MP Board · Class 10 · Science · ElectricityState Ohm's Law. Describe an activity with a well-labeled circuit diagram to verify Ohm's law experimentally. Also, explain the factors on which the resistance of a conductor depends.

Statement of Ohm's Law\nOhm's law states that the electric potential difference (V) across a metallic wire in a circuit is directly proportional to the electric current (I) flowing through it, provided its temperature remains constant.\nMathematically:

[V \propto I \implies V = IR]\nwhere (R) is a constant called resistance.

Experimental Verification of Ohm's Law

1. Apparatus Required: A resistance wire ((R)), an ammeter ((A)), a voltmeter ((V)), a battery ((B)), a plug key ((K)), and a rheostat ((Rh)).
2. Circuit Diagram Setup: Connect the components in series forming a closed loop with the battery, key, ammeter, and resistance wire. Connect the voltmeter in parallel across the resistance wire.
3. Procedure:
   • Close the key ((K)) to allow current to flow through the circuit.
   • Note the reading of current ((I)) from the ammeter and potential difference ((V)) from the voltmeter.
   • Change the current in the circuit by using the rheostat and record the corresponding readings of (V) and (I).
   • Calculate the ratio (V/I) for each set of readings.
4. Observation and Conclusion: It is observed that the ratio (V/I) remains constant every time. When a graph is plotted between (V) and (I), a straight line passing through the origin is obtained, which verifies Ohm's law.

Factors Affecting Resistance of a Conductor\nThe resistance (R) of a uniform metallic conductor depends on:

• Length ((l)): Resistance is directly proportional to the length of the conductor ((R \propto l)).
• Area of Cross-section ((A)): Resistance is inversely proportional to the cross-sectional area ((R \propto 1/A)).
• Nature of Material: Different materials have different free electron densities, leading to varying resistances.
• Temperature: Resistance of metallic conductors increases with an increase in temperature.