Explain the electron contribution in metal conduction
Add mobile electrons to the lattice account without requiring an electric circuit or net bulk current.
Section P2.3.1 · Conduction
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Explain lattice-vibration conduction.
- Distinguish thermal energy transfer from an imposed electric current.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which additional thermal-transfer route is important in metallic conductors?
What you will learn
- Explain the role of free delocalised electrons in metallic thermal conduction.
- Retain lattice transfer as well as the electron contribution.
Metallic conductors have an additional route
In metals, free or delocalised electrons can move through the structure. They exchange energy through interactions, contributing to transfer from hotter to cooler regions. Lattice vibrations also transfer energy. The useful explanation includes both routes rather than saying the solid lattice becomes irrelevant when mobile electrons are present.
The electrons do not need a battery or externally driven electric current for a warmed metal bar to conduct thermal energy. Thermal transport and electrical current are different descriptions; a particle diagram is not a circuit diagram. Avoid treating an arrow of energy as a claim that every electron has the same speed or one continuous uncollided path.
Compare mechanisms with conditions
A non-metallic solid can still conduct through its particle interactions even when the metallic free-electron mechanism is absent. Metals are generally good thermal conductors in the school examples, but actual material properties, dimensions and temperatures matter when making quantitative comparisons.
The diagram distinguishes fixed lattice positions from selected mobile-electron paths schematically. It does not draw electron sizes to scale or count actual electron populations. A greater transfer rate in a supplied controlled test supports the material comparison, while a measured circuit current is not required to prove that thermal energy can pass through a metal.
Sources for this lesson
Pause and explain
How should the solid metal explanation be stated?
Worked example
A metal rod conducts from a warmer end with no battery connected. Explain why that is possible.
Show the worked solution
- Lattice vibrations transfer energy.
- Mobile delocalised electrons provide an additional contribution in the metal.
- An externally imposed electrical current is not required for this thermal process.
Answer Both lattice interactions and mobile electrons can conduct thermal energy without a battery.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain the two thermal-transfer contributions in a metal bar.
Give me a hint
Describe lattice interactions and mobile electrons separately.
Compare my reasoning
- Particles vibrate about lattice positions and exchange energy.
- Delocalised electrons move and exchange energy within the metal.
- Both contribute without requiring bulk movement of the bar.
Lattice-vibration transfer and the mobile-electron contribution.
Look for these in your work
- Include both mechanisms.
- Avoid bulk material flow.
A non-metallic solid has no metallic free-electron route in the supplied model. Must its conduction be zero?
Give me a hint
The general lattice mechanism remains.
Compare my reasoning
- Its particles can vibrate and interact.
- Those interactions can transfer thermal energy.
- Lacking the additional metallic route does not establish zero conduction.
No; lattice interactions can still conduct thermal energy.
Look for these in your work
- Retain the general mechanism.
- Reject the perfect-barrier inference.
A stationary metal rod has a temperature difference but no battery. Someone claims its electrons cannot contribute. Explain the error.
Give me a hint
Do not equate thermal transport with an imposed circuit current.
Compare my reasoning
- Delocalised electrons are mobile within the material.
- They can exchange thermal energy under the stated temperature difference.
- The process does not require a battery-driven current.
Mobile electrons can contribute to thermal conduction without an external electrical supply.
Look for these in your work
- Separate thermal and electrical descriptions.
- Keep the lattice contribution as well.
Common mistakes
- Keep both lattice and electron contributions.
- Thermal conduction does not require an external circuit.
- Non-metals can also conduct through particle interactions.
What can you explain now?
Does a metal rod need a battery to conduct thermal energy?
Compare with the explanation
No.
Its mobile electrons and lattice can transfer energy under a temperature difference without an imposed circuit current.
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Make it stick
Explain metallic conduction using both lattice vibrations and mobile electrons with no compulsory circuit.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.