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what is the difference between electric flux and charge?

both have same units(coulombs) and symbol q or Q

but gauss' law uses flux density (D) and not charge

also if phi(F) is magnetic flux then what is component like 'charge' in magnetism?

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- #1

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what is the difference between electric flux and charge?

both have same units(coulombs) and symbol q or Q

but gauss' law uses flux density (D) and not charge

also if phi(F) is magnetic flux then what is component like 'charge' in magnetism?

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jim hardy

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sometimes i resort to the ridiculous to get my thinking straight,,,

i think, as previous poster said, the equations do not make it intuitively obvious whether they are describing total flux or flux density. so try this simple thought then go back to your text and see if we missed some subtlety..,

imagine a closed gaussian surface surrounding a skunk.

if that gaussian surface has an area of just one square meter

there'll be an intense field of

if one moves his gaussian surface further out, for the obvious reason, and repeats his closed surface integral, well, it'll be a more comfortable measurement to make even if more tedious.

If the new gaussian surface has an area of 1,000 sq meters the field

But the charge enclosed is the same - one skunk..

one skunk per sq meter is too intense, one per acre is tolerable.

i hope i did not mis-understand your question.

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Another way to think of this (it turns out to be the same inverse square law) is gravity.If the new gaussian surface has an area of 1,000 sq meters the fieldstrengththere is attenuated a thousandfold. The same lepew is spread over a thousand times the area.

But the charge enclosed is the same - one skunk..

one skunk per sq meter is too intense, one per acre is tolerable.

i hope i did not mis-understand your question.

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jim hardy

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indeed if E is volts/meter

think of point source and inverse square law

think of point source and inverse square law

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Integrating that density over the entire surface(that field lines are penetrating) gives the number of field lines penetrating the surface, and that is exactly what the expression for electric flux gives.

This is what flux represents. Good ANALOGY is flow of water. If you ask yourself, how many particles are flowing through some random chosen closed surface, you will get the flux through that surface.

But this is analogy, and this should only HELP you get your intuition, but do not consider ELECTRIC flux as flow of particles.

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dlgoff

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[URL]http://courses.science.fau.edu/~rjordan/rev_notes/images/22.1.gif[/URL]

If you have a QuickTime player, this animation explains it very well:

"courses.science.fau.edu/~rjordan/rev_notes/movies/EFM06AN1.MOV"[/URL]

[QUOTE]This video clip was obtained from the "Core Concepts in Physics" CD-ROM produced by Saunders College Publishing. They are to be used for Educational Purposes only; do not copy.[/QUOTE]

[URL]http://courses.science.fau.edu/~rjordan/rev_notes/22.1.htm"[/URL]

If you have a QuickTime player, this animation explains it very well:

"courses.science.fau.edu/~rjordan/rev_notes/movies/EFM06AN1.MOV"[/URL]

[QUOTE]This video clip was obtained from the "Core Concepts in Physics" CD-ROM produced by Saunders College Publishing. They are to be used for Educational Purposes only; do not copy.[/QUOTE]

[URL]http://courses.science.fau.edu/~rjordan/rev_notes/22.1.htm"[/URL]

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Flux is the sum total of all the influences on your wallet while charge is the contents therein.

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Electric flux and charge are totally different. Electric charge is physical charge, electric flux is field lines generated by charges.

what is the difference between electric flux and charge?

both have same units(coulombs) and symbol q or Q

but gauss' law uses flux density (D) and not charge

also if phi(F) is magnetic flux then what is component like 'charge' in magnetism?

Electric charge unit is coulomb, Flux is more a force kind of thing that the unit is V/m. As in volt per meter. It is a force. Usually we talk about flux as field lines where you see pictures of curve lines from a +ve charge to a -ve charge.

In math point of view, Flux lines are vector fields where every point in space has it's own vector with amplitude and direction as a function.

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Flux is not a flow of charges. Flux is generated by charges. It is a force field. Look at any book for Calculus III multi-variables under the topic of Vector Field and you'll see example of electric field and explanation of static electric field is a conservative field that is path independent.

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What you are referring to is only a specific condition where there is only a point charge and the fields are radial fields that generated at the point of charge and radiate out evenly in all direction and the intensity diminish as inverse square of distance from the point.

Integrating that density over the entire surface(that field lines are penetrating) gives the number of field lines penetrating the surface, and that is exactly what the expression for electric flux gives.

This is what flux represents. Good ANALOGY is flow of water. If you ask yourself, how many particles are flowing through some random chosen closed surface, you will get the flux through that surface.

But this is analogy, and this should only HELP you get your intuition, but do not consider ELECTRIC flux as flow of particles.

In real life, we can have distribution of charges, moving charges and they form complicated shape. that is where vector fields come into play. From the distribution of charges, you find the sum of the fields of all charges at any point and get the resultant vector field of that point.

For point charge:

[tex]\vec E =\frac {q\hat r}{4\pi \epsilon_0 r^2}\;\hbox {where }\; \hat r \;\hbox { is the radial vector from the center to the point and }\; r\;\hbox { is the distance from the center.}[/tex]

For a distribution of n charges:

[tex] \vec E = \sum_{i=1}^n \frac {q\hat r_i}{4\pi \epsilon_0 r_i^2}\;\hbox { where }\;\hat r_i \;\hbox { is the vector from the i^th charge to the point.}[/tex]

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thanks the skunk theory helped....also thank you for the video...imagine a closed gaussian surface surrounding a skunk.

if that gaussian surface has an area of just one square meter

there'll be an intense field oflepewemanating from it.

if one moves his gaussian surface further out, for the obvious reason, and repeats his closed surface integral, well, it'll be a more comfortable measurement to make even if more tedious.

If the new gaussian surface has an area of 1,000 sq meters the fieldstrengththere is attenuated a thousandfold. The same lepew is spread over a thousand times the area.

But the charge enclosed is the same - one skunk..

one skunk per sq meter is too intense, one per acre is tolerable.

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