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A bold capital D, the electric field with polarisation folded in.
Also known as: Electric flux density, D field, Displacement field
D is the electric analogue of B: it accounts for a dielectric's own polarisation so that Gauss's law can be written in terms of free charge alone. Its existence is why a capacitor's capacitance changes when you slide a slab of plastic between the plates.
Denotes electric displacement, combining the electric field with the material's polarisation.
Contexts: Laboratory
Lets Gauss's law be written using free charge alone, with the bound charge of the dielectric absorbed into D.
Contexts: Laboratory
Pairs with E exactly as B pairs with H, which is the symmetry the four Maxwell fields are built on.
Contexts: Laboratory
A bold capital letter D, a vertical stroke with a bowed curve joining its top and bottom on the right.