DOI:10.1049/jiere.1986.0095

出版商:IERE    

年代:1986

数据来源: IET

摘要:

The lecture begins with a brief account of the way Maxwell arrived at his celebrated equations, and describes an alternative approach in which the concept of displacement current, often a source of difficulty to the student, is not invoked.The main part of the lecture is devoted to a discussion of the physical interpretation of some of the results which can be deduced from these equations. The close connection between electromagnetic and mechanical phenomena is discussed; for example, the theory of the deformation of an electromagnetic cavity resonator is closely linked to the conservation of angular momentum in mechanics. A surprising phenomenon exhibited by waves on a water surface is found to have an equally surprising counterpart in electromagnetic surface waves. Although the most exciting results arise when Maxwell's equations are applied to the radio-frequency part of the spectrum, surprises can occur at very low frequencies, and an example is given.In the final part of the lecture, some simple quantum ideas are introduced, and the relationship between the quantum approach and the classical approach from Maxwell's equations is briefly discussed.

DOI:10.1049/jiere.1986.0119

出版商:IERE    

年代:1986

数据来源: IET

摘要:

The initial contribution of radio to navigation was the transmission of time signals and these became established the 1920s. Shipboard direction-finding equipment of the period was cumbersome but efforts to circumvent this drawback gave rise to a long-lasting radio/acoustic technique for determining distance. Experience with groundbased D/F as an aid to airship navigation in the 1914—18 war had taught important lessons and led to the evolution of the rotating-beacon type of system. Some prophetic inventions were published during the decade and the fourcourse radio range took practical shape.

DOI:10.1049/jiere.1986.0121

出版商:IERE    

年代:1986

数据来源: IET