Chapter 5 L11 Flashcards
Give 2 definitions for Heat Capacity
- Capacity of a material to abosotb heat from the surroundings
- Amount of energy needed to increase 1 temperature unit
What is thermal expansion?
Increase in volume due to temperature increase
How is thermal expansion related to temperature? How does the process take place?
An increase in temperature causes particules to vibrate. When certain energy level is reached, particules start to move away from each other and expand
How can thermal expansion be used for mechanical assemblies?
Shrink and expansion fits
What is heat conductivity? How can it be transfered
Transmission of heat due to lattice vibrations or free electrons
CTE
Coefficent of thermal expansion
What is a phonon?
Vibration of the lattice
State the Wiedemann-Franz Law
- Electric and heat transfer involve free electrons
- Formula in “Notes”
What is a thermal shock?
Fracture as a consquence of non-uniformal dimensional changes
Name the most important heat property of metals and ceramics
- Metals: Heat transport through electrons is more efficient
- Cermics: Thermal expansion is low (Shock)
What is the Fermi energy?
It is the highest energy level that electrons ocuppy in a solid at 0k
What is a superconductor?
A conductor that conducts electricity with no resitance below certain temperature
What factors influence electric resistance?
- Tempertaure
- Impurities
- Lattice related
Difference between semiconductor and insulators
Width of the band gap “Notes”
Difference between intrinsic and extrinsic insulators
- Intrinsic: Electrical beheaviour based purely on material properties (1 atom)
- Extrinsic: Electrical characteristics based on impurity atoms (n and p) (more than 1 atom)
- “Notes”
Causes of degradation of polymers?
- Thermal oxidation:
Oxygen introduction in the polymer structure - UV radiation:
Short wavelenghts break molecular bonds - Hydrolysis:
Contact with water alter mechanical properties
(swelling)
