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>> Current Density
Current density ‘’ defined as current flowing per unit cross-section area, is a vector quantity. Its direction is the same as that of current and it has following relation with current.
Alt txt : current-density
I = where d is a small area element of the chosen cross-section.
Integration is carried over the whole cross-section. Hence current may also be defined as the flux of current density vector through a cross-sectional area.
If in the above figure, angle between , current density vector and , the are vector of cross section is 60o, current i is 10A and area of given cross section is 2 × 10–6 m2. What is magnitude of current density.
I = |||| cos q (as is constant over the cross-section, = A)
Þ || = 1 × 107 A/m2