Home › Experiments › Physics Experiments › Verification of Ohm's Law Using Virtual Simulation

Verification of Ohm's Law Using Virtual Simulation

Verification of Ohm's Law (V = IR) using a virtual circuit simulation.

Physics Experiments 20 September, 2026 10 min read
Physics Simplified
Virtual Lab Experiments

Verification of Ohm's Law Using Virtual Simulation

Experiment Type: Virtual / Online Lab Subject: Physics (Current Electricity) Level: Class 10–12

Aim

To verify Ohm's Law (V = IR) using a virtual circuit simulation and to plot the voltage–current (V-I) characteristics of different resistors, demonstrating that current is directly proportional to voltage for an ohmic conductor.

Software / Tools Required

Virtual Circuit Simulator

Any one of the following: PhET Ohm's Law Simulator (University of Colorado), Tinkercad Circuits (by Autodesk), or Falstad Circuit Simulator. All are free and browser-based.

Web Browser

A modern web browser such as Google Chrome, Mozilla Firefox, or Microsoft Edge with JavaScript enabled.

Spreadsheet Software

Microsoft Excel, Google Sheets, or LibreOffice Calc for recording observations and plotting V-I characteristic graphs.

Theory & Principle

Ohm's Law, formulated by Georg Simon Ohm in 1827, states that the electric current flowing through a conductor is directly proportional to the potential difference (voltage) applied across its ends, provided the physical conditions such as temperature remain constant. This fundamental relationship is expressed mathematically as:

V = I × R
where V = Voltage (volts), I = Current (amperes), R = Resistance (ohms)

For a metallic conductor maintained at a constant temperature, the ratio of voltage to current remains constant and equals the resistance of the conductor. This means that if you double the voltage across a fixed resistor, the current through it also doubles.

Key Insight: The V-I graph for an ohmic conductor is a straight line passing through the origin. The slope of this line gives the resistance: R = V / I = slope of the V-I graph. A steeper line indicates a higher resistance.

Rearranging Ohm's Law provides two additional useful forms:

I = V / R     and     R = V / I
Current from voltage and resistance; Resistance from voltage and current

Why Use Virtual Simulation?

Virtual circuit simulations provide several advantages over physical experiments for verifying Ohm's Law:

  • Ideal Components: Simulated resistors have exact values with zero tolerance, eliminating manufacturing variability.
  • Instant Measurement: Digital readouts provide precise voltage and current values without parallax or resolution errors.
  • Multiple Resistors: You can instantly swap resistor values to compare V-I characteristics without rewiring the circuit.
  • No Heating Effects: Virtual components do not experience Joule heating, so resistance remains truly constant across all voltage levels.
Ohmic vs Non-Ohmic: Conductors that obey Ohm's Law (metals, most resistors) are called ohmic conductors. Components like diodes, LEDs, and filament bulbs do not obey Ohm's Law — their resistance changes with current — and are called non-ohmic conductors.

Virtual Setup Diagram

The following diagram represents the virtual circuit as it appears on the simulation screen. The circuit consists of an adjustable battery, an ammeter in series, a resistor, and a voltmeter in parallel with the resistor.

Ohm's Law Virtual Circuit Simulator Battery + - V Voltage Slider A 0.050 A Ammeter R = 100 Ω Resistor V 5.00 V Voltmeter READINGS V = 5.00 V I = 50.0 mA

Figure 1: Virtual circuit simulation setup — adjustable battery, ammeter (series), resistor, and voltmeter (parallel). Digital readouts display precise values.

Procedure

  1. Open the virtual simulator: Launch the PhET Ohm's Law Simulator (or Tinkercad Circuits / Falstad) in your web browser. If using PhET, navigate to phet.colorado.edu and search for "Ohm's Law" or "Circuit Construction Kit."
  2. Build the circuit: Place a battery (voltage source), a resistor, and connecting wires to form a simple series circuit. Insert an ammeter in series with the resistor to measure current. Connect a voltmeter in parallel across the resistor to measure the potential difference.
  3. Set the first resistance value: Set the resistor value to R = 100 Ω. In PhET, use the resistance slider; in Tinkercad, select the resistor and type the value in the component inspector.
  4. Vary the voltage systematically: Starting from 0 V, increase the battery voltage in steps of 1 V up to 10 V. At each step, allow the simulation to stabilize (readings update instantly in most simulators).
  5. Record voltage and current: For each voltage setting, note down the voltmeter reading (V) and ammeter reading (I) in the observation table. Since the simulation uses ideal components, these readings will follow V = IR exactly.
  6. Repeat for R = 220 Ω: Change the resistor value to 220 Ω without altering the rest of the circuit. Repeat the voltage variation from 2 V to 10 V in 2 V steps, recording V and I at each step.
  7. Repeat for R = 470 Ω: Change the resistor value to 470 Ω. Again vary the voltage from 2 V to 10 V in 2 V steps and record the observations.
  8. Plot V-I graphs: Using a spreadsheet or graph paper, plot voltage (V) on the y-axis and current (I) on the x-axis for all three resistors on the same graph. Draw the best-fit straight line through each set of data points.
Simulation Advantage: Unlike real experiments where contact resistance, wire resistance, and meter loading affect readings, virtual simulations provide perfectly ideal results. This makes it easier to verify the theoretical relationship V = IR without experimental noise. Use this as a benchmark to understand what deviation-free data looks like before performing the physical experiment.

Observation Table

Table 1: Resistance R = 100 Ω

S. No. Voltage, V (volts) Current, I (mA) V / I (Ω)
12.020.00100
24.040.00100
36.060.00100
48.080.00100
510.0100.00100

Table 2: Resistance R = 220 Ω

S. No. Voltage, V (volts) Current, I (mA) V / I (Ω)
12.09.09220
24.018.18220
36.027.27220
48.036.36220
510.045.45220

Table 3: Resistance R = 470 Ω

S. No. Voltage, V (volts) Current, I (mA) V / I (Ω)
12.04.26470
24.08.51470
36.012.77470
48.017.02470
510.021.28470
Note: Since the virtual simulation uses ideal components with no tolerance, internal resistance, or thermal effects, the ratio V/I yields exactly the set resistance value for every reading. In a physical experiment, slight variations (typically 1–5%) would be observed due to real-world factors.

V-I Characteristic Graph

The following graph plots voltage (V) on the y-axis against current (I) on the x-axis for all three resistance values. Each straight line through the origin confirms that V is directly proportional to I, verifying Ohm's Law.

V-I Characteristics: Verification of Ohm's Law 0 20 40 60 80 100 Current, I (mA) → 0 2 4 6 8 10 Voltage, V (volts) → Legend R = 100 Ω R = 220 Ω R = 470 Ω All three lines pass through the origin, confirming V ∝ I (Ohm's Law verified)

Figure 2: V-I characteristics for R = 100 Ω, 220 Ω, and 470 Ω. Steeper slopes indicate higher resistance. All lines are perfectly straight and pass through the origin.

Calculations

The resistance of each resistor is calculated from the slope of its V-I graph. Since the graph plots V on the y-axis and I on the x-axis, the slope equals the resistance:

R = Slope = ΔV / ΔI
Resistance equals the slope of the V vs. I graph
Calculation for R = 100 Ω
Taking two points from the observation table: (I₁ = 20 mA, V₁ = 2 V) and (I₂ = 100 mA, V₂ = 10 V)
R = ΔV / ΔI = (10 - 2) / (100 - 20) × 10³ = 8 / 0.080 = 100 Ω
Set value = 100 Ω. Deviation = 0%.
Calculation for R = 220 Ω
Taking two points: (I₁ = 9.09 mA, V₁ = 2 V) and (I₂ = 45.45 mA, V₂ = 10 V)
R = ΔV / ΔI = (10 - 2) / (45.45 - 9.09) × 10³ = 8 / 0.03636 = 220 Ω
Set value = 220 Ω. Deviation = 0%.
Calculation for R = 470 Ω
Taking two points: (I₁ = 4.26 mA, V₁ = 2 V) and (I₂ = 21.28 mA, V₂ = 10 V)
R = ΔV / ΔI = (10 - 2) / (21.28 - 4.26) × 10³ = 8 / 0.01702 = 470 Ω
Set value = 470 Ω. Deviation = 0%.
Conclusion from Calculations: For all three resistors, the resistance calculated from the slope of the V-I graph matches the set value exactly, with 0% deviation. This is expected in a virtual simulation where ideal components are used.

Result

Ohm's Law is verified. The V-I characteristic graphs for all three resistors (100 Ω, 220 Ω, and 470 Ω) are perfectly linear straight lines passing through the origin, confirming that voltage is directly proportional to current for an ohmic conductor. The calculated resistance from the slope of each graph matches the input resistance value exactly with 0% deviation, as expected in a virtual simulation with ideal components.

The experiment demonstrates that:

  • The relationship V = IR holds true for all tested resistor values.
  • The V-I graph is a straight line through the origin, confirming direct proportionality.
  • Higher resistance produces a steeper V-I line (greater slope), meaning less current flows for the same applied voltage.
  • The ratio V/I remains constant for a given resistor across all voltage levels, verifying the constancy of resistance.

Advantages of Virtual Lab

Performing this experiment in a virtual environment offers several practical benefits over a traditional physical laboratory setup:

⚡

No Equipment Damage

Virtual components cannot burn out, short-circuit, or be damaged by incorrect connections. Students can experiment freely without risk to expensive lab equipment.

????

Exact Results

Simulated instruments provide perfectly precise readings without parallax errors, calibration drift, or contact resistance, making it ideal for understanding the theoretical relationship.

????

Easy Repetition

Changing resistor values, voltage ranges, and circuit configurations takes seconds. Multiple trials can be completed in a fraction of the time needed for a physical setup.

????

Complete Safety

No risk of electric shock, overheating, or fire hazards. Students at all levels can safely explore circuit behavior, including extreme voltage and current values.

????

Accessible Anywhere

Requires only a web browser and internet connection. Students can perform the experiment from home, library, or classroom without needing a physical laboratory.

Viva Voce Questions

Q1: Why is the V-I graph a straight line for an ohmic conductor?

The V-I graph is a straight line because, according to Ohm's Law, the current through a metallic conductor is directly proportional to the voltage applied across it, provided the temperature and other physical conditions remain constant. The constant of proportionality is the resistance (R), which remains fixed, making the relationship linear: V = IR. Mathematically, this is the equation of a straight line passing through the origin with slope equal to R.

Q2: How would non-ohmic conductors behave in a virtual simulation?

Non-ohmic conductors such as diodes, filament lamps, and thermistors would produce curved V-I graphs even in a virtual simulation, because the simulator models their non-linear behaviour. For a diode, the graph shows negligible current in reverse bias and below the threshold voltage, then a sharp exponential rise once the threshold (about 0.7 V for silicon) is exceeded. A filament lamp shows a curve because the simulator accounts for the temperature-dependent resistance: as current increases, the filament heats up, increasing its resistance, so the graph bends away from a straight line. A thermistor (NTC type) shows decreasing resistance with increasing temperature.

Q3: What causes deviation from Ohm's Law in real experiments?

In real experiments, several factors cause deviation from the ideal Ohm's Law relationship:

  • Joule heating: Current flowing through the resistor generates heat, which increases the temperature and hence the resistance of the conductor.
  • Contact resistance: Loose or oxidised connections at terminals introduce additional, variable resistance.
  • Internal resistance of the battery: The battery itself has resistance, so the terminal voltage drops as current increases.
  • Instrument limitations: Ammeter and voltmeter have finite resolution and accuracy, introducing measurement errors and parallax.
  • Supply fluctuations: Power supply voltage may not remain perfectly stable during readings.
Q4: What is the difference between resistance and resistivity?

Resistance (R) is the opposition to current flow offered by a specific conductor. It depends on the material, length, cross-sectional area, and temperature of the conductor. It is measured in ohms (Ω) and is an extrinsic property — different pieces of the same material can have different resistance values.

Resistivity (ρ) is an intrinsic property of the material itself, independent of the conductor's dimensions. It represents the resistance offered by a unit cube of the material. The relationship between them is:

R = ρ × L / A

where L is the length and A is the cross-sectional area. Resistivity is measured in ohm-metres (Ω·m). For example, copper has a low resistivity (~1.7 × 10⁻⁸ Ω·m), while glass has a very high resistivity (~10¹⁰ Ω·m).

Q5: Name three applications of Ohm's Law in daily life.

Ohm's Law is fundamental to almost all electrical and electronic systems. Three common applications are:

  1. Circuit design: Engineers use V = IR to calculate the correct resistor values for LED circuits, voltage dividers, and power supplies. For example, selecting the right current-limiting resistor for an LED prevents it from burning out.
  2. Electrical safety (fuse selection): Fuse ratings are determined using Ohm's Law. By knowing the supply voltage and the maximum safe current for a circuit, the appropriate fuse value is calculated to protect against overcurrent.
  3. Household appliances: The power rating and current draw of heaters, toasters, electric irons, and hair dryers are designed using Ohm's Law combined with the power equation P = VI. This determines the gauge of wiring needed and the circuit breaker rating.

Related Experiments

Continue exploring circuit theory with the following experiment:

← Wheatstone Bridge & Kirchhoff's Law Derivation