# What is flux?

1. ### HeilPhysicsPhysics

16
I don't understand what is the meaning of "flux" .I just know it has some relation between eletromagnetism.Please explain what is flux to me.

### Staff: Mentor

It could mean field lines (e.g. magnetic flux) per unit area or flow (photons) per unit area.

Or generally flux is the rate of transfer of fluid, particles, or energy across a given surface.

10
4. ### Gokul43201

11,141
Staff Emeritus
A flux is the value of the surface integral of any vector field. If the field is constant over the area of interest, the flux is simply the product of the field and the area. Conversely, the magnitude of the field is given by the flux per unit area.

5. ### Andrew Mason

6,876
Provided the area and field are perpendicular, of course (the surface integral being the integral of the dot product of the field and the area over the surface).

AM

6. ### Gokul43201

11,141
Staff Emeritus
Dot products are products too!!

Yes, I should have been more clear. Thanks for fixing that.

7. ### sharks

837
An easier way of visualizing this: Flux is surface bombardment rate.