What exactly is Electric Flux Density?

In summary, flux density is defined as D= ε E or ∇.D=ρ, but it is not the same as the symbol "phi" used in the Wikipedia article on electric flux. D and "phi" have different units and do not represent the same quantity. The terminology of "electric flux" is simply historical and they do not have the same physical meaning.
  • #1
iVenky
212
12
We define flux density as D= ε E right?
or even ∇.D=ρ

But I can't link the above with what is given in the wiki where they have used the symbol "phi"

http://en.wikipedia.org/wiki/Electric_flux


What is the difference between D and symbol "phi"?

I would be really happy if you could help me as I am new to EMF.

Thanks a lot. :)
 
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  • #2
[itex]D[/itex] and [itex]\Phi[/itex] are nothing alike, don't have the same units, don't represent different aspects of the same quantity, nothing. That they share the words "electric flux" in them is simply misleading, but the roots of this terminology are historical, I'm sure.
 
  • #3
What I read was D is the no of electric lines which seems to be same as [itex]\phi[/itex]. What is the exact physical meaning of D ?

Thanks a lot.
 

1. What is the definition of Electric Flux Density?

Electric Flux Density, also known as electric displacement, is a measure of the electric field strength per unit area of a surface. It is represented by the symbol D and is measured in units of coulombs per square meter (C/m²).

2. How is Electric Flux Density different from Electric Field?

Electric Flux Density and Electric Field are closely related but represent different concepts. Electric Field measures the force exerted by an electric charge on another charge, while Electric Flux Density measures the amount of electric displacement per unit area of a surface.

3. What is the formula for calculating Electric Flux Density?

The formula for Electric Flux Density is D = Q/ΔA, where Q is the total charge enclosed by a surface and ΔA is the surface area. This formula is based on Gauss's Law, which states that the electric flux through a closed surface is equal to the charge enclosed by the surface divided by the permittivity of the medium.

4. How is Electric Flux Density used in practical applications?

Electric Flux Density is commonly used in the design and analysis of electrical systems, such as capacitors and transmission lines. It is also used in the study of dielectric materials, which are materials that can store and transmit electric energy.

5. Can Electric Flux Density be negative?

Yes, Electric Flux Density can be negative. A negative value indicates that the electric displacement is in the opposite direction of the electric field. This can occur in cases where the electric field is changing rapidly, such as near a moving charge or in an electromagnetic wave.

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