现代物理    Vol.5 No.5 (September 2015)

电磁场的传播速度，评论“导线中交流电场时间延迟的测定”和“交变电场速度测量的物理原理”
EM Wave Propagation Speed, Comments on “Measurement of Time Delay of Alternating Electrical Field in Wires” and “Physical Principles of Measuring the Speed of Alternating Electrical Field”

作者: 郑翊 , 徐骋 , 牟晋君 ：圣克劳州立大学电子与计算机工程系，明尼苏达州，圣克劳德，美国;

关键词: 电磁场； 相速度； 时间延迟； 超光速； Electromagnetic Field； Time Delay； Phase Velocity； Superluminal Speed

摘要:
只有在没有反射或反射因素极小的情况下，在发射端和接收端电磁场的时间差可以用于计算电磁场从反射端到接收端的传播相速度。由于反射，测量到的合成波的相位是入射波和反射波相位的合成，由反射而引入的相位变化导致发射和接收端之间的同相位电磁波的时间差的移动。这种两点间的合成波的时间差由于反射既能增加也可能减小，在一定的情况下，时间差还可以是负数。由于忽视因反射而引起的相位差或时间差的变化，最近发表在《现代物理》上的两篇文章的作者们用带有反射的合成波的时间差计算电场传播速度，并和光在自由空间里传播相速度比较，进而在两篇文章中错误地宣称：“交变电场的速度超过光速20倍以上。”这两篇在《现代物理》上发表的文章是：“导线中交流电场时间延迟的测定”(现代物理，2015，5，29-34)和“交变电场速度测量的物理原理”(现代物理，2015，5，35-39)。此评论文章用理论和实验数据推翻其文章“超光速20倍”的结论。

Abstract: The time shift of an electromagnetic wave at a single frequency between a transmitter and a re-ceiver can be used to determine the phase velocity of the wave propagation only if there is no reflection at the receiver or the reflection is very small. The reflection adds additional phase shifts to the composted wave of an incident wave and a reflected wave so that the time difference of the composted wave is shifted between the transmitter and the receiver. This time difference may be either decreased or increased and even negative in a certain condition. Ignoring the phase shift and time shift induced by the reflection, the authors of two articles recently published on “Modern Physics” wrongly claim of “the speed of alternating electric field can be 20 times faster than the speed of light”. The two articles are: “Measurement of Time Delay of Alternating Electrical Field in Wires” (Modern Physics, 2015, 5, 29-34) and “Physical Principles of Measuring the Speed of Alternating Electrical Field” (Modern Physics, 2015, 5, 35-39). In this communication note, theory and experiments are presented to falsify their claim.

Abstract:

文章引用: 郑翊 , 徐骋 , 牟晋君 (2015) 电磁场的传播速度，评论“导线中交流电场时间延迟的测定”和“交变电场速度测量的物理原理”。 现代物理， 5， 114-123. doi: 10.12677/MP.2015.55015

参考文献

[1] 张操, 廖康佳, 樊京 (2015) 导线中交流电场时间延迟的测定. 现代物理, 5, 29-34.

[2] 张操, 廖康佳 (2015) 交变电场速度测量的物理原理. 现代物理, 5, 35-39.

[3] Shen, L.C. and Kong, J.A. (1995) Applied electromagnetism. 3rd Edition, PWS Publishing Company, Boston.

[4] Ulaby, F.T., Michielssen, E. and Ravaioli, U. (2010) Fundamentals of applied electromagnetics, 6/E. Prentice Hall, Upper Saddle River.

[5] Calculating the propagation delay of coaxial cable. http://www.gpssource.com/files/Cable-Delay-FAQ.pdf

[6] Round wire inductance calculator. http://chemandy.com/calculators/round-wire-inductance-calculator.htm

[7] Wang, R., Zheng, Y. and Yao, Y. (2004) Generalized Sagnac effect. Physical Review Letters, 93, Article ID: 143901.
http://dx.doi.org/10.1103/physrevlett.93.143901

[8] Wang, R.Y., Zheng, Y., Yao, A.P. and Langley, D. (2003) Modified Sagnac experiment for measuring travel-time difference between counter-propagating light beams in a uniformly moving fiber. Physics Latter A, 312, 7-10.
http://dx.doi.org/10.1016/S0375-9601(03)00575-9

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