Question

An electric current of 8 Amperes is measured across an area of $50c{m}^2$, then current density in this area is:

• A. Must be $1600A/m^2$
• B. Must be greater than or equal to $1600A/m^2$
• C. Must be less than or equal to $1600A/m^2$
• D. Cannot say

Answer 1

The correct option is B Must be greater than or equal to $1600A/m^2$

$i=jAcos\theta \Rightarrow jcos\theta =\frac{i}{A}=1600$
$cos\theta =\frac{1600}{j}\le 1$
$j\ge 1600$