SciSimulator
Back to Experiment

Ohm's Law Virtual Lab Guide

PhysicsBeginnerReading time: 3 min

Overview

Ohm's Law is the foundation of circuit analysis, describing the quantitative relationship between current, voltage, and resistance in a conductor. Through this interactive simulation, you will personally verify the V=IRV = IR formula and explore how voltage and resistance together determine the magnitude of current.

Background

In 1826, German physicist Georg Simon Ohm discovered this fundamental quantitative relationship through extensive experimentation. Although his findings were initially neglected, they later proved to be one of the most important cornerstones of electrical science. Ohm's Law applies not only to single resistors but also serves as the starting point for analyzing complex circuit networks.

Key Concepts

Voltage (VV)

V (Volts, V)V \text{ (Volts, V)}

The 'pressure' that pushes charges to flow, provided by a power source. Higher voltage provides more driving force for charge movement. In circuit diagrams, it's typically provided by battery packs.

Resistance (RR)

R  (Ω)R \; (\Omega)

The opposition that a conductor offers to the flow of current. Resistance is determined by the conductor's material, length, and cross-sectional area, and does not change with voltage.

Current (II)

I (Amperes, A)I \text{ (Amperes, A)}

The amount of charge passing through a conductor's cross-section per unit time. The direction of current is defined as the direction of positive charge movement. In the simulation, it's represented by the flow speed of light dots.

Formulas & Derivation

Ohm's Law

I=VRI = \frac{V}{R}
Current in a conductor is directly proportional to the voltage across it and inversely proportional to its resistance. This formula only applies to linear resistors.

Derived Formulas

V=IRorR=VIV = IR \quad \text{or} \quad R = \frac{V}{I}
Given any two parameters, the third can be calculated. Note: R=V/IR = V/I is only used to calculate the resistance value; resistance itself does not change with voltage.

Experiment Steps

  1. 1

    Exploring Current-Voltage Relationship

    Keep the resistance slider at 500Ω500\Omega. Gradually increase the voltage from 1.5V1.5V to 9.0V9.0V. Observe the trend of current (II) in the data panel. You'll find: when resistance is constant, the higher the voltage, the ____ the current? (Hint: Record values at different voltages and see if they are proportional.)
  2. 2

    Exploring Current-Resistance Relationship

    Keep the voltage slider at 4.5V4.5V. Increase the resistance from 100Ω100\Omega to 2000Ω2000\Omega. Notice the moving speed of the blue dots in the circuit. You'll find: when voltage is constant, the higher the resistance, the ____ the current? (Hint: When resistance doubles, what happens to the current?)
  3. 3

    Observing Extreme Cases

    Try set voltage to maximum (9.0V9.0V) and resistance to minimum (100Ω100\Omega). Notice the 'High Current' warning. When current exceeds 25mA25mA, components in real circuits may be damaged due to rapid heat generation.
  4. 4

    Changing Flow Direction

    Toggle the 'Flow Direction' button to see the difference between 'Conventional Current' and 'Electron Flow'. Think: Why do we usually use the direction from positive to negative in circuit analysis?

Learning Outcomes

  • Accurately understand and state Ohm's Law and its physical significance
  • Proficiently use the control variables method to design and execute electrical experiments
  • Master the application of V=IRV=IR and its derived formulas in basic circuit analysis
  • Develop scientific thinking by predicting experimental data based on physical laws

Real-world Applications

  • Home Appliances: Dimmer switches or audio volume knobs adjust current by changing variable resistance.
  • Circuit Safety: Fuses are designed based on the heating effect of current, automatically blowing when current is too high (determined by V/RV/R).
  • Sensor Technology: Pressure sensors in electronic scales work by changing resistance through deformation.
  • Fast Charging: Mobile devices obtain higher current (II) and power (PP) by increasing charging voltage (VV) when resistance (RR) is limited.
  • Multimeter Measurement: Uses known internal voltage and measured current to calculate unknown resistance.

Common Misconceptions

Misconception
Resistance depends on voltage and current (R=V/IR = V/I, so R changes when V changes).
Correct
Resistance is an intrinsic property of the conductor, like a person's height; it doesn't change with how fast you run (current) or how hard you're pushed (voltage). The formula R=V/IR = V/I simply provides a way to measure resistance.
Misconception
As long as there is voltage, there must be current.
Correct
Not exactly. Just like water pressure exists even if the faucet is closed. Current requires: 1. Voltage (power source); 2. A closed circuit loop.

Further Reading

Ready to start?

Now that you understand the basics, start the interactive experiment!

Start ExperimentStart Quiz