## Relation between Current density, conductivity and electric field: Point Form of Ohm’s law

As we have already derived and discussed the Ohm’s law. Let us derive and discuss the point form of Ohm’s law which is basically the relation between current density (J), conductivity (σ) and electric field (E).

As current  is related with drift velocity by relation

I=n Aevd

I = n Ae(eE/m)              ( because vd=eE/m)

I   = nAe2E/m

Or                  I/A=ne2 E/m                            (1) Continue reading “Relation between Current density, conductivity and electric field: Point Form of Ohm’s law”

## Current Density, Conductance And Electrical Conductivity

Current density at a point in a conductor is defined as the amount of current flowing per unit area of the conductor around that point provided the area is held in a direction normal to the current.

Let I be the current distributed uniformly across a conductor of cross-sectional area A. The magnitude of the current density for all points on that cross-section of the conductor is

J=I/A

Current density is a vector quantity. Its direction is the direction of motion of positive charge. Continue reading “Current Density, Conductance And Electrical Conductivity”