# Difference between flux and current

1. Jan 30, 2006

### EroticNirvana

What is exactly the difference between flux and electric or magnetic current? Is there a precise logical difference? Could anyone give an accessible explanation?

I'm looking for a string theoretic explanation but someone moved this thread. I'm not very thankful for that.

Last edited: Jan 31, 2006
2. Jan 30, 2006

### EroticNirvana

i am foremost looking for a string theoretic explanation of this distinction.

3. Jan 31, 2006

### Kalimaa23

The relation between fluxes of fields and the currents/charges that give rise to them are basic mathematical/physical notions. If are not familiar with them, I do not think you will be able to handle String Theory.

4. Jan 31, 2006

### EroticNirvana

nonsense

That's like saying, just because you do not know what a leg and what a table top is you cannot understand what a table is. Of course you can explain what a table is; you just explain the totality of the table.

It so happens that I'm learning about string theory right now and I'm maybe better versed in it that you are. Please don't respond in a snotty manner when you're unable to answer a question.

5. Jan 31, 2006

### Gokul43201

Staff Emeritus
Dimitri is right, and he's a grad student in theoretical (high energy ?) physics. Furthermore, you do not explain fluxes and currents using string theory. That's like asking someone to calculate 2+3 using partial differential equations.

Fluxes and currents are representations. Any quantity that can be written as the surface intergral of a vector field is called the flux of that field through that surface. So, for instance, the electric current I, is the flux of the current density vector J.

Now a current is anything that can be written as a rate of flow of some quantity (eg : mass, charge, spin, probability). In the context of the above example, the electric current is also the rate of flow of charge.

So, in this example, we see that the same quantity represents a flux as well as a current. The reason for this is the continuity equation (a relation that says that a box will contain what it had at some time +/- what you put in/took out).

Last edited: Jan 31, 2006
6. Feb 2, 2006

### EroticNirvana

sure

Ok. But i'm studying string theory and I'm interersted in the connection between string theory and these concepts. Now that is a question that may be odd or awkward but that's the question I want an anwer to. So well, it may be tricky to override a person's intention with a question.

Given the veracity of string theory, a distinction (between flux and current) that makes sense in classical physics should make sense in string theory as far as classical physics is correct.

Anyhow, I happen to be familiar w/ these concepts. It's the connection to string theory that i'm inquireing about. I like simple explanation and if one is smart one tends to be able to provide one even for the most difficult subjects.

Last edited: Feb 2, 2006
7. Feb 12, 2006

### pinestone

Take a look at the Aharonov-Bohm effect- As I understand it, seems to describe flux as a vector quantity, ie. "voltage".

Last edited: Feb 12, 2006
8. Feb 12, 2006

### pervect

Staff Emeritus
I think you need to provide more detail of exactly what it is you are interested in.

I think of a generalized current as the rate of flow of a generalized charge. A conserved charge must obey a conservation law when associated with its conserved current, the rate of flow of charge.

(see http://en.wikipedia.org/wiki/Conserved_current)

Conservation of generalized charge is a consequence of symmetries (see http://en.wikipedia.org/wiki/Noether's_theorem )

Electric current is one example of a specific sort of current that arises in E&M that results from the conservation laws associated with charge, which arise from gauge invariance symmetry in E&M.

Flux is associated with a vector field. Gauss's law for the electric field (a vector field) shows that certain closed flux intergals are also associated with conserved charges.

9. Feb 16, 2006

### EroticNirvana

the distinction in terms of string theory

I'm just asking for an explanation of the distinction between electric current and flux in a string theoretical terminology. That's quite a difficult task, but that's what I'm asking for.

10. Feb 3, 2011

### luciferr

ITS EASY -

CURRENT - Rate of flow

FLUX - Amount of flow

It seems like people try to make it more complicated to make themselves feel smarter or something. So annoying.