# Understanding Flux: The Measure of Field Lines Passing Through a Surface

• B
• rudransh verma
In summary, the equation Phi = int(E.da) represents the measure of the number of field lines passing through a surface, with the field strength being proportional to the density of field lines per unit area. This is analogous to the rate of flow of water, where the volume does not actually flow. The justification for this equation is based on the dot product between the electric field and the infinitesimal area, taking into account the angle between the two.
weirdoguy said:
Because without it formula for flux would not be useful. In most cases the reason that definitions look the way they look is just this - they are useful. You can define whatever you want, you can try to define a flux without E, or with E3 or with Eπ. Do what you want, but those definitions would be useless. I think you are wasting your time trying to dig in this issue too much. You should focus on where this definition of flux is used - and it's used in Gauss' theorem.
I missed your post. Only now I am looking

<h2>1. What is flux?</h2><p>Flux is a measure of the flow of a physical quantity through a given surface. In the context of field lines, flux represents the number of field lines passing through a surface.</p><h2>2. How is flux calculated?</h2><p>Flux is calculated by taking the dot product of the field vector and the surface vector. This means multiplying the magnitude of the field by the component of the field that is perpendicular to the surface.</p><h2>3. What is the unit of flux?</h2><p>The unit of flux depends on the physical quantity being measured. For example, in the case of magnetic flux, the unit is Weber (Wb), while electric flux is measured in Coulombs (C).</p><h2>4. What does a high flux value indicate?</h2><p>A high flux value indicates a large number of field lines passing through the surface. This can be interpreted as a strong or dense field in the region.</p><h2>5. How is flux related to Gauss's Law?</h2><p>Gauss's Law states that the total flux through a closed surface is equal to the charge enclosed by that surface divided by the permittivity of the medium. This means that flux can be used to calculate the electric field strength at a given point, or the charge enclosed by a surface if the electric field is known.</p>

## 1. What is flux?

Flux is a measure of the flow of a physical quantity through a given surface. In the context of field lines, flux represents the number of field lines passing through a surface.

## 2. How is flux calculated?

Flux is calculated by taking the dot product of the field vector and the surface vector. This means multiplying the magnitude of the field by the component of the field that is perpendicular to the surface.

## 3. What is the unit of flux?

The unit of flux depends on the physical quantity being measured. For example, in the case of magnetic flux, the unit is Weber (Wb), while electric flux is measured in Coulombs (C).

## 4. What does a high flux value indicate?

A high flux value indicates a large number of field lines passing through the surface. This can be interpreted as a strong or dense field in the region.

## 5. How is flux related to Gauss's Law?

Gauss's Law states that the total flux through a closed surface is equal to the charge enclosed by that surface divided by the permittivity of the medium. This means that flux can be used to calculate the electric field strength at a given point, or the charge enclosed by a surface if the electric field is known.

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