MATERIALS SCIENCE EXAM 3
COMPREHENSIVE STUDY GUIDE 2026
◉ Resistivity.
Answer: A = Cross sectional area of current flow
L current flow path lenghth
◉ Conductivity.
Answer: The ability of an object to transfer heat or electricity to
another object.
1/resistivity
◉ Electron energy band structures.
Answer:
◉ Conduction and electron transport (Metals).
Answer: - For metals, empty energy states are adjacent to filled
states
- Thermal energy excites electrons into empty higher energy states
- Two types of band structures for metals (partially filled band,
empty band that overlaps filled band)
,◉ Insulators.
Answer: materials that prevent electric charges from flowing
through them easily
-wide band gap (>2ev)
- few electrons excited across the band gap
◉ Semiconductors.
Answer: -Narrow band gap
-Electrons with enough energy are excited across the band gap
-low temperature, low electron energy
-High temperature, high electron energy
◉ Influence of temp on resistivity.
Answer: resistivity increases with temp
◉ influence of impurities on resistivity.
Answer: imperfections increase resistivity
- Grain boundaries, dislocations, etc., act to scatter electrons so they
take a less direct path.
◉ two types of charge carriers in insulators and semiconductors.
, Answer: Free electron: negative charge and is in the conduction
band
Hole: positive charge and a vacant electron state in the valence band
◉ Intrinsic semiconductors.
Answer: Pure Metals (alloys); no impurities
◉ Compound Semiconductors.
Answer: A semiconducting material formed from two or more
elements.
- The wider the electronegativity difference between the two
materials the wider the band gap.
◉ Electron & Hole Migration.
Answer:
◉ Electrical conductivity equation.
Answer: n = electrons/m^3
mew sube = electron mobility
mew sub h = hole mobility
COMPREHENSIVE STUDY GUIDE 2026
◉ Resistivity.
Answer: A = Cross sectional area of current flow
L current flow path lenghth
◉ Conductivity.
Answer: The ability of an object to transfer heat or electricity to
another object.
1/resistivity
◉ Electron energy band structures.
Answer:
◉ Conduction and electron transport (Metals).
Answer: - For metals, empty energy states are adjacent to filled
states
- Thermal energy excites electrons into empty higher energy states
- Two types of band structures for metals (partially filled band,
empty band that overlaps filled band)
,◉ Insulators.
Answer: materials that prevent electric charges from flowing
through them easily
-wide band gap (>2ev)
- few electrons excited across the band gap
◉ Semiconductors.
Answer: -Narrow band gap
-Electrons with enough energy are excited across the band gap
-low temperature, low electron energy
-High temperature, high electron energy
◉ Influence of temp on resistivity.
Answer: resistivity increases with temp
◉ influence of impurities on resistivity.
Answer: imperfections increase resistivity
- Grain boundaries, dislocations, etc., act to scatter electrons so they
take a less direct path.
◉ two types of charge carriers in insulators and semiconductors.
, Answer: Free electron: negative charge and is in the conduction
band
Hole: positive charge and a vacant electron state in the valence band
◉ Intrinsic semiconductors.
Answer: Pure Metals (alloys); no impurities
◉ Compound Semiconductors.
Answer: A semiconducting material formed from two or more
elements.
- The wider the electronegativity difference between the two
materials the wider the band gap.
◉ Electron & Hole Migration.
Answer:
◉ Electrical conductivity equation.
Answer: n = electrons/m^3
mew sube = electron mobility
mew sub h = hole mobility
