orientation ppt emwtl .ppt
- 2. 2 What was learnt in Introduction to Electromagnetic Fields • Electromagnetics is the study of the effect of charges at rest and charges in motion. • Some special cases of electromagnetics: – Electrostatics: charges at rest – Magnetostatics: charges in steady motion (DC) – Electromagnetic waves: waves excited by charges in time-varying motion
- 3. What happens when electric and magnetic fields change? A changing magnetic field creates a changing electric field.
- 4. What happens when electric and magnetic fields change? A changing magnetic field creates a changing electric field Faraday’s law. One example of this is a transformer which transfers electric energy from one circuit to another circuit.
- 5. What happens when electric and magnetic fields change? A changing magnetic field creates a changing electric field. One example of this is a transformer which transfers electric energy from one circuit to another circuit. In the main coil changing electric current produces a changing magnetic field Which then creates a changing electric field in another coil producing an electric current The reverse is also true.
- 6. Electromagnetic Waves… Do not need matter to transfer energy.
- 7. Electromagnetic Waves… Do not need matter to transfer energy. Are made by vibrating electric charges and can travel through space by transferring energy between vibrating electric and magnetic fields.
- 8. Making Electromagnetic Waves When an electric charge vibrates, the electric field around it changes creating a changing magnetic field.
- 9. Making Electromagnetic Waves The magnetic and electric fields create each other again and again. Maxwell theoretically showed from his equations that an electromagnetic field can detach itself from sources &propagate through space as a field package, known as electromagnetic wave.
- 10. Making Electromagnetic Waves An EM wave travels in all directions. The figure only shows a wave traveling in one direction.
- 11. Making Electromagnetic Waves The electric and magnetic fields vibrate at right angles to the direction the wave travels so it is a transverse wave.
- 12. What is the speed of EM waves? Material Speed (km/s) Vacuum 300,000 Air <300,000 Water 226,000 Glass 200,000 Diamond 124,000
- 13. What is the wavelength & frequency of an EM wave? Wavelength= distance from crest to crest.
- 14. What is the wavelength & frequency of an EM wave? Wavelength= distance from crest to crest. Frequency= number of wavelengths that pass a given point in 1 s.
- 15. What is the wavelength & frequency of an EM wave? Wavelength= distance from crest to crest. Frequency= number of wavelengths that pass a given point in 1 s. As frequency increases, wavelength becomes….
- 16. What is the wavelength & frequency of an EM wave? Wavelength= distance from crest to crest. Frequency= number of wavelengths that pass a given point in 1 s. As frequency increases, wavelength becomes smaller.
- 17. The whole range of EM wave… Frequencies is called the electromagnetic spectrum.
- 18. The whole range of EM wave… Frequencies is called the electromagnetic spectrum. Different parts interact with matter in different ways.
- 19. The whole range of EM wave… Frequencies is called the electromagnetic spectrum. Different parts interact with matter in different ways. The ones humans can see are called visible light, a small part of the whole spectrum.
- 20. As wavelength decreases, frequency increases…
- 21. • Natural sources of electromagnetic fields Electromagnetic fields are present everywhere in our environment but are invisible to the human eye. Electric fields are produced by the local build-up of electric charges in the atmosphere associated with thunderstorms. Lightning is a sudden electrostatic discharge during an electric storm between electrically charged cloud and another cloud (CC lightning), or between a cloud and the ground (CG lightning). The charged regions within the atmosphere temporarily equalize themselves through a lightning flash, commonly referred to as a strike if it hits an object on the ground. The earth's magnetic field causes a compass needle to orient in a North-South direction and is used for navigation.
- 22. • Human-made sources of electromagnetic fields Besides natural sources the electromagnetic spectrum also includes fields generated by human-made sources: X-rays are employed to diagnose a broken limb after a sport accident. The electricity that comes out of every power socket has associated low frequency electromagnetic fields. And various kinds of higher frequency radiowaves are used to transmit information – whether via TV antennas, radio stations or mobile phone base stations.
- 23. Devices detect other frequencies: Antennae of a radio detects radio waves.
- 24. Devices detect other frequencies: Antenna of a radio detects radio waves. Radio waves are low frequency EM waves with wavelengths longer than 1mm.
- 25. Devices detect other frequencies: Antennae of a radio detects radio waves. Radio waves are low frequency EM waves with wavelengths longer than 1mm. These waves must be turned into sound waves by a radio before you can hear them.
- 26. What are microwaves? Microwaves are radio waves with wavelengths less than 30 cm and higher frequency & shorter wavelength. Cell phones and satellites use microwaves between 1 cm & 20 cm for communication. In microwave ovens, a vibrating electric field causes water molecules to rotate billions of times per second causing friction, creating TE which heats the food.
- 27. How does radar work? Radio Detecting And Ranging or radar is used to find position and speed of objects by bouncing radio waves off the object.
- 28. What is magnetic resonance imaging? MRI scanners use strong magnetic fields and radio waves to form images of the body.
- 29. Infrared Waves EM with wavelengths between 1mm & 750 billionths of a meter. Used daily in remote controls, to read CD- ROMs Every objects gives off infrared waves; hotter objects give off more than cooler ones. Satellites can identify types of plants growing in a region with infrared detectors
- 30. Visible Light Range of EM humans can see from 750 billionths to 400 billionths of a meter. You see different wavelengths as colors. Blue has shortest Red is the longest Light looks white if all colors are present
- 31. Ultraviolet Waves EM waves with wavelengths from about 400 billionths to 10 billionths of a meter. Have enough energy to enter skin cells Longer wavelengths – UVA Shorter wavelengths – UVB rays Both can cause skin cancer
- 32. Can UV radiation be useful? Helps body make vitamin D for healthy bones and teeth Used to sterilize medical supplies & equip Detectives use fluorescent powder (absorbs UV & glows) to find fingerprints
- 34. X Rays and Gamma Rays EM waves with shortest wavelength & highest frequency High Energy- go through skin & muscle High level exposure causes cancer
- 35. X Rays and Gamma Rays EM with wavelengths shorter than 10 trillionths of a meter. Highest energy, can travel through several centimeters of lead. Both can be used in radiation therapy to kill diseased cells. The composite image shows the all sky gamma ray background.
- 36. Radio Transmission Radio stations change sound to EM waves & then your radio receiver changes the EM waves back to sound waves again.
- 37. Television The basic idea of television is "radio with pictures". In other words, where radio transmits a sound signal (the information being broadcast) through the air, television sends a picture signal as well. You probably know that these signals are carried by radio waves, invisible patterns of electricity and magnetism that race through the air at the speed of light (300,000 km or 186,000 miles per second).
- 38. What is a cathode-ray tube? Many TVs and computer monitors display images on a CRT, a sealed vacuum tube in which beams of electrons are produced. CRT working involves understanding charge motion in electric and magnetic fields. Basically a stream of electrons is accelerated by an electric field &then deflected by a magnetic field, to trace a point on the front surface of the monitor & point by point a full image.
- 39. Telephones Sound waves microphone electric signal radio waves transmitted to and from microwave tower receiver electric signal speaker sound wave
- 40. Communications Satellites Thousands of satellites orbit Earth. A radio or TV station sends microwave signals to the satellite which amplifies the signal and sends it back to a different place on Earth. Satellite uses dif freq to send & receive.
- 41. Global Positioning System GPS is a system of 24 satellites, ground monitoring stations and portable receivers that determine your exact location on Earth. GPS receiver measures the time it takes for radio waves to travel from 4 different satellites to the receiver. The system is owned and operated by the US Dept of Defense, but the microwaves can be used by anyone.
- 42. Applications RF communication Microwave Engineering Antennas Electrical Machines Satellite Communication Atomic and nuclear research Radar Technology Remote sensing EMI EMC Quantum Electronics VLSI
- 43. COURSE OBJECTIVES: Students will read and analyze different laws and theorems to find electric field due to different charge distributions. Student will read and analyze the effects of static magnetic fields due to different current distributions. Students will understand the Maxwell equations, the concepts of wave theory its propagation through various media. Students will learn the concepts like polarization, reflection, refraction and pointing vector. Students will get an exposure to the properties of transmission line, electromagnetic wave propagation in transmission line geometries.
- 44. COURSE OUTCOMES: Have the ability to use different laws and theorems to find electric field due to different charge distributions Have the ability to understand the effects of static magnetic fields due to different current distributions Grasp the importance of the Maxwell equations, the concepts of wave theory its propagation through various media Have the ability to understand the concepts like polarization, reflection, refraction and pointing vector Have the ability to understand the properties of transmission lines, electromagnetic wave propagation in transmission line geometries.
- 45. COURSE PRE-REQUISITES: 1. Vector calculus 2. Co-ordinate systems
- 46. SYLLABUS WITH TEXT BOOKS & REFERENCE BOOKS. SYLLABUS UNIT I ELECTROSTATICS: Introduction to 3-D orthogonal co ordinate transformations and vector calculus , Coulomb’s Law and Electric Field Intensity, Electric Fields due to continuous Charge Distributions, Electric Flux Density, Gauss Law and Applications, Electric Potential, Relations Between E and V, Energy Density, Convection and Conduction Currents, Dielectric Constant, Isotropic and Homogeneous Dielectrics, Continuity Equation, Relaxation Time, Poisson’s and Laplace’s Equations, Capacitances and energy density. Related problems. UNIT II MAGNETO STATICS: Introduction, Biot-Savart Law, Ampere’s Circuital Law and Applications, Magnetic Flux Density, Magnetic Scalar and Vector Potentials, Forces due to Magnetic Fields, Ampere’s Force Law, inductance and magnetic energy density. Related problems.
- 47. UNIT III MAXWELL’S EQUATIONS : Introduction, Faraday’s Law, Transformer and motional emf, inconsistency of Ampere’s Law and Displacement Current Density, Maxwell’s equations in differential, Integral form and word statements. Boundary conditions: Dielectric-Dielectric and Dielectric-Conductor Interfaces. Related problems. UNIT IV ELECTROMAGNETIC WAVE EQUATIONS: Introduction, Applications of EM waves, Wave equations for conducting, dielectric and lossless media, Uniform Plane Wave (UPW) and general solution of UPW. Relations between E & H in UPW. Characterization of conductors and dielectrics, wave propagation in good conductors and good dielectrics, skin depth, polarization. Related problems. UNIT V ELECTROMAGNETIC WAVE CHARACTERISTICS : Introduction Normal and Oblique incidence of UPW on perfect conductor and perfect dielectrics, Brewster angle, critical angle and total internal reflection, surface impedance. Poynting Vector and Poynting theorem – applications, Related problems.
- 48. UNIT VI TRANSMISSION LINES: Types, Applications, equivalent circuit of two wire parallel transmission lines, Primary constants, Line Equations, Secondary Constants, Expressions for Characteristic Impedance, Propagation Constant, Phase and Group Velocities, Infinite Line Concepts, Loss less and Low Loss Characterization, Distortion – Condition for Distortion less and Minimum Attenuation, Input Impedance Relations, SC and OC Lines, Reflection Coefficient, VSWR. UHF Lines as Circuit Elements; λ/4, λ /2, λ/8 Lines . Smith Chart – Construction and Applications, Single stub. Related problems.
- 49. TEXT BOOKS: 1. Electromagnetic Field Theory And Transmission Lines – GSN Raju, Pearson Education 3rd edition 2009. 2. Elements of Electromagnetics – Matthew N.O. Sadiku, Oxford Univ. Press, 4th ed., 2007 REFERENCES: 1. Engineering Electromagnetics – Nathan Ida, Springer (India) Pvt. Ltd., New Delhi, 2nd ed., 2005. 2. Electromagnetic Waves and Radiating Systems – E.C. Jordan and K.G. Balmain, PHI, 2nd Edition, 2000. 3. Engineering Electromagnetics by William H. Hayt Jr. and John A Buck, TMH, 7th Edition.
- 50. SYLLABUS COVERED IN GATE ELECTROMAGNETICS Electrostatics; Maxwell’s equations: differential and integral forms and their interpretation, boundary conditions, wave equation, Poynting vector; Plane waves and properties: reflection and refraction, polarization, phase and group velocity, propagation through various media, skin depth; Transmission lines: equations, characteristic impedance, impedance matching, impedance transformation, Smith chart SYLLABUS COVERED IN IES ELECTROMAGNETIC THEORY Analysis of electrostatic and magneto static fields; Laplace’s and Poisson’s equations; Boundary value problems and their solutions; Maxwell’s equations; application to wave propagation in bounded and unbounded media; Transmission lines : basic theory, standing waves, matching applications.