and the magnetic field B have the same dimension. This amounts to a factor of c between how B is defined in the two unit systems, on top of the other differences. (The same factor applies to other magnetic quantities such as H and M.) For example, in a planar light wave in vacuum, in Gaussian units, while in the ISQ. Polarization, magnetization There are further differences between Gaussian system and the ISQ in how quantities related to polarization and magnetization are defined. For one thing, in the Gaussian system, all of the following quantities have the same dimension: E, D, P, B, H, and M. A further point is that the electric and magnetic susceptibility of a material is dimensionless in both Gaussian system and the ISQ, but a given material will have a different numerical susceptibility in the two systems. (Equation is given below.) List of equations This section has a list of the basic formulae of electromagnetism, given in both the Gaussian system and the International System of Quantities (ISQ). Most symbol names are not given; for complete explanations and definitions, please click to the appropriate dedicated article for each equation. A simple conversion scheme for use when tables are not available may be found in Ref. All formulas except otherwise noted are from Ref. Maxwell's equations Here are Maxwell's equations, both in macroscopic and microscopic forms. Only the "differential form" of the equations is given, not the "integral form"; to get the integral forms apply the divergence theorem or Kelvin–Stokes theorem. Other basic laws Dielectric and magnetic materials Below are the expressions for the various fields in a dielectric medium. It is assumed here for simplicity that the medium is homogeneous, linear, isotropic, and nondispersive, so that the permittivity is a simple constant. where E and D are the electric field and displacement field, respectively; P is the polarization density; is the permittivity; is the permittivity of vacuum (used in the SI system, but meaningless in Gaussian units); is the electric susceptibility The quantities and are both dimensionless, and they have the same numeric value. By contrast, the electric susceptibility and are both unitless, but have different numeric values for the same material: Next, here are the expressions for the various fields in a magnetic medium. Again, it is assumed that the medium is homogeneous, linear, isotropic, and nondispersive, so that the permeability is a simple