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. R

    Difference between phonon and electron excitation

    Homework Statement Homework Equations Debye approximation. The Attempt at a Solution For the first question (a) he has taken the lowest energy transition to be 0.2eV. (3eV-2.8eV with k=0) For the second question (b) he has taken the lowest energy transition to be at k=1. (it works out as...
  2. A

    Alternator Vibration During Excitation

    Hi guys, I'm new to this forum and this would be my first post :-) Hope you guys can guide me on what to do on this alternator that's having problem with vibration. I'm running out of ideas now on what to do with this alternator. The alternator was sent to our workshop by the client for...
  3. R

    Stress at crack tip of a 2D cantilever beam under sinusoidal excitation

    I need some information urgently. I am working on crack of a 2-D cantilever beam. One side of the beam is fixed. I am applying a sinusoidal time varying load on other end in Y-direction.Beam length and width are 100cm and 10cm respectively. crack is 05 cm in y-direction. I have attached data and...
  4. gracy

    Understanding Hydrogen Gas Excitation & Absorption

    If the hydrogen gas is supposed to emit photons when the electrons undergo excitation, then why did the gas absorb energy earlier and got the electrons excited?
  5. D

    ODE with base excitation caused by a half sine wave

    Homework Statement The suspension system of a car traveling on a bumpy road has a stiffness of ##k = 5\times 10^6## N/m and the effective mass of the car on the suspension is ##m = 750## kg. The road bumps can be considered to be periodic half sine waves with period ##\tau##. Determine the...
  6. S

    Does quality factor of a resonator depend on the excitation signal?

    Hi I am curious to know if quality factor of a resonator depends on the excitation signal or if it stay the same irrespective of the signal applied? Thanks
  7. V

    Excitation to optically forbidden state

    Can somebody please explain how electron impact can cause optically forbidden transitions in atoms and molecules ?
  8. H

    Does electron excitation for atoms above hydrogen happen at the valenc

    Does electron excitation for atoms above hydrogen happen at the valence before the core electrons first? I know that for a gamma ray it is due to the excitation within the nucleus, but what about for normal emission spectra. Do we just shine a bunch of different energy onto the atom and...
  9. T

    Atomic excitation via photon absorption

    Hi guys! I have come across a problem I can't seem to wrap my head around. I've learned that E.M. radiation can be propagated by discrete packets of energy , photons. Is the energy of each photon discrete, or can it have a continuous range of energies depending on its frequency? I would be...
  10. R

    Hydrogen excitation, ionisation and photon absorption

    I need help with something that i seemed to remember was fairly easy, but just can't seem to find the simple formula for: I have an amount of hydrogen atoms at a temperature of 10000 Kelvin. What percentage of them are ionised and what percentage of them are in the n=2 excited state...
  11. M

    How excitation happens in power plants generator? like dams

    Hello I tried to look for the answer but didn't find enough one for being satisfied How excitation happens in big generators? If we produce electricity from electromagnet on the rotor, and electromagnets need electricity to be activated... and this happens by excitater on same rotor! and this...
  12. M

    Vibrational Excitation and Heat Capacity

    Homework Statement (a) Given V, α, κT, μJT, and CP, calculate CV at 90.0 bar and 308 K for carbon dioxide gas. (b) If carbon dioxide's vibrations were fully excited, then CV would be 4R. What's the percent vibrational excitation at 90 bar and 308K? Homework Equations Both constant pressure...
  13. S

    Calculate % Excitation of Sample X w/ Laser Pulsed Source

    Hi Everyone, I am new to this forums. I am not sure where to post but general discussion is a good place. I am trying to figure out a problem: I have a sample X in gas phase. Say it has an absorption coefficient of 9.895e-18 cm2 molecule-1 @ 532nm. I have a laser pulsed source (say 50 Hz)...
  14. F

    Particle in a box and electron excitation

    Homework Statement Hello everyone, I have a question from a practice exam I can't seem to figure out. 1. A Ca atom (atomic number = 20) is in the ground state. Light is shined on the atom, exciting the most energetic electron. Which of the following are possible quantum numbers (n,l,m) of...
  15. S

    Nuclear Excitation: Find Energy of Incoming Photon

    Homework Statement A nucleus of mass m initially at rest absorbs a gamma ray (photon) and is excited to a higher energy state such that its mass is now 1.01 m. Find the energy of the incoming photon needed to carry out this excitation. Homework Equations m^{2} = E^{2}-P^{2} possibly...
  16. C

    Excitation to higher energy levels

    If an electron gets excited from K to L shell, it will actually finish in the 2p subshell and then deexcite to 2s and 1s at the end, right?
  17. K

    Collisional excitation of diatomic molecules

    Hi, assuming I have the potential for a diatomic molecule in the groundstate i=o and excited state i=1 V_i( r ) = D( 1 − exp[ −β ( r − r_i)] )^2+ C_i Using collisional excitation with fast electrons. What is the vibrational quantum number of the state the molecule will most likely be...
  18. C

    Fluorescence Excitation and Emission Spectra

    I need help understanding the relationship between the excitation and emission spectra for a fluorescent material. This is not homework. Let's say we have the following graph which plots the two spectra for a given material: Two curves are shown - the excitation spectra and the...
  19. N

    MHB Longitudinal excitation of a sine wave

    Hi! This is a problem regarding a quarter car model driving over a sinusoidal road excitation. A sinusoidal excitation can be written on the form ze^(jωt), z being vertical. I would like to write the longitudinal excitation of a sine wave on the same form? Any hints and tips are much appreciated.
  20. D

    Is an emission spectrum really independent of excitation wavelength?

    I've often read that the emission spectrum of a fluorescent molecule is independent of the wavelength used for the excitation. But what happens in the case of a small Stoke's shift where the excitation and emission wavelengths overlap? If I use a narrow band excitation with a wavelength in...
  21. H

    Thermal excitation of electrons in semiconductors

    Which mechanism in semiconductors is responsible for electron excitation from valence to conduction band in thermal equilibrium at temperature T? Do valence electrons take their excitation energy from the lattice by absorbing phonon? If so, they can be excited at each arbitrary temperature no...
  22. A

    Selective excitation of metals for ablation

    So I've heard of certain technologies that allow for heating of a certain type of metal inside of the body using external radiation. From what I understand, certain metals can be targeted while avoiding other metals. How does this "selective heating" process work.
  23. B

    Excitation and Absorption spectra

    Hello, am working with luminescence spectra, including excitation and emission spectra. When you makes an initial characterization of a sample should be done first? an absorption spectrum? At what wavelength excitation should be performed to see the desired effect? Particularly when...
  24. E

    Is it possible to excite solid metal using radioactive material?

    Hi all, How can I excitation - ionization solid metal ? May by radioactive material which is too soft.
  25. A

    MRI excitation time vs relaxation time

    So.. if you apply a fluctuating magnetic field to an atom at its correct resonance frequency, its pole will go out of alignment of the applied field. How long does it take for the proton/electron to go 90 degrees out of the applied field vs how long it takes to return
  26. C

    Dipole excitation response function - physical interpretation

    Hi everyone, I'm a new member but it's not the first time I look at the forum. Well, I don't know if this is the right section to post my question. I think it is related to quantum mechanics interpretation too. Anyway, let's have a look at my problem. I've computed cross section for photon...
  27. T

    Collisional excitation minimum velocity

    Homework Statement A sodium atom emits a photon with wavelength 818 nm shortly after being struck by an electron. What minimum speed did the electron have before the collision? Homework Equations E_{particle}\geq\Delta E_{atom} The Attempt at a Solution For the minimum energy...
  28. D

    Excitation of electrons in atoms

    I'm curious, when an electron is bombarded by another electron or photon does the electron even jump at all if the incoming particle does not have the minimum energy to make it jump to the second orbital. That is do the electrons have some sort of knowledge before the collision occurs and know...
  29. S

    What does it mean, The Higgs boson is an excitation of the higgs field

    How come Higgs Bosons have mass if Higgs field itself gives other thin How come Higgs Bosons have mass if Higgs field itself gives other thing their mass?
  30. N

    Material has low excitation temperature

    Is there any material that can be ionized (plasma state) at realtively low temperature, say 30 or 40C?
  31. fsonnichsen

    Maximum Fluorescence Energy vs Excitation

    I have taken a time dependent fluorescence series of spectra for an ethylene glycol solution using a 532nm laser as the excitation source. I have attached the spectra to this post. Nothing looks unusual-there is a sharp notch near the 532nm line--this is due to a filter I have used to protect...
  32. fsonnichsen

    Excitation Effects for Fluorescence Spectroscopy

    I have read from time to time (e.g. Lakowicz) that the fluorescence spectrum of a substance is not generally influenced by the wavelength excitation source. On the other had there is a correlation as exemplified in excitation-emission matrix spectra for example. The obvious case is for...
  33. H

    Electron excitation and velocity

    When an electron is excited from a valence band to a conduction band by photons, its velocity changes. Do photons change the velocity or it is another process that changes it?
  34. D

    Base Excitation: Find response and transmitted force

    Homework Statement The diagram simulates a vehicle driving on a rough road. Let v=constant. Find an equation for the response z(t) as well as the force transmitted to the vehicle http://imgur.com/GUQcHx7Homework Equations x'' + 2ζω(x'-x_b') + ω^2(x-x_b) = 0 x_b(t) = X(iω)*e^(iωt) The Attempt...
  35. C

    Atomic excitation and electron orbits

    hi guys, i have a basic question over the atomic excitation and it's relationship with the hydrogen like atoms. we know while excitation the electron in the ground state jump to the higher orbits. but when hydrogen or atoms containing little principal quantum numbered orbits get excited , then...
  36. L

    Molecular hydrogen excitation levels

    Hi, I am looking for electronic excitation levels of molecular hydrogen like attached table. but there are only a few electronic states, i need near-threshold energy levels. where can i find all levels? thanks for attention http://imgim.com/5648inciz1637947.jpg
  37. jaketodd

    Electron excitation, and inhibition with EIT/CPT?

    It it being debated whether Electromagnetically Induced Transparency (EIT)/Coherent Population Trapping (CPT) can stop a molecule from gaining an electron. I want now, in this thread, to turn to the possibility of creating transparency/trapping in a molecule that would either suppress...
  38. S

    Atomic Excitation transition energy

    Hey, Here's the question Now I wanted to check if my thought process was correct and thus my formulation. Some sodium atom is initially excited, emits EM wave with stated λ and then de-excites to the ground state. However, this is Sodium so I think we approximate the energy levels...
  39. C

    Excitation current & primary current in transformer

    Transformer equivalent circuit shows that excitation current is just a tiny friction of the primary current. I always thought the pricinple of transformer was like this: voltage on the primary winding generates the current there, then flux in the core, then voltage on the secondary winding and...
  40. Islam Hassan

    Matter as Excitation of Fields: Model or Reality?

    Are SM particles expected to really be i) simple excitations of their associated fields, ii) particulate matter which happens to be very conveniently (and precisely) modeled as excitations of such fields or iii) we can't judge one way or the other in the present state of our knowledge? If they...
  41. C

    Is an electron an excitation in a magnetic field?

    I didn't really know how to word this question, but what's confusing me is this: I was researching "what is an electron" and I read in many places that "an electron is an excitation in a magnetic field". But what does this mean? I thought that an electron is just a particle with mass and charge...
  42. B

    How does a lithium boarte bead stabilize itself after xrf excitation?

    My probelms is thus: I have a numerous samples that my company runs and I am trying to figure out how the lithium borate fusion of samples like silicon dioxide or Fe-Ti stabilize after excitation from xray to fluores. Becasue the way I would think is that the smaple/LiT is stable before...
  43. V

    Chemistry Full Excitation of Molecular Vibration Modes

    Homework Statement Given the relationship Cp/R as a function of Temperature, approximate the number of fully excited vibration modes at a given temperature for a given molecule. 2. The attempt at a solution I have looked through several textbooks and many web sites, but I can't find this...
  44. K

    Excitation energy of quantum dots

    Hi, i saw these parameter, excitation energy & distribution energy, in structure which have quantum dots with superlattice, and i didn't have any idea about it. can you give me definition or physical explanation about these parameters. Thank you.
  45. C

    Timeframes of Electron Excitation: Phosphorescence Excluded

    Excluding the process of Phosphorescence, an electron in an excited state will return directly or with a intermediate step to its grown state (like in a ruby LASER before the stimulated emission, where first absorbs a green photon, drops to an intermediary energy level and then emits a red...
  46. S

    Excitation of identical particles

    Hi. Say you have a cluster of particles and you are probing the cluster with a dopant particle. You excite the dopant and observe its emission - this spectra is perturbed by the cluster particles compared to the free dopant. What if the dopant was the same as the cluster particles. I know you...
  47. M

    Excitation winding and fuction of AVR

    I have a generator. Single phase 220 volt A.C output Frequency 50 Hz 2000 kVA Rotor winding of my generator was burnt. It was rewinded but it burnt again after 1 day. There are 2 types of windings in stator one main winding which gives 220 volt A.C output and 2nd is excitation winding...
  48. R

    Franck hertz Experiment-Ionization vs Excitation

    Franck hertz Experiment--Ionization vs Excitation Homework Statement We performed the Franck-Hertz experiment with neon gas. As we raised the accelerating voltage, the electrons gained enough energy to raise the energy of the neon through inelastic collisions. Those electrons lose some energy...
  49. R

    Ansoft Maxwell, "cannot apply Current Excitation to non planar entity" error

    Hello I am new with Maxwell. I made a motor drawing in solidworks and imported it in maxwell. I found some tutorials, and searched on the internet but could not find answer to my problem. So when i try to assign Excitation Current to an coil i get the message Excitation 'Current1' : Cannot...
  50. L

    What's the excitation temp of He? How to get this?(DBD plasma)

    Hello. I've experiment, which makes plasma using He-1 under atmoshpere & room temp,it's to show how DBD plasma emission energy. As I know that high intensity wave length of He-1 are 588nm,668nm,708nm..etc. If take a formula, ln(a) is propotional to -1/(T-ex). ln(a) is some value.(a has...
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