TEORIA ELECTROMAGNETICA Y ONDAS 203058A_364
Unit 1 - Step 2 development space
Tutor:
WILMER HERNAN GUTIERREZ
Presented by:
KATHERIN LIZETH VALEGA 1.045.701.215 LEONARDO QUINTERO BEJARANO 16461422 HERNAN PORTILLO TRILLOS 13.436.865 LUIS ENRIQUE PEREZ RAVELO 1.007.126.098
Group: 243006_38
October, 2017
INTRODUCTION
In this group work, the aim is to understand and assimilate the principles that explain electromagnetic waves, to explore the theoretical applications related to e lectromagnetic waves and to investigate and develop related complementary exercises. The course of electromagnetic theory and waves, opens its doors to us to try to understand its first thematic unit. Next, the different topics to be discussed will be explained, referring to Unit 1. Electrodynamics and waves analyzing the propagation of electromagnetic waves in vacuum and in matter.
ACTIVITIES TO DEVELOP
Each student in the group has to answer the following questions using academic references to support the research:
1. How is the loss tangent used in practical situations? Give an example.
Waves, circles, and triangles are closely related. In fact, this relatedness forms the basis of trigonometry. Basic trigonometric functions are explained in this mo dule and applied to describe wave behavior. The module presents Cartesian coordinate (x, y) graphing, and shows how the sine function is used to plot a wave on a graph. Additionally, between the displacement current and the conduction current there is an angle of phase shift This relationship is called the loss tangent an d is a feature of the medium, in the conductive materials tends to be very high. An example is the synchronoscopio of a plant of generation there we can see the lags by the tangent of loss. Loss tangent or dissipation factor is the measure of the state of an insulation. It is also called dissipation factor and is the measure of the dielectric loss of a solid or liquid material Insulation gauges The tangent of loss is related to how good a conductor or insulator is a material, in the case of electromagnetic waves the main means used to transmit is air, which is affected by both weather conditions and other factors, through the use of the tangent of loss we can know that so much opposition will have the signal that we transmit in o rder to know the power that we must use for an optimal transmission.
2. What could produce losses in electromagnetics wave propagation? Explain with examples.
The factors that affect the propagation of energ y in the form of electromagnetic waves in a terrestrial link are:
Lost in Free Space: in free space the losses occur due to the distance and the
frequency of the signal
Lost by Rain: the electromagnetic wave loses energy and yields this to a raindrop
Lost by Vegetation: mainly in the microwaves, the trees near the transmitter
generate dispersion and obstruction of the signal
Lost in Transmission Lines : the transmission lines affect the power of the signal
depending on its length, the medium in which it is installed and the frequencies to be transported
Lost Miscellaneous: electronic circuits of the transmitter and receiver,
waveguides and antennas of transmission and reception
Lost by Reflection: The reflection can be understood when the radio waves cross
the different layers of the atmosphere, from the troposphere to the ionosphere and the indexes of refractivity of each of these stages are very different. These different indices may lead to total reflection, with VHF and hi gher frequencies being the most prone to this trajectory deviation.
Lost by Diffraction: Diffraction is the phenomenon that occurs when an
electromagnetic wave hits an obstacle, the earth a nd its irregularities can prevent the visibility between the transmitting and receiving antennas in certain occasions. The diffraction losses are calculated first with the normalized clearance. The attenuation occurs for the great distances. The noise consists of the electric energy, electromagnetic or of frequency of unwanted radio that can degrade and distort the quality of signals and communications of all kinds.
3. If waves are considered like means of transportation of information, what occur with the information if the wave travels in: Free space, lossless dielectrics, lossy
dielectrics or good conductors. Explain each case and support your answer in the loss tangent definition.
The propagation of electromagnetic waves by free space is often called radiofrequency propagation, or simply radio propagation. Although free space implies vacuum. The propagation by the terrestrial atmosphere is often called propagation by free space, and can almost always be considered as such.
Free space:
for the empty space, the electric field E and the magnetic field B go
in a plane transverse to the direction of propagation due to the low intrinsic impedance of the medium
Lossless dielectrics the electric field E and the magnetic field B are in phase of
time with respect to each other
Lossy dielectrics is an imperfect conductor where the wave loses power
Good conductors: in a good conductor, the information is attenuated by the
phenomenon called surface effect or depth of penetration of the medium. It is a measure of how much an electromagnetic wave can penetrate a medium.
4. Complete the following table listing applications for the given E M phenomena
EM PHENOMENA
APPLICATION
Medical diagnosis, scanner, In addition to the applications of X-rays for research X-rays
in physics, chemistry, medicine, mineralogy, metallurgy and biology, Xrays are also used in industry as a
research tool and to perform numerous test processes. Measurement instruments, Infrared radiation has many and very diverse applications as a heat source. As it is not Infrared radiation
affected by air currents, it is very suitable to be used as an external heating element. It also has military applications such as the infrared image converter allows the soldier to see in the dark. Data transmission, On land, telecommunications with microwaves are increasingly used using repeater antennas, necessary along a path or path of communication
Microwave waves
In space, satellites are used as microwave relay stations. These satellites have enormous capacity and the new generations of satellites will be even more powerful. In addition to electronic devices such as food heaters Information transmission, Several radio wave frequencies are used for television and FM and AM radio broadcasts,
Radio waves
military communications, cell phones, radio amateurs, wireless computer networks, and numerous other communications applications. Most radio waves pass freely through the
Earth's atmosphere. However, some frequencies can be reflected or absorbed by the charged particles of the ionosphere. Medical diagnosis and procedures, They are used for the processing of products and substances that require a microorganism-free environment (Gamma Rays). In areas such as physics and science in general, the irradiation processes use this particular form of Gamma rays
electromagnetic waves, that is Gamma radiation, which is also known as ionizing radiation or "ionizing energy". This term is used to describe these waves, since they cause in the material that they cross the formation of electrically charged particles, called "ions". Tomography in solid material, It´s main
Cosmic rays
uses are focused on the area of scientific research, it is currently working to be used in excavation processes
5. What can the pointing vector be used for? Transmit power measurement on antennas. The wave vector is a vector that points in the propagation direction of the wave in question and whose magnitude is the wave number. By means of the wave vector it can
be quickly seen that the plane electromagnetic waves are transverse, that is, the oscillation of the electric and magnetic field is perpendicular to the direction of propagation of the wave and perpendicular to each other.
6. What is a plane wave and a non-plane wave and where are they used? What is a magnetic and a nonmagnetic medium and where are they used?
Plane wave: In the physics of wave propagation, a plane wave (also spelled planewave) is a constant-frequency wave whose wavefronts (surfaces of constant phase) are infinite parallel planes of constant peak-to-peak amplitude normal to the phase velocity vector. It is not possible in practice to have a true plane wave; only a plane wave of infinite extent will propagate as a plane wave. However, many waves are approximately plane waves in a localized region of space. It is used for electromagnetic transmissión across a wide spectrum.
No plane wave: is that three-dimensional wave whose wave fronts for an observer at rest relative to the source and the medium in which it propagates are concentric spheres, whose centers coincide with the position of the disturbance source. A necessary condition for a wave to be spherical is that the propagation medium is homogeneous and isotropic and therefore the propagation velocity is the same in all directions. Sound waves are very nearly spherical waves when they propagate through a homogeneous and isotropic medium, such as air or water at rest. Also the light propagates in the form of spherical waves in the air, the water, or through the void. It is used for luminic transmission.
magnetic fi eld: is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any point is specified by two values, the direction and the magnitude; in such a way that it is a vector field. Specifically, the magnetic field is an axial vector, as are the mechanical moments and the rotational fields. The magnetic field is more commonly defined in terms of the
Lorentz force exerted on electric charges. Ma gnetic field can refer to two separate but closely related symbols B and H.
Magnetic permeabili ty: In physics is called magnetic permeability to the ability of a substance or medium to attract and pass through it magnetic fields, which is given by the relationship between the existing magnetic induction and the intensity of the magnetic field that appears in the interior of said material.
they used magnetic médium: A magnetic medium is a device that stores the information by means of magnetic waves. They are magnetic media hard disks, 3 1/2 "disks, audio tapes or cassettes. Magnetic media must be kept away from magnetic fields and no body with magnetic properties (such as magnets, telephones) should be brought near them, as they could cause irretrievable loss of data already stored.
Choose one of the following problems, solve it and share the solution in the forum. Perform a critical analysis on the group members’ contributions and reply this in the forum.
1. A plane wave has an electric field given by =10 medium is characterized by
=1,
−
sin(6x106t−βz)
/ If the
=25 and =2.5 / , find the skin depth,
phase and attenuation constant. Explain the meaning of these parameters in a practical application. Tangent
= = = 2 6 1 102.5 1 10− 36
= = |α|1 The general formula of constant propagation is:
= 1 Since in this case σ »ωε, we can make the following approximation:
= (1+ ) 10 When replacing we obtain:
= (1+ )43,42 = 194,16∠45 From there we can deduce that:
= = 194,16 The impedance of the wave is given by:
∠90 η = 194, 16∠45 − η = 129,4∠45 = 129,4 Hence:
H = 1η ∗ E By doing the operation and replacing the obtained data, we have to:
H = 0,015 e−j, sin 6x10t 194,16z π4a mA 2. A uniform plane wave travels in a lossless nonmagnetic medium. If the wavelength is 12cm and the velocity of propagation is 5 106 / , find:
a. The fr equency of the wave: a magnitude that measures the number of repetitions per unit time of any periodic event or phenomenon.
f = λ m/s 5 x10 f = 0,12m f = 4,16107 b. Permittivity of the médium: or permissiveness of the medium: (also called
dielectric constant) is a physical constant that describes how an electric field affects and is affected by a medium.
= √ 1 c. Phase constant: indicates the instantaneous situation in the cycle, of a magnitude
that varies cyclically, being the fraction of the period elapsed from the instant corresponding to the state taken as a reference.
= 2λ 2 = 12cm = 0,52 d. Intrinsic impedance: is a physical constant that relates the magnitudes of the
electric and magnetic fields of an electromagnetic radiation
Escriba aquí la ecuación.
4. An engineer needs to put a transmitter into lake water and into seawater. If the frequency of the signal is 15MHz what should the engineer take into account before the installation? Use the attenuation constant and penetration depth to support your answer. If the transmitter will be put one meter under the surface, what would you advise?
R// Things to keep in mind for freshwater and saltwater transmission The conductivity (s) varies with both salinity and temperature. Seawater ha s a high salt content and high conductivity ranging from 2 mhos per meter in the cold regions of the Arctic to 8 mhos per meter in the warm and highly saline waters of the Red Sea. The average conductivity of the sea is normally consid ered to be 4 mohs per meter. Which means that in a cube of 1 meter on the side of sea water has a conductivity of 4 mhos or a resistance of 0.25 ohms (it is inverse). What we call freshwater has lower conductivity and as a basis for this, we used an Adelaide water analysis sample taken in 1983. This sample was taken from an area mainly supplied by the Barossa reservoir and the analysis shows that the total salts Dissolved are approximately 300mg / liter and the conductivity of 0.0546 mhos per meter. How close that value of the average is in waters of rivers and lakes in Australia is not known, bu t it has been used as a reference. The attenuation of radio waves in water (and, in fact, in any conductive medium) increases both with the increase in conductivity and with the increase in frequency. It can be calculated with the following formula: Attenuation (alpha) in dB / meter = 0.0173 (square root of ...) f (sigma) where f = frequency in Hz. and (sigma) = conductivity in mhos / meter. The attenuation in seawater is very high and to communicate at any depth, it is necessary to use very low frequencies (10 to 30 KHz) where the attenuation is of the order of 3.5 to 5 dBs per meter. The operation in the lowest frequency of the amater band (1.8 Mhz) is out of options with 46dBs per meter.
The potential operability in fresh water is much better. Using the Adelaide water sample, the attenuation at 10Khz is 0.4 dB, increasing to 5.4 dB per meter to 1.8 Mhz. SEAWATER As mentioned before, the attenuation of radio signals in seawater is so great that communication beyond the surface is not possible unless very low frequencies are used (10 to 30 KHz). Although you could get permission to work in this band, there are other difficulties for amateur amateurs.
-The refraction of air to water has losses of the order of 60 to 70 dBs. -An antenna of enormous dimensions is required, particularly for the antennas of the surface (even at 30 Khz, the wavelength is 10Km). Normally, higher transmission powers are used to compensate for the large losses inhe rent in a smaller frequency low frequenc y antenna. -The peaks of atmospheric noise are around 16 0 dB over thermal noise (KTB) at 10 Khz, limiting the minimum level discernible in reception.
In group solve the following practical exercise
Using an excel document that contains the following information: 1. The first sheet has to contain a chart that plots the skin depth according to the following specifications. a. The user can select the initial and final frequency for the plot. b. The user can select from 4 different materials to be plotted that the group has previously defined. 2. The second sheet has to let to select a frequency and a material from the 4 that the group defined and show how the medium behave according to that parameters. R//
CONCLUSIONS
In the following work was developed and learned about the unit of electrodynamics and waves giving answers to questions to questions proposed in the guide with topics of classification and characterization of electromagnetic waves in different media, themes were identified as refractive index, constant of phase, wavelength, skin effect. The Scilab practice of some functions or mathematical bases that define the behavior of electromagnetic waves was also carried out.
BIBLIOGRAPHIC REFERENCES
Chen, W. (2005). The Electrical Engineering Han dbook. Boston: Academic Press. 513-519. Retrieved from http://bibliotecavirtual.unad.edu.co:2048/login?url=http://search.ebscohost.com/logi n.aspx?direct=true&db=nlebk&AN=117152&lang=es&site=ehostlive&ebv=EB&ppid=pp_513
Quesada-Pe rez, M., & Maroto-Centeno, J. A. (2014). From Maxwell's Equations to ́ Free and Guided Electromagnetic Waves: An Introduction for First-year Undergraduates. New York: Nova Science Pu blishers, Inc, 49-80 Retrieved from http://bibliotecavirtual.unad.edu.co:2051/login.aspx?direct=true&db=nlebk&AN=7 46851&lang=es&site=eds-live&ebv=EB&ppid=pp_49
Magnetic field. From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Magnetic_field
Permeability (electromagnetism). From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Permeability_(electromagnetism)
APA 2017 : http://normasapa.net/2017-edicion-6/
