NCERT · Class 10 · Science · ElectricityState Ohm's Law. Describe an activity to verify Ohm's Law experimentally with the help of a circuit diagram, and draw the corresponding V-I graph.

Ohm's Law Statement\nOhm's Law states that the electric current flowing through a metallic wire is directly proportional to the potential difference $V$ across its ends, provided its temperature remains constant.\nMathematically: $V \propto I$ or $V = IR$, where $R$ is the resistance of the conductor.

Experimental Verification

Apparatus Required:

• A resistance wire ($R$)
• An ammeter ($A$) to measure current
• A voltmeter ($V$) to measure potential difference
• A plug key ($K$)
• A variable resistor or rheostat ($Rh$)
• A battery or cell ($B$)

Circuit Diagram Setup:

• Connect the components in a closed circuit. The battery, rheostat, ammeter, and resistance wire are connected in series. The voltmeter is connected in parallel across the resistance wire.

Procedure:

1. Close the key $K$ so that current flows through the circuit.
2. Note down the reading of the ammeter (current $I$) and voltmeter (potential difference $V$).
3. Adjust the rheostat to change the current in the circuit and record the new readings of both the ammeter and voltmeter.
4. Repeat this process for different positions of the rheostat to obtain at least 4-5 sets of readings.
5. Calculate the ratio $V/I$ for each set of observations. It will be observed that the ratio $V/I$ is nearly constant.

V-I Graph:\nPlot a graph between the potential difference $V$ (along the x-axis) and current $I$ (along the y-axis). The graph comes out to be a straight line passing through the origin. This straight line indicates that the current is directly proportional to the potential difference, thus verifying Ohm's Law.