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Determining quantities as vectors or not

  1. Mar 4, 2014 #1
    Why are some quantities vectors while others aren't? For example, we can calculate both current and current density, but why do we only consider current density to be a vector and current a scalar quantity? Is it a purely arbitrary convention or is it something more mathematically fundamental? I understand vectors like forces and displacement have directions and magnitudes associated with them, but I don't quite understand why we don't do the same thing for quantities like current? Is it to simplify equations only?
  2. jcsd
  3. Mar 4, 2014 #2
    Current is a vector. The difference between current and current density is the dimensions of the vector. Current density is current per cross sectional area, or number of charges moving through a volume, while current is descriptive of charges moving along a line.
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