The current density j flowing through a conductor of cross-sectional area A carrying current I (with current normal to the area) is

1. Current density is current per unit area normal to the flow. 2. By definition $j = I/A$, with SI unit $\text{A m}^{-2}$. 3. Rearranging gives $I = jA$, consistent with the text. 4. $IA$ and $A/I$ invert the definition; $I/A^2$ has wrong units. _Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.4_