Conductance is the ability of a material to conduct electric current. It is the reciprocal of resistance and is measured in Siemens (S).
Here's how conductance works in semiconductors and conductors:
Conductors:
* High Conductance: Conductors have a large number of free electrons, which can easily move throughout the material and carry current. This results in high conductance and low resistance.
* Metals: Most metals are excellent conductors due to their atomic structure, where electrons in the outermost shell are loosely bound and can move freely.
* Mechanism: When a voltage is applied across a conductor, the free electrons flow through the material, creating an electric current.
Semiconductors:
* Intermediate Conductance: Semiconductors have fewer free electrons than conductors, but more than insulators. This leads to moderate conductance and resistance.
* Silicon and Germanium: Common semiconductors used in electronics.
* Mechanism: Semiconductors conduct current primarily through two mechanisms:
* Intrinsic Conduction: At higher temperatures, some valence electrons gain enough energy to break free from their bonds and become free electrons.
* Extrinsic Conduction: By adding impurities (doping) to semiconductors, we can control their conductivity.
* N-type: Impurities with extra electrons increase the number of free electrons, resulting in better conductivity.
* P-type: Impurities with missing electrons create "holes," which act like positive charge carriers, increasing conductivity.
In Summary:
| Material Type | Conductance | Resistance | Explanation |
|---|---|---|---|
| Conductor | High | Low | Large number of free electrons, easily conducting current |
| Semiconductor | Moderate | Moderate | Fewer free electrons than conductors, but more than insulators; controlled conductivity |
Key Differences:
* Number of free electrons: Conductors have many free electrons, while semiconductors have fewer.
* Energy required for conduction: Conductors require less energy to conduct current, while semiconductors require more.
* Controllability: The conductivity of semiconductors can be controlled by doping, while the conductivity of conductors is generally fixed.
Understanding the difference in conductance between semiconductors and conductors is crucial for various electronic applications. Semiconductors are used in transistors, diodes, and other electronic devices, while conductors are used for wires, cables, and other components that carry electrical signals.
