Current body is a admeasurement of the body of an electric current. It is authentic as a agent whose consequence is the electric accepted per cross-sectional area. In SI units, the accepted body is abstinent in amperes per aboveboard metre.
I = \vec{J} \cdot \vec{A}
where I is accepted in the conductor, J is the accepted density, and A is the cross-sectional area. The dot artefact of the two agent quantities (A and J) is a scalar that represents the electric current.
Current body (current per assemblage area) J in a actual is proportional to the application σ and electric acreage E in the medium:
J =\sigma E \,
Instead of conductivity, a alternate abundance alleged resistivity ρ, can be used:
J = {E \over \rho}
Conduction in semiconductor accessories may action by a aggregate of alluvion and diffusion, which is proportional to circulation connected D and allegation body αq. The accepted body is then:
J =\sigma E + D q \nabla n ,
with q getting the elementary allegation and n the electron density. The carriers move in the administration of abbreviating concentration, so for electrons a absolute accepted after-effects for a absolute body gradient. If the carriers are holes, alter electron body n by the abrogating of the aperture body p.
In beeline anisotropic materials, σ, ρ and D are tensors.
In beeline abstracts such as metals, and beneath low frequencies, the accepted body beyond the aqueduct credible is uniform. In such conditions, Ohm's law states that the accepted is anon proportional to the abeyant aberration amid two ends (across) of that metal (ideal) resistor (or added ohmic device):
I = {V \over R} \, ,
where I is the current, abstinent in amperes; V is the abeyant difference, abstinent in volts; and R is the resistance, abstinent in ohms. For alternating currents, abnormally at college frequencies, derma aftereffect causes the accepted to advance anyhow beyond the aqueduct cross-section, with college body abreast the surface, appropriately accretion the credible resistance.
I = \vec{J} \cdot \vec{A}
where I is accepted in the conductor, J is the accepted density, and A is the cross-sectional area. The dot artefact of the two agent quantities (A and J) is a scalar that represents the electric current.
Current body (current per assemblage area) J in a actual is proportional to the application σ and electric acreage E in the medium:
J =\sigma E \,
Instead of conductivity, a alternate abundance alleged resistivity ρ, can be used:
J = {E \over \rho}
Conduction in semiconductor accessories may action by a aggregate of alluvion and diffusion, which is proportional to circulation connected D and allegation body αq. The accepted body is then:
J =\sigma E + D q \nabla n ,
with q getting the elementary allegation and n the electron density. The carriers move in the administration of abbreviating concentration, so for electrons a absolute accepted after-effects for a absolute body gradient. If the carriers are holes, alter electron body n by the abrogating of the aperture body p.
In beeline anisotropic materials, σ, ρ and D are tensors.
In beeline abstracts such as metals, and beneath low frequencies, the accepted body beyond the aqueduct credible is uniform. In such conditions, Ohm's law states that the accepted is anon proportional to the abeyant aberration amid two ends (across) of that metal (ideal) resistor (or added ohmic device):
I = {V \over R} \, ,
where I is the current, abstinent in amperes; V is the abeyant difference, abstinent in volts; and R is the resistance, abstinent in ohms. For alternating currents, abnormally at college frequencies, derma aftereffect causes the accepted to advance anyhow beyond the aqueduct cross-section, with college body abreast the surface, appropriately accretion the credible resistance.
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