> [!summary] Current density is the amount of current per unit area. > **Key Equation:** > Current density: $\vec{J}=\frac{I}{A}=\frac{qnv_{d}A}{A}=qnv_{d}$ >[!info]+ Read Time **⏱ 1 min** # Definition Current density is the amount of [[Current|current]] per unit area. Sometimes, in defining current density, we assume the current in a general sense. Mathematically defined below as the number of charges per area, taking into account the [[Current#Drift Velocity|drift velocity]]. $\vec{J}=\frac{I}{A}=\frac{qnv_{d}A}{A}=qnv_{d}$ ![[cd_1.png]] [^2]