# What does current density mean?

1. Apr 8, 2016

### AeroKaro

1. The problem statement, all variables and given/known data
Current density is the amount of current per cross sectional of flow. I'm having trouble wrapping my head around this definition. Surface charge or volume charge I understand better since they are almost analogous to the density we all understand (amount of matter/charge per unit area/volume/length). Current is something that's moving and its a little harder for my intuition to understand this. Could anyone please give any examples or anything to understand this concept better?

2. Relevant equations

3. The attempt at a solution

2. Apr 8, 2016

### AeroKaro

while doing some reading, I have though of another question, I see a lot of discussion about currents having with time. That seems all well but is there also such thing as a current changing in position? I was thinking if the wire was not uniform like the radius changes.

3. Apr 9, 2016

### ehild

The current is the whole charge flowing through a cross-section of a wire or any conductor in unit time. The current density is the current crossing perpendicularly a unit area in unit time. The current density is a vector, it has direction in addition to magnitude, and it can depend on place.