Asked by: Colin Coulton

In order to generate a magnetic field that can be said to propagate, it is necessary to produce a changing field by turning on an electromagnet or removing a magnet from a magnetic shield such as a superconducting box. Changing magnetic fields are also produced around all radio transmitter antennas due to the changing current flowing in them.

When a magnetic field is changing, it is always accompanied by a transverse electric field, i.e., it is an electromagnetic wave. The relationships between changing magnetic and electric fields are summarized in the well-known Maxwell's equations.

Click here for a more detailed mathematical derivation and description.

The speed of electromagnetic waves is certainly known and is defined to be exactly 299,792,458 m/s in vacuum (same as the speed of light).

Answered by: Scott Wilber, President, ComScire - Quantum World Corporation

'Physics is mathematical not because we know so much about the physical world, but because we know so little; it is only its mathematical properties that we can discover.'**Bertrand Russell**

(*1872-1970*)

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