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Jan29-13, 09:58 PM
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Quote Quote by cepheid View Post
EDIT: I do see now from you original post that some sources justify the use of the term "flux density" for B, by noting that when you integrate it over an area, you get the magnetic flux. Fair enough.
I'm not an EM guy, but you might find it easier to understand the words in for something like heat flow.

"Flux" is the total amount of heat flowing through a surface (measured as heat energy / second, i.e. power in watts)

"Flux density" is the flux per unit area, or sometimes the amount of heat generated per unit volume (for example heating something in a microwave oven, or heat generated by nuclear reactions).

FWIW, temperature is a scalar field (which is simpler to visualize than the vector fields in EM) and the direction of the flux is therefore the gradient of the temperature field. If you visualize a temperature distribution on a plane by drawing a contour map, the flux direction is at right angles to the temperature contour lines, and the magnitude of the flux density is higher where the temperature contours are closer together.