Chapter 18.1

# Chapter 18.1 - Electrical properties Electrical conduction...

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1 MSE 2090: Introduction to Materials Science Chapter 18, Electrical Conductivity Electrical properties ¾ Electrical conduction • How many moveable electrons are there in a material (carrier density) ? How easily do they move (mobility) ? ¾ Semiconductivity Electrons and holes Intrinsic and extrinsic carriers Semiconductor devices: p-n junctions and transistors ¾ Conduction in polymers and ionic materials ¾ Dielectric behavior Optional reading: 18.14, 18.15, 18.21, 18.23-18.25

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Basic laws and electrical properties of metals (I) When an electrical potential V [volts, J/C] is applied across a piece of material, a current of magnitude I [amperes, C/s] flows. In most metals, at low values of V, the current is proportional to V, and can be described by Ohm's law : I = V/R where R is the electrical resistance [ohms, Ω , V/A]. R depends on the intrinsic resistivity ρ of the material [ Ω - m] and on the geometry (length l and area A through which the current passes): R = ρ l/A In most materials (e.g. metals), the current is carried by
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