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I was told that current has a direction but does not follow vector-laws, so it is a scalar quantity. That's okay. I thought it through Kirchoff's junction law: assume two currents joining at 90 deg, but they will not add vectorially, but algebraically.

Now, I am told that current density is a vector quantity. Solving for this, two current densities maybe added at 90 deg or 45 deg they will definitely give same result and will definitely not add vectorially.

So, why is current-density considered as vector?

$$i = j A$$ $i$ is current, $j$ is current-density, and $A$ is the area of cross-section

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  • $\begingroup$ See also physics.stackexchange.com/q/90995/25301 $\endgroup$
    – Kyle Kanos
    Mar 5 '19 at 14:02
  • $\begingroup$ Dividing scalar by scalar doesn't yield vector, I don't really know nor understand what's going on. I don't think I can be of any help to you at the moment, but if I ever find anything soon, I'll post. Good luck pal. $\endgroup$
    – TechDroid
    Mar 5 '19 at 14:11
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    $\begingroup$ @TechDroid thnx for help :) but as much i know, cross-section area is vector quantity.. $\endgroup$ Mar 5 '19 at 14:13
  • $\begingroup$ That shows how much more I need to learn. You're welcome by the way. But what's the direction element of cross-section area? $\endgroup$
    – TechDroid
    Mar 5 '19 at 14:20
  • $\begingroup$ @TechDroid perpendicular to the surface $\endgroup$ Mar 5 '19 at 14:21