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PHYSICS • ELECTRICITY

Ohm’s Law

Treat voltage, resistance and current as measurable circuit quantities: animate charge flow, compare two resistors, inspect power and solve for a target current on the I–V curve.

● LIVE DC CIRCUIT1.200 A • 14.40 W
Current1.200 A
Power14.40 W
Conductance0.100 S
Reference current0.600 A
Target error0.000 A
Charge per second1.200 C/s

I–V characteristic

slope = conductance

Use the resistor as a transfer function

The I–V graph makes proportionality visible: each resistor is a straight line through the origin, and its slope is conductance 1/R. The moving charge markers show current magnitude without pretending individual electron drift speed equals circuit propagation speed.

Fast investigations

  1. Double voltage at fixed resistance and verify current and power response.
  2. Double resistance at fixed voltage and compare the I–V slope.
  3. Match a target current using different V/R combinations.
  4. Compare 10 Ω and 20 Ω at the same voltage and inspect conductance.

LEARN WITH THE SIMULATION

Understand Ohm’s Law by experimenting.

START HERE

Ohm’s law links voltage, current and resistance for an ideal ohmic element. The same values also determine electrical power, which helps connect circuit behavior to energy transfer.

BUILD THE IDEA

What you should understand first

  • Use V = IR to predict current.
  • See how resistance limits current for a fixed voltage.
  • Connect current and voltage to electrical power.

TRY IT YOURSELF

If resistance doubles while voltage stays fixed, what happens to current and power?

  1. Record current and power at the default resistance.
  2. Double resistance without changing voltage.
  3. Compare the ratios for current and power.
Read the visual:

Current halves, and power V²/R also halves when voltage is fixed.

WHY IT WORKS 01

Use V = IR to predict current.

Ohm’s law describes a proportional relationship for an ideal resistor held at constant conditions: V = IR. Resistance is the proportionality factor connecting electrical potential difference to current. If resistance stays fixed, doubling voltage doubles current; if voltage stays fixed, doubling resistance halves current. The straight-line behavior is therefore a model property, not a universal rule for every electrical component.

WHY IT WORKS 02

See how resistance limits current for a fixed voltage.

Electrical power links the circuit relation to energy transfer. Starting from P = VI and substituting V = IR gives P = I²R, while substituting I = V/R gives P = V²/R. These equivalent forms explain why the effect of changing resistance depends on what the source holds fixed: constant voltage and constant current lead to opposite power trends.

DO NOT MIX THESE UP

Common misconception

Ohm’s law describes ideal ohmic behavior; many real components are nonlinear. Current is not 'used up' by a resistor. Voltage is a potential difference, not a flow.

PRACTICE CHALLENGE

If resistance doubles while voltage stays fixed, what happens to current and power?

  • Record current and power at the default resistance.
  • Double resistance without changing voltage.
  • Compare the ratios for current and power.
Reveal the reasoning

Current halves, and power V²/R also halves when voltage is fixed. Ohm’s law describes ideal ohmic behavior; many real components are nonlinear. Current is not 'used up' by a resistor. Voltage is a potential difference, not a flow.

MODEL BOUNDARIES

What this simulation assumes

Every simulation simplifies reality or a mathematical system. These are the assumptions and limits to keep in mind while interpreting the results.

Model assumptions

  • The resistor is ideal and obeys a constant linear resistance.
  • The voltage source and connecting wires are ideal.
  • Temperature is assumed not to change the resistance during the experiment.

Model limitations

  • Non-ohmic devices and temperature-dependent resistance are not modeled.
  • Internal resistance, wire resistance and transient inductive or capacitive effects are omitted.

CONNECT IT

Where this matters

  • Resistor sizing
  • Battery-powered electronics
  • Electrical safety calculations

WORDS THAT MATTER

Key vocabulary

Voltage
Electric potential difference.
Current
Rate of electric charge flow.
Resistance
Opposition to current in an ohmic model.