Note 1 to entry: The four interrelated vector quantities, which obey Maxwell’s equations, are by convention:

• the electric field strength E,
• the electric flux density D,
• the magnetic field strength H,
• the magnetic flux density B.

Note 2 to entry: This definition of electromagnetic field is valid in so far as certain quantum aspects of electromagnetic phenomena can be neglected.

Note 3 to entry: An electromagnetic field can include static components, i.e. an electrostatic field and a magnetostatic field, and time-varying components representing electromagnetic waves.