Volume 19: Pages 43-54, 2006
A Changing Electric Field Generates a Changing Magnetic Field, Which in Turn Will Generate a Changing Electric Field: Are the Electric and Magnetic Field Components Time out of Phase?
G. Mthombeni, A. F. Mulaba‐Bafubiandi
Extraction Metallurgy Department, Faculty of Engineering and the Built Environment, University of Johannesburg, Wits 2050, South Africa
Electromagnetic waves are used to transport energy and information from one region in space to another. The Scottish physicist James Clerk Maxwell (1831–1879) described electromagnetism using four equations: two Gauss's laws for electricity and for magnetism, Faraday's law, and a modified Ampère's law. In his honor these equations are known as Maxwell's equations. These equations are fundamentals of electromagnetism. Static electric and magnetic fields can be treated independently of each other. The situation is different as soon as the electric or the magnetic field varies with time. Then they cannot be treated independently of each other, because the changing electric field produces a changing magnetic field and the newly produced changing magnetic field produces a changing electric field, which is an electromagnetic wave. Therefore, considering the relationship given by Maxwell's equations, the electric and magnetic fields are not only space out of phase but also time out of phase, meaning that the one quantity is leading while the other is lagging. Ignoring the fundamental equations of electromagnetism would give an impression that the electric and magnetic fields are only spatially out of phase, and the fact that the one quantity is leading and the other lagging would not be clear. Therefore, based on the available mathematical evidence, it is suggested to fit the conventional representation of the electromagnetic field, which shows the electric field and the magnetic field at right angles to each other and in time phase, to the new representation, which would highlight the fact that the electric and magnetic fields are time out of phase.
Keywords: electromagnetic waves, microwave heating
Received: October 3, 2004; Published online: December 15, 2008