Thermodynamics
Conduction bar
Heat flows through the bar at Q/t = kAΔT/L.
Conduction bar — interactive Thermodynamics simulation. Heat flows through the bar at Q/t = kAΔT/L. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Heat conduction
Heat flows through the bar at Q/t = kAΔT/L.
Fourier's law of conduction sends heat faster when the temperature gradient is larger, the cross-section is bigger, or the material has higher thermal conductivity k. The bar geometry is chosen so the steady-state heat current is easy to read from end temperatures.
- Q/t = kAΔT/L
- Fourier law
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A copper bar connects a hot body and a cold body. If you use a thicker bar (more cross-sectional area), does heat flow through it faster or slower?
Predictions to weigh
- A thicker bar conducts heat faster — more area means a wider path for heat flow.
- A thicker bar conducts heat slower.
- Bar thickness doesn't affect the conduction rate.
Variable roles
What you set:
- Cross-sectional area A (m²)
What you measure:
- Heat-flow rate Q̇ (W)
How the investigation runs
- Open the conduction-bar preset and press Reset. A copper bar (k = 401 W/(m·K), length 0.1 m) connects a 450 K body to a 300 K body.
- Enable the heat-flow-rate readout on the conductor.
- Set the bar's cross-sectional area for each trial and record the heat-flow rate.
Governing equation
Fourier's Law of Conduction — Q/t = k·A·ΔT / L
Heat flows through a material at a rate set by its conductivity, cross-sectional area, temperature difference, and length: Q̇ = kAΔT/L. Bigger area or temperature difference speeds up conduction; a longer path slows it down.
What the printable worksheet asks students to work out
- For one trial, compute Q̇ = kAΔT/L using k = 401 W/(m·K), ΔT = 150 K, L = 0.1 m. Compare to the table.
- Explain, using Fourier's law, why doubling the bar's cross-sectional area doubles the rate of heat flow at fixed temperature difference and length.
Where this shows up beyond the lab
- A material with low thermal conductivity (like glass, k ≈ 0.8 W/(m·K)) conducts heat far more slowly than copper (k = 401 W/(m·K)) for the same area and length. Explain why house insulation uses low-k materials.
- This experiment varies area, but the formula also has length L in the denominator. Would doubling the bar's length double or halve the heat-flow rate? Explain why a longer path resists heat flow more.
- AP Physics 2 — Unit 9: Thermodynamics
- IB Physics — B.1 Thermal energy transfers
- General High School Physics — Heat, temperature & gas laws
- NGSS High School Physics — Thermal energy transfer
- Middle School Physical Science — Controlling heat transfer
- Middle School Physical Science — Energy transfer between materials
- Welcome to Conduction Bar
- Select the conductor
- Press Play
- Heat through the bar
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.