheostat. Record the ammeter and the voltmeter readings again.
6. After changing the readings a few times, record the corresponding values of current and voltage from the ammeter and the voltmeter.
7. Plot a graph between the ammeter and the voltmeter readings.

Observations:

(i) On increasing the ammeter reading, the voltmeter reading increases in the same proportion.

(ii) The voltage-current (V - I) graph is a straight line.

Conclusion:

The current flowing through the resistor is directly proportional to the potential difference applied across its ends.