CONVECTION & CONDUCTION CURRENT DENSITY

[mtkee2003]

hi

in electromagnetics theory we have two concepts:
1- CONVECTION CURRENT DENSITY (J)
2- CONDUCTION CURRENT DENSITY (J)

as mentioned above , both of them have same abbreviation (J). now i

want to know what is the difference between these concepts?

with best regards.

 

[alekxv]

Hi,
Let me try to explain it the better I know.

First of all the letter used ( J ) is a letter to mean current density so this is why you see it in both types of currents.
Convenction Current Density is a relation of the current density to the speed of volumetric charge density in a certain point. Simply put is the amount of current passing in a time t through a surface S. This surface is always perpendicular to the current flow. For example: If you wanted to increase the traffic in a tunnel, you will do it by increasing the speed of the cars or by increasing the number of cars (if this could be done) putting one on top of another. (ie increasing the density per cubic inch)

Conduction Current Density refers to the amount of current (charges) flowing on the surface of a conductor (conduction band) in a time t. This surface is always parallel to the current flow. This phenomenon is what gives a material its conductive nature and this happens because the energy gap between the valency band of the material and its conduction band is narrow. A wide energy gap causes the electrons not to have enough energy to jump to the conduction band and makes this material an isolator.

Hope this will help to answer your question