What is Excitation: Definition and 142 Discussions

An electric generator or electric motor consists of a rotor spinning in a magnetic field. The magnetic field may be produced by permanent magnets or by field coils. In the case of a machine with field coils, a current must flow in the coils to generate the field, otherwise no power is transferred to or from the rotor. The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current. Hybrid topologies exist, which incorporate both permanent magnets and field coils in the same configuration. The flexible excitation of a rotating electrical machine is employed by either brushless excitation techniques or by the injection of current by carbon brushes (static excitation).

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  1. O

    Excitation by photons smaller than energy interval

    Hi people, Time-dependent perturbation theory allows for transitions to excited states, through a sinusoidal perturbation whose frequency is smaller than the energy difference between the states. (That is, P_{a \rightarrow b}=\frac{sin^{2}[(\omega_{0}-\omega)t/2]}{(\omega_{0}-\omega)^2}...
  2. S

    Base Excitation Problem: Testing Fixture Vibration Levels in Ansys

    Hello all, This is my 1st post on this forum. I am struggling with one problem. I have done actual testing of a fixture on vibration table. where I have checked g level at various points of fixture with the help of accelerometers. I had vibration table excited from 0 - 80 Hz, sine wave, 1g...
  3. A

    Electronic Excitation: Absorbing and Re-emitting Photons

    What's happen when a molecule or an atom is already in an excited electronic state and is hit from another photon? Example 1: my molecule absorbs a VIS photon (there's a time in which the molecule is an upper electronic state before the re-emission or etc. etc. process) what happen if another...
  4. O

    How Can I Construct an Excitation Circuit for a 3-Wire RTD?

    Hi everyone, Im looking to measure the resistance of a 3-wire RTD using a basic data acquisition system and LabVIEW. My DAQ "box" doesn't have any internal excitation sources, and I realize one is necessary to measure resistance across the RTD element. I'm unsure as to how to construct am...
  5. H

    How would you classify this Excitation Force?

    Hi guys, I will really appreciate it if you respond to this my question. Actually I am working on a linear generator that can be use on land to generate electricity from the movement of vehicles. The system consists of a magnet that is connected to a spring as shown in the picture. The...
  6. V

    Excitation of optical branch phonons

    As I studied, the optical branch of a crystal is called so because it can be excited with e.m. fields but I wondered whether it is possible to excite the optical branch also with chargeless particles like neutrons or the charge/action-on-charge is necessary for the process? And if so, why? I...
  7. J

    [Novice] Feynman Diagram for Electron Excitation

    I have drawn up what I believe happens during electron excitation in an atom. However, it looks very... wrong somehow. My diagram shows an elestron moving in time but not space until it is hit by a photon, after which it disappears and instantly reappears at a higher energy level. After some...
  8. G

    Excitation levels (gamma ray spectrum) of a single proton nucleus

    where can I get information about the excitation levels (gamma ray spectrum) of a single proton nucleus?
  9. T

    Understanding Anode Break Excitation in Neuroscience: A Comprehensive Guide

    Hey, Can someone point me in the direction (or just explain to me!) the idea of Anode Break excitation in neuroscience ? Thanks
  10. T

    Engineering Exam question: synchronous motor excitation

    Here is a multiple choice question i was completely stumped on, and still can't find the right answer for in my textbooks... Name 2 forms of excitation with respect to synchronous motors: a) under and over excitation b) dc & ac variation c) dc excitation and load variation d) armature and...
  11. D

    How Does Excitation on a Rotor Affect Reactive Power Output?

    I know as a fact that excitation (amount of current on the generator rotor) determines the amount of reactive power output from the generator. But why? How does it turning the excitation up or down influence the reactive power output? Thanks.
  12. T

    How Do Phonon-Related IR-Absorption Processes Differ Between Ge and GaAs?

    Homework Statement Discuss the difference between phonon related ir-absorption processes in Ge and GaAs. For instance, excitation of TO-phonon by photon.Homework Equations The Attempt at a Solution I really don't know how I should phrase my answer. Thoughts that I have include: Since GaAs is...
  13. D

    Pendulum driven by combination of horizontal and vertical excitation

    Hello there, Could some one help me to find equations of motions of this problem attached to this message? thanks a lot Niko
  14. H

    Atom Excitation: Absorption Peaks or short wavelengths?

    I just have a quick question. Which way of Atom Excitation is more efficient? Photon Energy which matches the absorption peak(s)? Or Photon energy of a Shoter wavelength than the absorbtion Peak?
  15. H

    Question on excitation energy?

    Just wanted to ask a simple question to clarify my thinking. The Ionization Energy of an atom is said to be the minimum energy required to bring the electron to it's next higher orbit. Looking at the Oxygen atom's first ionization energy of 13.6eV. Does this mean that any energy level...
  16. V

    Absorption coefficient per unit path length determined for excitation

    How is the absorption coefficient per unit path length determined for excitation sites in a host crystal with an excitation site density of N and a bandgap of the excitation site equal to the photon energy? What I am trying to determine is how many photons will be absorbed for a given length.
  17. P

    Measuring Vibration Excitation Radius & Alpha Parametar

    When we have vibration excitation then the radius of nucleus is define like: R=R_0[1+\sum^{\infty}_{\lambda=0}\sum^{\lambda}_{\mu=-\lambda}\alpha_{\lambda\mu}Y^{\lambda}_{\mu}(\theta,\phi)] where \alpha_{\lambda,\mu}=\alpha_{\lambda,-\mu} and \alpha_{\lambda,\mu}=\alpha_{\lambda,\mu}(t)...
  18. hagopbul

    Nuclear Excitation: Measurement & Laws

    I have this question about the nuclei can it excited like we do with the electrons of atoms Or in other word for example if the nuclei in the stat that is n=1, E=E(1) Can we excite it to n=2 ,E=(2) ….. and how what we use for this how we can measure it ...i think it will be a...
  19. M

    Transformer: Excitation Frequency and Turns Ratio

    Another transformer question: if I have an oil-filled transformer coil and I calculate the turns ratio with voltage in / voltage out at 60 Hz, why, when I increase the frequency to 23 kHz would the turns ratio appear to change? Is it because of the inductance of the primary coil? My boss'...
  20. D

    Exploring the Excitation Dynamics of He-Ne Lasers

    hallo all, I was wondering the following thing: when using a He-Ne laser, you pump some energy in the system to get the He excited, but why only the He atoms? If you pump energy in the systems, wouldn't the Ne atoms get excited too ? (and I am not speaking about them getting excites because...
  21. G

    Basic question on electron, ion and photon excitation

    hello, everyone, I am not in this filed. So I get a simple question. Besides field emission and thermionic emission, is there any other means to excite the eletron and get electron beam. Could anyone tell me some basic similar ways to excite the ion and photon? Thanks.
  22. L

    Concept Question about Excitation of Atoms

    Let's say, for ease of reference, an electron strikes a mercury atom with just enough energy such that this mercury atom is excited to another energy level. What would happen if a photon struck this atom with the same amount of energy? I remember encourtering a True/False problem like this in a...
  23. A

    Solving Phonon Excitation in Diatomic Lattices

    Homework Statement Ok, I need to show that in an acoustic mode of vibration in a diatomic lattice, for small k, \omega \propto k, and find the constant of proportionality. Homework Equations A_1\left(\omega^2M-\frac{2T}{a}\right)+A_2\left(\frac{2T}{a}cos(ka)\right)=0 , and...
  24. N

    Excitation of an electron by a photon

    Hi, I had a question regarding excitation. If a photon is absorbed by an electron, and some of the energy is gained by the electron, which then moves to a higher energy level, what happens to the rest of the photon's energy - is a photon of lower energy, corresponding to the difference in...
  25. G

    Excitation levels and Nucleus Size

    How would you use excitation levels (or the lowest excitation level) to find the radius of a nucleus? And how would it differ to using the r=r0A^(1/3) formula?
  26. S

    What Distinguishes an Excitation Spectrum from an Absorption Spectrum?

    What's the difference between an excitation spectrum and an absorption spectrum for the same molecule? Are the words interchangeable, or are they completely different processes? In Sharma, A. and Schulman, S. G. (1999). Introduction to Fluorescence Spectroscopy. Wiley interscience, it says...
  27. S

    Excitation and Polarization of Light

    Let's say I have a molecule with a carbonyl (C=O) group on it. Let's assume that the carbonyl group is positioned in a such a way that when we look at it the carbon is below the oxygen (so it's vertical). Therefore, it is stretching up and down. What would happen if p-polarized light (E...
  28. M

    How Can I Control Synchronous Motor Excitation?

    Im a electrical engineering student. I am now trying to understand the operation of synchronous motor. I need helps from electrical professionals out there about the excitation system of the motor. can someone give me a circuit diagram of the exciter? any advice on the methods of...
  29. P

    How are the excitation energies of helium determined experimentally?

    What is the excitation energy of the He atom? I imagine this is also the energy of the photon released by the electron as it deexcites from the p orbital to the s orbital. I guess this would be different to ionisation energy as that refers to taking the electron away completely from the atom...
  30. P

    Understanding Atom Excitation in He-Ne Lasers

    hello every one The thing I can't understand is 1) In He-Ne laser the He atoms in the excited state interact with the Ne atoms in the ground state how it is possible? 2) In all the textbooks they wrote that "atoms exite". Wil the atoms exite or the electrons? because to my knowledge atom...
  31. J

    Effect of Damping on Steady State Vibration:Harmonic Excitation

    Considering the response of a single degree of freedom system to harmonic excitation with viscous damping , following conclusions can be drawn: Now, The response of a single degree of freedom system to harmonic excitation can be split into: a) Steady Sate response (or vibration) which...
  32. J

    Response of a Single Degree of Freedom System to HArmonic Excitation

    I have been reading "Response of a Single Degree of Freedom System to Undamped system" and have been referring the book on Dynamics of Structures by Anil K. Chopra.I have got the following questions: 1) One , basic question I have is that the author says that an example of a harmonic...
  33. M

    Q:What is the analogue of the excitation vector in the case of mass density?

    Mass density is a 3-form, just like electric charge density. Hence it's exterior derivative is 0. This implies that there is a 2-form whose exterior derivative is the density 3-form. If this density is the electric charge density, then the name of this 2-form is "excitation" (D). But what is the...
  34. J

    Is Precision of Excitation Voltage Important for Load Cell Accuracy?

    Hello, I'm trying to decide how I will provide excitation voltage to the wheatstone bridge of a load cell. The output of the load cell will be amplified by an LT1167 In-Amp. How concerned should I be about the precision/accuracy of the excitation voltage? Since the In-Amp will reject common...
  35. K

    Separation of Isotopes by Laser Excitation

    Is this for real? http://www.smh.com.au/news/national/laser-enrichment-could-cut-cost-of-nuclear-power/2006/05/26/1148524888448.html
  36. A

    Calculate K Excitation Voltage & Wavelength of Copper

    for these problem: 1.calculate the K excitation voltage of copper. 2. calculate the wavelength of the Cu K(alpha 1) line. my problem: with that limited amount of information, how are you supposed to calculate it?
  37. G

    Counting Possible Configurations for n Bosons Restricted to kth Excitation

    A typical stat mech. question is the following: If I have 5 bosons and energy E to divide among the bosons, what is the total number of possible configurations? I can't remember this answer, so if someone reading this can post it that would be appreciated. Now, I want to ask a slightly...
  38. R

    Photon Absorption & Excitation of Electrons in Atoms

    When a photon hits an atom it gets absorbed and an electron moves one or more shells up depending on the energy of the photon. When a bigger, many-electron atom gets hit by a photon, can the electrons in the lower shells get excited? I mean when they move up they have to remove the electrons in...
  39. W

    Hydrogen excitation (griffiths 9.1)

    I'm trying to solve problem 9.1 from griffiths book on quantum mechanics. I've written down the hydrogen wavefunctions for all combinations allowed of n, l and m. Now according to griffiths (and my memory) only one excitation is actually allowed between n=1 and n=2. This would minimize the...
  40. B

    Carbon 12 Excitation Levels Up to 22.6 MeV w/ JPI Descriptions

    can anyone please provide me all the excited levels of Carbon 12 upto 22.6 MeV at least with jpi descriptions? Thanks in advance.
  41. J

    Calculation of Excitation potentialfrom I-V curve

    From a current v voltage graph, how does one calculate the excitation potential? I thought it was calculate the difference between peaks, take an average and this gives you the excitation potential? Is this right or is there a different way to calculate it? James
  42. H

    Excitation, ionization, TEMPERATURE?

    excitation, ionization, TEMPERATURE?? When atomic electrons are excited or ionized, do they contribute to temparature rise?? If yes, what energy of the electron is significant in this case??
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