Answer / harish e

current is determined based on the current density of the material.
If u are choosing aluminum as the conductor then the current density would be almost .8.Then we get
current density, j = current/ square mm
then , sqmm = current / current density.
in this way we can calculate current
current density for copper is 1.2 . we see that cooper being better conductor would need lesser cross section of the conductor compared to aluminium.

Answer / santosh nanda

Current is calculated from Current Density Formula

In the field of electromagnetism, Current Density is the measurement of electric current (charge flow in amperes) per unit area of cross-section (m2). This is a vector quantity, with both a magnitude (scalar) and a direction.

J = I/A

J = current density in amperes/m2

I = current through a conductor, in amperes

A = cross-sectional area of the conductor, m2

For Ex:
The current through the conductor is I = 6 mA = 0.006 amperes (or 6 x 10-3 amps). The area of the wire is A = 4 mm2 = 0.004 m2 (or 4 x 10-3 m2). Use the equation for current density.

J = I/A

J = 0.006 amps/0.004 m2

J = 1.5 amps/m2

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