Current Density Conductance and Conductivity

Current Density Conductance and Conductivity:

Current Density (J)- It is defined as the amount of current flowing per unit area of the conductor at a particular point, provided the area is held perpendicular to the direction of the current.

Let ‘I’ be the current distributed uniformly over the cross-sectional area A of the conductor, then

J = I/A

Current density, J is a vector quantity. Its direction is the direction of motion of the positive charge. The S.I. unit of current density if ampere/metre2.

We know, I = nAeνd
⇒ I/A = neνd
⇒ J = neνd

Conductance (G)- The inverse of resistance is called conductance of the conductor i.e.

G = 1/R

The S.I. unit of conductance is mho or siemen (S).

Conductivity (σ)- The inverse of resistivity is called the conductivity of the conductor i.e.

σ = 1/ρ

The S.I. unit of conductivity is mho-m-1 or siemen-m-1.

Relation between Current Density Conductance and Conductivity:

We know, I = nAeνd ————(I)
But, νd = Eeτ/m —————–(II)
Put (II) in (I)
⇒ I = nAe (Eeτ/m)
⇒ I = nAe2Eτ/m
⇒ I/A = ne2τ/m x E
⇒ J = ne2τ/m x E
But, ne2τ/m = 1/ρ
⇒ J = 1/ρ x E
But, 1/ρ = σ = conductivity of the conductor
⇒ J = σE
It is microscopic form of Ohm’s Law.

Coulomb’s LawHeisenberg Uncertainty Principle
Capacitor and its PrincipleDielectric Properties of Solids
Parallel Plate CapacitorPreparation of Lyophobic Sols
Coherent and Incoherent SourcesChemical Thermodynamics– NIOS

Comments (No)

Leave a Reply