How Ohm’s Law Can Be Verified Experimentally
Ohm’s law states that the current flowing through a conductor is directly proportional to the voltage across it, provided that temperature and other physical conditions remain constant.
An Ohm’s law experiment can be used to verify this relationship by measuring the voltage across a resistor and the current flowing through it.
What You Need for the Experiment
The typical setup requires:
A DC power supply or battery
A resistor
An ammeter
A voltmeter
A variable resistor (rheostat)
Connecting wires
A switch
The ammeter is connected in series with the resistor, while the voltmeter is connected in parallel across the resistor.
Procedure for Verifying Ohm’s Law
Connect the circuit with the ammeter in series and the voltmeter across the resistor.
Set the variable resistor to provide a relatively low current.
Switch on the circuit and record the voltage and current readings.
Adjust the variable resistor to change the current.
Record several pairs of voltage and current readings.
Calculate the resistance for each reading using the measured voltage and current.
Plot a graph of voltage against current.
How the Results Verify Ohm’s Law
If the experiment follows Ohm’s law, increasing the voltage should produce a proportional increase in current.
For example, if the voltage is doubled while the resistance remains constant, the current should also approximately double.
A graph of voltage (V) against current (I) should produce a straight line passing close to the origin. The slope of this graph represents the resistance of the conductor.
If the calculated resistance remains approximately constant for the different measurements, this provides experimental evidence that Ohm’s law is being followed.
Example Observation Table
| Voltage (V) | Current (A) | V/I (Ω) |
|---|---|---|
| 2 | 0.20 | 10 |
| 4 | 0.40 | 10 |
| 6 | 0.60 | 10 |
| 8 | 0.80 | 10 |
The value of V/I remains approximately constant in this example, indicating that the resistance is about 10 Ω.
Precautions
For a reliable Ohm’s law experiment:
Keep the temperature of the resistor as constant as possible.
Avoid allowing excessive current to flow through the resistor.
Check that the ammeter and voltmeter are connected correctly.
Take several readings rather than relying on a single measurement.
Make sure the electrical connections are secure.
Switch off the circuit when measurements are not being taken.
Conclusion
Ohm’s law can be verified experimentally by measuring different values of voltage and current for a conductor while keeping its physical conditions, particularly temperature, reasonably constant. If the ratio V/I remains approximately constant and the voltage-current graph is approximately a straight line through the origin, the experimental results support Ohm’s law.
For quick calculations involving voltage, current, and resistance, an Ohm’s Law Calculator can also be used to determine the missing electrical value.