The SI unit of charge density depends on the type of charge density being considered. There are three main types:
1. Volume Charge Density
Volume charge density is the amount of electric charge per unit volume. Its SI unit is coulombs per cubic meter (C/m³). This is consistent across multiple sources, including Wikipedia's definition of volume charge density https://en.wikipedia.org/wiki/Charge_density and various educational websites like Unacademy https://unacademy.com/content/charge-density-formula/. It can also be expressed as farads per cubic meter (F/m³).
- Example: Imagine a cubic meter of material with a total charge of 5 Coulombs. The volume charge density would be 5 C/m³.
2. Surface Charge Density
Surface charge density measures the amount of electric charge per unit area. Its SI unit is coulombs per square meter (C/m²). This is confirmed by sources such as Vedantu https://www.vedantu.com/formula/surface-charge-density-formula and toppr https://www.toppr.com/ask/question/the-si-unit-of-surface-charge-density-is/.
- Example: A square meter of a charged surface holding 2 Coulombs of charge has a surface charge density of 2 C/m².
3. Linear Charge Density
Linear charge density describes the charge per unit length. Its SI unit is coulombs per meter (C/m). While not explicitly stated in all references, it's implicitly defined by the other charge density types. The formula for linear charge density (λ = q/l, where q is charge and l is length) implies the unit of C/m.
- Example: A wire one meter long carrying a charge of 1 Coulomb has a linear charge density of 1 C/m.
In summary, the SI unit of charge density is not a single value but depends on whether we're considering volume, surface, or linear charge distribution.
