After finished this lesson student will able to #Say electrical resistivity. #.Say Electrical conductivity. # Say Resistors or with uniform cross-section.

• After finished this lesson student will able to

• #Say electrical resistivity.• #.Say Electrical conductivity .• # Say Resistors or with uniform cross-section.

Electrical resistivity

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Electrical conductivity

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Resistors or with uniform cross-section

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General definition

• The above definition was specific to resistors or conductors with a uniform cross-section, where current flows uniformly through them. A more basic and general definition starts from the fact that an electric field inside a material makes electric current flow. The electrical resistivity ρ is defined as the ratio of the electric field to the density of the current it creates:

• where• ρ is the resistivity of the conductor material

(measured in ohm metres, Ω m),⋅ ⋅• E is the magnitude of the electric field (in volts

per metre, V m⋅ −1),• J is the magnitude of the current density (in

amperes per square metre, A m⋅ −2),

Causes of conductivity

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• Filling of the electronic Density of states in various types of materials at equilibrium. Here the vertical axis is energy while the horizontal axis is the Density of states for a particular band in the material listed. In metals and semimetals the Fermi level EF lies inside at least one band. In insulators and semiconductors the Fermi level is inside a band gap; however, in semiconductors the bands are near enough to the Fermi level to be thermally populated with electrons or holes.

Task

• Give Explanation electrical resistivity.

• Say formula Resistors or with uniform cross-section.

• What is Electrical conductivity?

Thanks to all