Electromagnetism is the combination of electrostatic and magnetic forces. It is the force between charged particles, such as the force between two electrons or the force between two current carrying wires. At the heart of this theory is the notion of an electromagnetic field, a phenomenon that can occur in one of two states: stationary or dynamic.

A stationary electromagnetic field stays bound to its origin. Examples of stationary fields are the magnetic field around a current carrying wire or the electric field between the plates of a capacitor.

A dynamic electromagnetic field propagates away from its origin in the form of a wave. These waves travel at c and exist in a wide spectrum of wavelengths. Examples of dynamic fields are radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays and gamma rays.