ENSC1004 - Lecture 17

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ENSC1004 - Lecture 16
Thermal Properties 2 - Slides

Thermal Conductivity

• Thermal conductivity is a material’s ability to conduct heat
  $q=-k\frac{dT}{dx}$
  $q$ $-$ heat flux $J/(m^2\cdot s)$
  $k$ $-$ thermal conductivity $W/(m\cdot K)$
  $\frac{dT}{dx}$ $-$ temperature gradient $K/m$
• For a steady state heat conduction:
  $Q=qAt=-kAt\frac{\Delta T}{l}$
  $Q$ $-$ total heat transported through conductor $(J)$
  $A$ $-$ cross-sectional area $(m^2)$

Thermal Expansion

• Most solid materials expand when heated and contract when cooled
  • There are some exceptions

• If the E-r curve is asymmetric, thus increasing temperature:
  1. Increases atomic vibration amplitude
  2. Increases mean interatomic separation
  3. Results in thermal expansion
• If the E-r curve were symmetric, then increasing temperature:
  1. Increases atomic vibration amplitude
  2. Does not change interatomic separation
  3. Does not result in thermal expansion

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ENSC1004 - Lecture 18