Note: Links to 3 videos with simulation of radiation included. How does an antenna radiate? Every stationary charge such as an electron and a proton has an electric field surrounding it. When the charge moves, it produces a magnetic field. When the charge is accelerated or several charges accelerate, an electromagnetic wave is radiated. Radio waves and light are electromagnetic waves comprising electric and magnetic field pulsations or variations in their strength at each point in the space. They are produced by accelerated electric charge like the electrons of atoms in antenna rods. The radiated fields constitute a wave travelling through space. The fields don't travel, the wave does. This is best visualised by a rope, one end of which is fixed to a wall and the loose end held some distance away. The loose end when moved up and down creates a wave travelling. Notice how the molecules of the rope near the wall have not travelled to the loose end. The snake-like shape in the form of a sinewave and travelling movement you see is the overall effect of the up and down movement of the molecules of the rope. The same happens with the strength of electric and magnetic fields of radio waves and light. There are no sinewaves in space! It is the strength of the electric field say, which we plot of a radio wave which has a pattern of a sinewave. The radiated fields produce a transverse wave and the space size of the comment section is not sufficient to provide an explanation of how a transverse wave is produced by an accelerated or decelerated charge. Video 1 Field lines for a particle moving with high speed www1.astrophysik.uni-kiel.de/~hhaertel/Videos/large-velocity.mp4 Video 2 Field lines for an oscillating particle in 2D www1.astrophysik.uni-kiel.de/~hhaertel/Videos/oscillation-2d.mp4 Video 3 Field lines for an oscillating particle in 3D www1.astrophysik.uni-kiel.de/~hhaertel/Videos/fast-osc-particle.mp4 To learn more see "Electric and Magnetic Interactions" by Chabay and Sherwood www.matterandinteractions.org or Fundamentals of electric theory and circuits by Sridhar Chitta www.wileyindia.com/fundamentals-of-electric-theory-and-circuits.html The book by Sridhar Chitta, begins with the fundamentals of charge, electric field, surface charge, current, voltage, simple circuit, parallel circuit, capacitors and capacitive reactance, inductors, inductive reactance, induced fields and transmission line effects, antennas and wave propagation, and waveguides. The topics described in the book, make a distinct unified approach to electrostatics and circuits lending precision and clarity to the topics which is not found in most text books. The book comes alongwith a CD with animated power point presentations for all chapters and voltage regulator, RC phase shift oscillators and differential amplifiers included additionally. There is a "look inside" feature in the amazon.com webpage of the book "Fundamentals of electric theory and circuits" by Sridhar Chitta with a few pages of Chapter 1 which may be viewed and also which you may swipe left or press < icon to view the foreword, preface and Table of Contents. For a nice video about antennas and radiation visit czcams.com/video/-F7KYLO4Bkg/video.html For a lecture by Prof Ruth Chabay on radiation and reradiation, watch from the 59.0 minute czcams.com/video/VKqCI9pU3QI/video.html
The electric and magnetic fields explain the near field. The far field (radiation into space) is a result of special relativity's effect on accelerating charges. The emitted photons slow the electrons (or possibly positive charges, but electrons in nearly all antennas) which causes the radiation resistance.
I guess another lie we were told, that to have current of any sort in a wire it needs to make a loop and come back to the source. Now you can have current in an open circuit. I was aware that with enough high voltage you can get spark jump in a spark plug, but not electron jump. And now this: You can have photons come out of wires and the catch is simply to bend them exactly at 90 degrees as a result of electron current, but open to space and not loop back as one wire.
Electrostatics and circuits belong to one science not two. For a unified approach to learning Current and the process of conduction watch these two videos i. czcams.com/video/REsWdd76qxc/video.html and ii. czcams.com/video/8BQM_xw2Rfo/video.html Also, in the textbooks referred in the last frame of video i you will find descriptions of the operation of resistors, capacitors and inductors using this approach which makes it easier to understand. There are also a chapter in the textbook references 'Fundamentals of electric theory and circuits' which explains the operation of antennas and waveguides using the unified approach.
Thank you for your persuasive explanation. I need someone to tell me which text book the teacher is using please( full name). I'm student and it's useful for me.
Exactly what I was going to say. The induced E fields in the "Side View, Later" section on the right side of the slide are incorrect. They should be opposite from the left side view.
Thank you for your explanation it is very clear and to the point. I have a question, How can I know the distance the radiated waves travel from the antenna? any general formula?
Note: Links to 3 videos with simulation of radiation included.
How does an antenna radiate?
Every stationary charge such as an electron and a proton has an electric field surrounding it. When the charge moves, it produces a magnetic field. When the charge is accelerated or several charges accelerate, an electromagnetic wave is radiated.
Radio waves and light are electromagnetic waves comprising electric and magnetic field pulsations or variations in their strength at each point in the space.
They are produced by accelerated electric charge like the electrons of atoms in antenna rods. The radiated fields constitute a wave travelling through space.
The fields don't travel, the wave does.
This is best visualised by a rope, one end of which is fixed to a wall and the loose end held some distance away.
The loose end when moved up and down creates a wave travelling.
Notice how the molecules of the rope near the wall have not travelled to the loose end.
The snake-like shape in the form of a sinewave and travelling movement you see is the overall effect of the up and down movement of the molecules of the rope.
The same happens with the strength of electric and magnetic fields of radio waves and light.
There are no sinewaves in space! It is the strength of the electric field say, which we plot of a radio wave which has a pattern of a sinewave.
The radiated fields produce a transverse wave and the space size of the comment section is not sufficient to provide an explanation of how a transverse wave is produced by an accelerated or decelerated charge.
Video 1 Field lines for a particle moving with high speed
www1.astrophysik.uni-kiel.de/~hhaertel/Videos/large-velocity.mp4
Video 2 Field lines for an oscillating particle in 2D
www1.astrophysik.uni-kiel.de/~hhaertel/Videos/oscillation-2d.mp4
Video 3 Field lines for an oscillating particle in 3D
www1.astrophysik.uni-kiel.de/~hhaertel/Videos/fast-osc-particle.mp4
To learn more see "Electric and Magnetic Interactions" by Chabay and Sherwood
www.matterandinteractions.org
or
Fundamentals of electric theory and circuits by Sridhar Chitta
www.wileyindia.com/fundamentals-of-electric-theory-and-circuits.html
The book by Sridhar Chitta, begins with the fundamentals of charge, electric field, surface charge, current, voltage, simple circuit, parallel circuit, capacitors and capacitive reactance, inductors, inductive reactance, induced fields and transmission line effects, antennas and wave propagation, and waveguides. The topics described in the book, make a distinct unified approach to electrostatics and circuits lending precision and clarity to the topics which is not found in most text books.
The book comes alongwith a CD with animated power point presentations for all chapters and voltage regulator, RC phase shift oscillators and differential amplifiers included additionally.
There is a "look inside" feature in the amazon.com webpage of the book "Fundamentals of electric theory and circuits" by Sridhar Chitta with a few pages of Chapter 1 which may be viewed and also which you may swipe left or press < icon to view the foreword, preface and Table of Contents.
For a nice video about antennas and radiation visit czcams.com/video/-F7KYLO4Bkg/video.html
For a lecture by Prof Ruth Chabay on radiation and reradiation, watch from the 59.0 minute
czcams.com/video/VKqCI9pU3QI/video.html
Brilliant - very clear diagrams, a good pace and nice intuitive descriptions. Thank you.
Very easy explanation...
The electric and magnetic fields explain the near field. The far field (radiation into space) is a result of special relativity's effect on accelerating charges. The emitted photons slow the electrons (or possibly positive charges, but electrons in nearly all antennas) which causes the radiation resistance.
I guess another lie we were told, that to have current of any sort in a wire it needs to make a loop and come back to the source. Now you can have current in an open circuit. I was aware that with enough high voltage you can get spark jump in a spark plug, but not electron jump. And now this: You can have photons come out of wires and the catch is simply to bend them exactly at 90 degrees as a result of electron current, but open to space and not loop back as one wire.
The circuit isn't open. The separated wires form a capacitor. The capacitor "passes" the high-frequency AC...
Great video thanks!
How come you exclude Maxwells Displacement Current when describing a working antenna?
Electrostatics and circuits belong to one science not two. For a unified approach to learning Current and the process of conduction watch these two videos i. czcams.com/video/REsWdd76qxc/video.html and
ii. czcams.com/video/8BQM_xw2Rfo/video.html
Also, in the textbooks referred in the last frame of video i you will find descriptions of the operation of resistors, capacitors and inductors using this approach which makes it easier to understand.
There are also a chapter in the textbook references 'Fundamentals of electric theory and circuits' which explains the operation of antennas and waveguides using the unified approach.
Tnx for explaining
As the radiation is happening and at the same time the reflection coefficient is 1, with this whole energy will be reflected?
Thank you for your persuasive explanation.
I need someone to tell me which text book the teacher is using please( full name). I'm student and it's useful for me.
Perhaps you already graduated, but for future readers: the textbook is Fundamentals of Applied Electromagnetics, by F. Ulaby.
How do I make a antenna to get military frequencies or police frequencies
we are not in the 80's :D
From 5:26 the blue E fields point in the same direction even though the current and magnetic fields have changed direction. That cant be right.
Exactly what I was going to say. The induced E fields in the "Side View, Later" section on the right side of the slide are incorrect. They should be opposite from the left side view.
what is the name of your book
we want to download it pls
So can someone please explain to me how current can flow through a dipole antenna when the circuit is not closed?
it's as simple as capacitor charging and discharging
@@beharajagadeesh9001 how can it charge and discharge when the current has nowhere to flow
Especially with low voltages
Charge will accumulate on the antenna because of applied voltage (according to signal) and discharges accordingly applied signal
@@beharajagadeesh9001 what about rc antenna with a single long wire
So you bent just a bit of it and got an antenna. Great! What if you bend much more of it? What happens then?
You would tune the antenna to a different wavelength.
Antenna Design and RF Layout Rules ( Part I )
@t
Thank you for your explanation it is very clear and to the point. I have a question, How can I know the distance the radiated waves travel from the antenna? any general formula?
Kittu
THIS IS NOT WHAT I CAME TO TALK TO YOU ABOUT TODAY 6:01
Essentially no offence to the professor, but does he do this essentially on purpose?😅😅