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J. Electromagnetic Analysis & Applications, 2010, 2, 677-678 doi:10.4236/jemaa.2010.212089 Published Online December 2010 (http://www.SciRP.org/journal/jemaa) Copyright © 2010 SciRes. JEMAA Comments Concerning Measurements and Equations in Electromagnetism Salama Abdelhady Department of Mechanical Engineering, CIC, Cairo, Egypt. E-mail: salama_hady@cic-cairo.com Received November 10th, 2010; revised November 27th, 2010; accepted December 2nd, 2010. ABSTRACT The previously introduced US of units has raised many comments. Such comments were the claims of how to measure the electric current and magnetic flux. Other comments were concerned by violating the fundamental laws of electro- magnetism. Such violation is not the concern of the introduced system of units. But it is related to the previou s mess in the available SI system of units. Keywords: Electric Charge, Magnetic Flux, Ampere’s Law, System of Units 1. Electric Charge Electric charge was defined, according to a previously introduced entropy‐approach [1], as a form of energy or electromagnetic waves that have an electric potential, positive or negative. So; the unit of electric charge is a unit of Energy, i.e. in Joules. Hence; the current as a rate of flow of electric charge should be measured in Watt. Accordingly; the ammeter does not read such defined current but reads actually the rate of flow of electric en- ergy per Volt. This can be shown from the following well known equation that is used in electric‐ power measure- ment or calculation [2]: AV e W (1) Where A can be defined as the ammeter reading and V is the potential difference. Hence; the units of the Ammeter readings should be: A= WWatt VVolt (2) So; the universal system of units, that was previously introduced [3], may use the same ammeter as an instru- ment for measuring the current in Watt/Volt. The Am- meter does not measure actually the rate of flow of elec- tric energy as previously assumed in Coulomb/sec but it measures the flow of electric entropy associated by the electric energy [3]. 2. Magnetic Flux Magnetic Flux is defined also according to a published entropy approach and experimental work as a form of energy or electromagnetic waves that have magnetic po- tential, positive or negative [1]. So ; the magnetic flux has to be measured in the same units of energy; i.e. in Joule. According to a scientific analogy between thermal, elec- tric and magnetic energies and their common effect on an Al‐Fe thermocouple [3]; it was found that their potentials could be measured also by the Volt. Revising the tech- niques of measurement of the magnetic flux; it is found that they depend on measuring the produced electric po- tential by the influence of the measured magnetic field on a conductor that carries an electric current [4]. So; the techniques u sed do not follow a direct approach but they depend on measuring electric‐field parameters to find the correspondi n g m a gnet ic parameters. However; we can measure directly the magnetic en- ergy that performs work in attracting iron balls along an inclined plane [1]. Hence; it is possible to recalibrate the already used Gaussmeter to measure the rate of flow of magnetic flux during such attraction process. According to the proved analogy between electric and magnetic fields and the common unit of their potentials as previ- ously described; it is possible to assume the unit of measurement of the modified Gauss‐meter to be identical to the unit of Ammeter readings; i.e. in Watt/volt. So; we may introduce the following equation to measure or cal- culate the magnetic power from readings of the Gauss‐ meter by an equation that is an alogous to Equation (1): m WGH (3) Comments Concerning Measurements and Equations in Electromagnetism 678 where G is the Gauss‐meter reading and H is the mag- netic potential in Volt. Hence; th e unit of measurement in a modified Gauss‐meter for measuring the rate of flow of magnetic flux per unit magnetic potential will be, ac- cording to Equation (3), as follows: WWatt GVVolt (4) By analogy; this unit measures the rate of flow of magnetic entropy associated by the magnetic energy [3]. 3. Ampere’s Law According to Ampere’s law, the produced “E.M.F.” or voltage at the open ends of the loop is dependent of the time rate of change of the magnetic flux encircled by the loop. According to electromagnetism References [5]; the found relation is expressed as follows: =A ddB V dt dt (5) Such equation proves that the units of magnetic and electric potentials are identical. However; substitutin g the SI units of the terms in sides of Equation (5); we find the following units will result: 2 2sec sec. kg mV Amb olt Hence; this equation is incorrect from the dimensional point of view. However; Ampere’s law can be rewritten in adjustable dimensional form where the coefficient of proportional- ity between the E.M.F. or voltage at the open ends of the loop and the time rate of change of the magnetic flux encircled by the loop will be the loop area times the re- luctance of the loop; i.e. AR mdb V dt (6) According to the postulated US of units [3]; the units in both sides of Equation (6) will be equivalent: 2 2 Volt W mV Wm olt REFERENCES [1] S. Abdelhady, “A Fundamental Equation of Thermody- namics that Embraces Electrical and Magnetic Poten- tials,” Journal of Electromagnetic Analysis & Applica- tions, Vol. 2, March 2010, pp. 162-168. [2] Jewett, Jr. and R. A. Serway, “Physics for Scientists and Engineers with Modern Physics,” 7th Edition, Thomson, 2008. [3] S. Abdelhady, “An Approach to a Universal System of Units,” Jouranl Electromagnetic Analysis & Applications, Vol. 2, March 2010, pp. 162-168. [4] D. Gordon, R. Brown and J. Haben, “Methods for Meas- uring the Magnetic Field,” Magnetics, IEEE Transactions, Vol. 8, No. 1, pp. 48-51. [5] N. J. Carron, “On the Field of a Torque and the Ob- servability of the Vector Potential,” Physics Notes, Note 6, 1993. Copyright © 2010 SciRes. JEMAA |