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Difficulty: MediumHeat Transfer: Conduction

A mechanic places one end of a solid copper rod and one end of a solid steel rod into a hot forge. Both rods have the exact same length and cross-sectional area. After a few minutes, the opposite end of the copper rod becomes too hot to hold, while the opposite end of the steel rod remains relatively cool. Which of the following best explains why the heat traveled faster through the copper rod?

  1. Copper has a higher thermal conductivity, allowing heat energy to transfer more rapidly from atom to atom through the solid material.Answer
  2. B
    Heat travels through the solid copper rod via internal convection currents, which move much faster than conduction.
  3. C
    The copper rod undergoes greater thermal expansion, which physically pushes the absorbed heat energy toward the cooler end.
  4. D
    Steel possesses a specific heat capacity that traps the thermal energy at the hot end, preventing it from moving.

Answer

Copper has a higher thermal conductivity, allowing heat energy to transfer more rapidly from atom to atom through the solid material.
Conduction is the transfer of heat through a solid material by the vibration and collision of atoms and free electrons. Thermal conductivity measures how well a material facilitates this process. Because copper has a significantly higher thermal conductivity than steel, heat travels through it much faster, causing the unheated end to become hot more quickly.

Step-by-Step Solution

1
Identify the mode of heat transfer occurring in the solid metal rods.
The heat is moving through a solid material, which means the process is conduction.
Conduction is the primary method of heat transfer within solid objects.
2
Determine which property governs the rate of this heat transfer.
The rate of conduction is determined by a material's thermal conductivity.
Different materials allow heat to pass through them at different rates depending on their molecular structure.
3
Compare the properties of copper and steel based on the scenario outcome.
Because the copper rod heated up faster at the opposite end, it must have a higher thermal conductivity than steel.
High thermal conductivity means heat energy is passed rapidly from atom to atom along the length of the material.

Key Concept

Conduction and Thermal Conductivity
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Topics

Heat Transfer: Conduction

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