Ohm's Law Virtual Laboratory

Physics & Electrical Engineering Interactive Experiment

✓ EXPERIMENT VERIFIED
Experiment Mode:
Investigate how current \( I \) varies proportionally with voltage \( V \) when resistance \( R \) is kept constant.

Interactive DC Circuit Schematic

Conductors Current Flow
12.0 V DC POWER SOURCE + - AMMETER 0.60 A A R = 20 Ω + - VOLTMETER (PARALLEL) 12.00 V KNIFE SWITCH CLOSED (ON)
Applied Voltage (\(V\))
12.0 V
Power Supply Terminal
Circuit Resistance (\(R\))
20.0 Ω
Resistor Load
Measured Current (\(I\))
0.60 A
Series Ammeter Flow
Power Dissipation (\(P\))
7.20 W
\(P = V \times I = I^2 R\)

Experimental V-I Characteristic Curve

Plotting Current (\(I\)) vs. Voltage (\(V\)) at Fixed \(R = 20.0\,\Omega\)

Legend: Theoretical Curve   |   Recorded Data Points

Experimental Observation Table

0 Readings
# Voltage \(V\) (V) Resistance \(R\) (Ω) Current \(I\) (A) Power \(P\) (W) Calc \(R = V/I\)
No experimental data recorded yet. Adjust controls and click "Record Reading" to collect data.

Ohm's Law Laboratory Manual & Engineering Guide

1. About the Experiment

Ohm's Law is a foundational principle of physics and electrical engineering discovered by German physicist Georg Simon Ohm in 1827. It establishes the fundamental relationship between electric potential difference (voltage), electric current, and resistance in a linear DC circuit element.

2. Governing Working Principles

In a conductor under constant temperature and physical state, the electric current \( I \) flowing through a resistor is directly proportional to the applied potential difference \( V \) across it:

\[ V = I \times R \]
\[ I = \frac{V}{R} \qquad R = \frac{V}{I} \]

Joule's Heating & Power Dissipation: The electrical power \( P \) converted into thermal energy inside the resistor is expressed as:

\[ P = V \times I = I^2 R = \frac{V^2}{R} \quad \text{(Watts)} \]

3. Experimental Procedure

  1. Fixed Resistance Test (Mode 1): Set the resistance slider to a fixed value (e.g. \( 20\,\Omega \)). Enable the circuit switch (ON). Gradually increase the voltage from \( 0\text{ V} \) to \( 24\text{ V} \) in steps of \( 3\text{ V} \). Click "Record Reading" at each step to plot the linear \( I \) vs. \( V \) line.
  2. Fixed Voltage Test (Mode 2): Switch to Mode 2. Fix the supply voltage to \( 12\text{ V} \). Vary the load resistance from \( 5\,\Omega \) to \( 100\,\Omega \). Observe how current decreases non-linearly following a hyperbolic relationship \( I = V/R \).
  3. Data Verification: Compute \( R = V/I \) for each row in the observation table and confirm that it matches the physical resistance setting within machine precision.

4. Real-World Engineering Applications

  • Circuit Current Limiting: Selecting pull-up/pull-down resistors to protect microcontrollers and delicate LEDs from overcurrent destruction.
  • Power Rating & Thermal Management: Sizing resistors according to their power ratings (\(\frac{1}{4}\text{W}\), \(1\text{W}\), \(5\text{W}\)) to prevent thermal burnout.
  • Printed Circuit Board (PCB) Trace Widths: Ensuring copper trace dimensions provide low resistance to minimize parasitic voltage drops (\(I \cdot R\)).