Formal Statement of The Law
See also: Continuity equationVector calculus can be used to express the law in terms of charge density ρ (in coulombs per cubic meter) and electric current density J (in amperes per square meter):
The term on the left is the rate of change of the charge density ρ at a point. The term on the right is the divergence of the current density J. The equation equates these two factors, which says that the only way for the charge density at a point to change is for a current of charge to flow into or out of the point. This statement is equivalent to a conservation of four-current.
Read more about this topic: Charge Conservation
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