Question

Define Ohm’s Law and describe an experiment to verify it.

Hint:

To verify Ohm’s Law: * Keep temperature constant, * Take multiple readings of voltage and current, * A straight-line ( V\text{-}I ) graph through origin confirms Ohmic behavior.

Answer 1

Concept: Ohm’s Law is a fundamental principle in electricity that relates current, voltage, and resistance in an electrical conductor. It states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided the temperature and other physical conditions remain constant. Mathematically, [ V \propto I \quad \Rightarrow \quad V = IR ] where:

• ( V ) = Potential difference (Volts)
• ( I ) = Current (Amperes)
• ( R ) = Resistance (Ohms)

Thus, the ratio \[ \frac{V}{I} = R \] remains constant and is equal to the resistance of the conductor. Experimental Verification of Ohm’s Law: Apparatus Required:

• Battery or DC power supply
• Rheostat (variable resistor)
• Ammeter
• Voltmeter
• Resistance wire (nichrome wire)
• Plug key and connecting wires

Circuit Diagram: The ammeter is connected in series with the resistor and battery, while the voltmeter is connected in parallel across the resistor. Procedure:

• Connect the circuit as described: battery, rheostat, ammeter, and resistor in series.
• Connect the voltmeter in parallel across the resistor.
• Close the key and adjust the rheostat to allow a small current to flow.
• Note the readings of the ammeter (current) and voltmeter (voltage).
• Change the rheostat setting to vary the current and record multiple sets of ( V ) and ( I ) readings.
• Tabulate the observations.

Observation and Result: For each set of readings, calculate the ratio ( \frac{V}{I} ). It is found that the ratio remains nearly constant for all observations. Alternatively, plotting a graph between voltage (V) and current (I) gives a straight line passing through the origin. This confirms: [ V \propto I ] Hence, Ohm’s Law is verified experimentally. Conclusion: The experiment shows that the current through a conductor is directly proportional to the potential difference across it when temperature remains constant. The slope of the ( V\text{-}I ) graph gives the resistance of the conductor.