Engineering Science 1021A/B Lecture Notes - Lecture 36: Drift Velocity, Microstructure
17 May 2018
School
Department
Professor
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Conductivity of a material:
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Because
𝑒
is a constant, this equation implies that we can influence the
conductivity of a material by either:
changing the number of charge carriers
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influencing their mobility
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Charge carriers
In metals and semiconductors and many insulators, electrons are the
charge carriers
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Ions are the charge carriers in ionic compounds
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The mobility of the charge carriers depends on
atomic bonding•
lattice defects•
microstructure•
diffusion rates (in ionic conductors)•
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Numerical Examples
Calculate the number of charge carriers in a 1mm diameter copper wire 1m long
Since the valence of copper is one, there is one carrier per atom
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1.
Calculate the drift velocity in the wire under an applied voltage of 12V. (σ = 5.98
×107 Ω-1·m-1)
2.
From the last example, the wire contains 6.65×1019 carriers
Electrical Conductivity
