26 Questions
Which type of solid has very low resistivity and high conductivity?
Metals
What is a characteristic of semiconductors in terms of resistivity or conductivity?
Low resistivity
Which type of solid has high resistivity and low conductivity?
Insulators
What are examples of elemental semiconductors as mentioned in the text?
Si, Ge
Which type of currently available semiconductor devices are based on elemental semiconductors Si or Ge?
None of the above
What are compound inorganic semiconductors examples of?
Semiconductors
What is the resistivity range for insulators?
10^11 – 10^19 W m
Which type of solid possesses very low resistivity and high conductivity?
Metals
What is the resistivity range for metals?
10^2 – 10^8 W m
Which category of semiconductors includes examples like CdS and GaAs?
Inorganic
What are Si and Ge classified as in terms of semiconductors?
Elemental semiconductors
What is the resistivity range for semiconductors?
10^5 – 10^6 W m
What characteristic distinguishes semiconductors from metals and insulators?
Intermediate resistivity
What type of semiconductor devices are most currently available ones based on?
$Si$ and $Ge$
Which type of solids could have values of r and s that go outside their indicative ranges?
All three types: Metals, insulators, and semiconductors
What is the unit for conductivity?
$S m^{-1}$
What is the energy band which includes the energy levels of the valence electrons called?
Valence band
What happens if the lowest level in the conduction band is lower than the highest level of the valence band?
Electrons from the valence band can move into the conduction band
What is the effect of electrons coming very close or overlapping in a solid?
Different energy levels with continuous variation form energy bands
What characteristic distinguishes metals from metallic conductors?
Low resistivity and high conductivity
What are the energy levels of the valence electrons called?
Valence levels
What happens if some of the electrons from the valence band gain external energy to cross the gap between the conduction band and the valence band?
They move into the conduction band and create vacant energy levels in the valence band
What is the lowest energy level in the conduction band called?
EC
What is the characteristic of an insulator in terms of its electrons?
There are no free electrons in the conduction band.
What creates the possibility of conduction in a material?
Vacancies in the valence band
What are Si and Ge classified as in terms of semiconductors?
Semiconductors with no energy gap
Study Notes
Electrical Conductivity of Solids
- Metals have very low resistivity and high conductivity.
- Semiconductors have conductivity between metals and insulators, with resistivity ranging from 10^(-4) to 10^4 ohm-meters.
Semiconductors
- Elemental semiconductors include Si and Ge.
- Currently available semiconductor devices are based on elemental semiconductors Si or Ge.
- Compound inorganic semiconductors include CdS and GaAs.
Insulators
- Insulators have high resistivity and low conductivity, with resistivity ranging from 10^4 to 10^11 ohm-meters.
Energy Bands
- The energy band including the energy levels of the valence electrons is called the valence band.
- The lowest energy level in the conduction band is called the conduction band edge.
- When the lowest level in the conduction band is lower than the highest level of the valence band, the solid is a conductor.
Electron Behavior
- When electrons come very close or overlap in a solid, they create the possibility of conduction in the material.
- If some electrons from the valence band gain external energy to cross the gap between the conduction band and the valence band, they can move to the conduction band, allowing conduction.
Characteristics of Solids
- Metals are distinguished from metallic conductors by their low resistivity and high conductivity.
- Insulators are characterized by their electrons being localized and not able to move freely.
- Semiconductors are distinguished from metals and insulators by their intermediate conductivity.
Learn about the broad classification of solids based on their electrical conductivity, including metals, semiconductors, and insulators. Understand the ranges of resistivity and conductivity that define each category.
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