# What is Resonance: Definition and 643 Discussions

Resonance describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamic system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies.Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system. Small periodic forces that are near a resonant frequency of the system have the ability to produce large amplitude oscillations in the system due to the storage of vibrational energy.
Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters).
The term resonance (from Latin resonantia, 'echo', from resonare, 'resound') originated from the field of acoustics, particularly the sympathetic resonance observed in musical instruments, e.g., when one string starts to vibrate and produce sound after a different one is struck.

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1. ### Fan-motor system resonance problem

Hello everyone, I am a student doing an internship at IMEC, Belgium. I am studying a fan driven by a motor. This fan-motor system goes into resonance at a control frequency of 36.2 Hz. This corresponds to 18.1 Hz impeller frequency. The operating range of this fan is 30 to 40 Hz, so we can't...
2. ### Functional representation of the oscillating graph

Hi; This is in fact not a homework question, but it rather comes out of personal curiosity. If you look at the graph of the two functions in the image attached, what is the simplest functional representation for such a symmetrical pattern?
3. ### I What is the function of the air cavity inside drums?

I'm trying to understand the function of the air cavity inside drums. I've read that 'The air cavity inside the drum will have a set of resonance frequencies determined by its shape and size. This will emphasize some frequencies at the expense of others.' Then what are the resonance...
4. ### Resonance of a PWM DC Circuit

I am experimenting with finding the resonant frequency of water in an attempt to disassociate the H2O bond without high voltage/current and using just tap water - no electrolytes, etc. I know how it works in classic electrolysis but that's not what I am attempting. Assume that there is a...
5. ### B Resonance state - Alternating current

In alternating current, is the resonance state that the phase angle of the current is 0?
6. ### Pulsed Nuclear Magnetic Resonance

I have found articles that show T1 and T2 values for mineral oil and I compare them to mine and there is over 50% error also I know that T1>T2 but mine numbers don't follow that scheme.
7. ### I Help Designing a Resonance Box for Tuning Forks

I got these tuning forks from someone. However, I do not have the resonant box for amplification of the sound. I decided to get it made so that I can experience the fundamental frequency (and other harmonics) more clearly. I am planning to provide this design. In summary, the box would be...
8. ### Resonance in transmission lines

I've calculated the relationships between the input impedance, line impedance and terminal impedance for a mismatched transmission line (parallel-wire type and of length ##l##). I'm now asked to consider the case where "the source [an oscillator] is in resonance with the line". What exactly does...
9. ### Peak of the amplitude resonance curve

Hi everyone, I'm stuck on how to show the peak of the amplitude resonance curve is at wd = w0√(1-1/2Q^2), where Q = w0/γ. My first instinct is to take a derivative of something and set = 0, but what eqn?Help?
10. ### Molecules with an extended π system well described by resonance hybrid

Homework Statement:: [...] Molecules with an extended π system such as linear polyenes and polyaromatic compounds are well described by resonance hybrids as well as by delocalized orbitals in molecular orbital theory. Relevant Equations:: N/A This is not a Homework question. I was reading...
11. ### Resonance structures

Summary:: I would like to know if my answers of each resonance structure of the eight questions is correct or not. I think the Inductive effect (induction) attracts electrons and affects up to three bonds as electron attracting group. And the Mesomeric effect affects Pi- bonds as long as there...
12. ### Engineering Resonance in AC circuits

Here's my attempt at a solution.
13. ### Question about the energy stored in an RLC parallel resonant network

Hi, I've a doubt about how to the energy is stored in a 'real' RLC parallel resonant network feeds from a sinusoidal source. Take a 'real' RLC parallel network having a resistor ##R_s## in series with the inductor ##L_s## (modeling its loss) with the capacitor C in parallel and consider it in...
14. ### Engineering Finding the parallel resonance formula

Hello! I'm having trouble with getting the right result in this litle example. Consider this admittance $$C + Cs - w^2_{pr} CCs$$ Now to get the resonance we need to set the imaginary part of the admittance 0.I did that like this $$0 = C + Cs - w^2_{pr} CCs$$ Now I need to get ## w^2 ##...

16. ### Chemistry Drawing resonance structure for this O-CH2 ion

ion shown: My answer: the following is the answer of the question: I identified the major contributor correctly, but the resonance structures, but the second resonance I drew is missing in the answer sheet. Can anyone tell me why the second resonance structure is not part of the answer...
17. ### Chemistry Drawing resonance structure for SO42

I was told that there are six resonance structures for SO42-, as shown below. I am wondering why this structure with single bonds is not one of the possible resonance. I understand that it is unfavorable as the formal charges are spread out over all four atoms, but shouldn't is still be a...
18. ### Finding the resonant frequency of this "discriminator" demod circuit.

This is the FM demodulation "discriminator" circuit. It is one of the simplest analog demod setups one could think of. An RF (FM) voltage signal is applied at V12 and the voltage at ' a' ' is supposed to contain the AF signal in its amplitude. The idea behind the circuit is that it resonates at...
19. ### Beats and Resonance - How to Find the Length With only Frequency?

So, my thinking was that we use the formula V=f(lambda) and substitute the f so, V = 440(lambda) but then i don't have another number to cancel or rearrange by. And since closed air columns have the fractions of 1/4, 3/4, and 1 1/4 (5/4), we could divide by those?
20. ### Coupling of resonant modes in a 1D Photonic Crystal

In 1D Photonic crystals, a defect can be introduced to create a defect/resonance mode and enable transmission. At first considerations, the thickness of the single defect layer determines the transmission frequency. Moreover, if it is a half-wavelength layer it will enable a resonance condition...
21. ### Questions About Highly Coupled Magnetic Resonance

This is one of very few in-depth sources of information I can find online about Highly Coupled Magnetic Resonance...
22. ### Resonance vs. Conservation of Energy

I can solve the equation for a damped oscillator with a forcing function. I can then plot the Kinetic and Potential Energy. They will be out of phase, of course (KE peaking when PE is zero, and vice versa) And we know that when the input frequency is close to the natural frequency, the system...
23. ### Steric inhibition of resonance

Is there steric inhibition of resonance effect acting on acetate ion of acetic acid by which it breaks the equivalent resonance of COO group and destabilize the acetate ion? Please help me to understand this

Hi, can anyone provide literature that explains nuclear magnetic resonance spectroscopy in terms of a quantum mechanical theory? Could QED explain NMR in its entire phenomenon?
25. ### Understanding frequency calculations of an object (e.g human body)

Apologies for the noob question. The frequency of the human body can be calculated based on weins law as follows: Wavelength = 0.002898/310 = 0.00000934838 m Plugging this into the equation λν = c we get frequency = 299792458 / 0.00000934838 = 32069 Ghz Elsewhere, I see that the resonant...
26. ### I Confused about fluorescence at resonance

Hello! I am a bit confused about a resonance signal that is obtained by measuring the fluorescence signal from overlapping a laser beam with some atoms. Based on the signal shape, the maximum number of counts corresponds to the resonant frequency of the transition (ignoring for this questions...
27. ### B Mechanical Resonance and Natural Frequency at the Atomic/Lattice Level

How do we explain resonance of a complex system (say a bridge) at the atomic level? What's happening to its molecules when it's oscillating at resonance, and does that have anything to do with the frequency at which the molecules oscillate in the material?
28. ### I Cavity resonances between two long parallel plates

Consider two rigid and infinitely long parallel plates (say they are of infinite length in X direction, so running from -inf to +inf in X axis) separated by a distance d (say measured in Y-direction). Let the space between the plates be filled up with a fluid that supports acoustic waves. If we...
29. ### Chemistry Thiocyanic acid resonance

I'm aware that the structure on the left is correct, but given that the formal charges are the same for each structure, I can't figure out why hydrogen is more likely to bond to the sulphur atom than it is to the nitrogen atom. Thank you for your help here!
30. ### B Kill drum head overtones without anything touching the drum head

Hi All, I considered filing a patent for this invention, but instead decided to publish it so people could use it to advance the state-of-the-art in drums. You don't need to add tape or pillows to your drum heads to muffle the overtones. Using tape or pillows also kills the strike of the...
31. ### Synchronising Metronomes in a Spreadsheet

The Royal Institution Lectures are on BBC4 and iPlayer now: https://www.bbc.co.uk/programmes/b00pmbqq They'll be on the RI channel a month later.
32. ### I Resonance gets sharper just by increasing the resonance freq, why?

The ##Q## factor of an oscillating system is defined as ##\omega_{r}/\Delta \omega##, where ##\omega_{r}## is the resonant frequency, and ##\Delta \omega## the resonance width. As I understand, ##Q## measures how sharp the resonance curve is. Why is it that the resonance curve gets...
33. ### A Coorbital question

I was working on a proposal for a spacecraft , and suddenly realized that the ideal orbit may be a high inclination type of near-Earth coorbital called a "retrograde satellite" or RS orbit. Do you know of: * A person who can compute 100 years of coorbital stability using three body (sun...
34. ### I Find the practical resonance frequencies in a system of linear differential equations

Hi all, I would like to know what is the equation upon which I can use to determine the practical resonance frequencies in a system of second order, linear differential equations. First some definitions: What I mean by practical resonance frequencies, is the frequencies that a second order...
35. ### A Fano resonance theory

Good evening. I wanted to study the theory about Fano resonances. I tried to read the paper but it doesn't seem very pedagogical to me and I coudn't understand all the details. Are there any notes or any good book where I can find a more precise theoretical description? Thank you
36. ### Determine the capacitor value so that this circuit is in resonance

L=100mh=0.1H ω=10^3 rad/s -> f = 159Hz XL= ωL= 2πfL= 2π*159*0.1= 99.90 Ω Z parallel = [(XL∠90º)*R2] / [(XL∠90º)-R2]= 37.13∠-21.8º XC= 1/ωC= 1/(2 π f C) I don't see how I am supposed to get to C
37. ### A Rabi frequency and "optical resonance and two level atoms" by Allen

This might not really be that tuff a question, so the Rabi frequency... the definition that I seem to find in multiple locations seems to be in agreement with what's on wiki here: "https://en.wikipedia.org/wiki/Rabi_frequency" but when I am reading a book by L. Allen "optical resonance and two...
38. ### Usage of absorption and magnitude mode spectra in nuclear magnetic resonance

In nuclear magnetic resonance, when should one process spectra in absorption mode and when - in magnitude mode? What is benefit of using the first one and the second one? For example, I need to integrate spectrum. In this case, what should I use - absorption or magnitude mode?
39. ### Understanding resonance in a spring

I have the equation $$\frac{d^2y}{dt^2} + 5y = 0$$ where I've worked out $$y = Acos(\sqrt5t) + Bsin(\sqrt 5 t)$$ $$y'' = -5Bsin(\sqrt 5 t)$$ using $$y = e^{\lambda x}$$ and using y(0) = 0 (the spring is released from equilibrium) so an external force $$Acos(\omega(t - \phi))$$ is applied so...
40. ### Is this an allowed solution? - 2nd order harmonic oscillation

It is true that at resonance frequency the phase-shift between input and output is 90 degrees, so my mind would think that this is ok. But I am kind of unsure because of the whole dividing by zero part. If this isn't allowed: is there any way to calculate/measure the damping coefficient with...
41. ### 1-D wave resonance in the case of an Open-Ended String

## \frac{1}{v^2} \frac{∂^2y}{{∂t}^2} = \frac{∂^2y}{{∂x}^2} ## and general solution ## y = A sin(kx+ωt)+ B cos(kx+ωt) ## http://blogs.bu.edu/ggarber/archive/bua-py-25/waves-and-sound/standing-waves-in-strings-and-pipes/ In case fixed at both ends The condition is ##y(0,t) = 0 ## and ##y(L,t) =...
42. ### What is the governing equation of a spring with sinusoidal excitation?

Hi, Most of the spring vibration lectures assume spring to be fixed on one end and mass on the other end [Example]. In my case, spring has a sinusoidal excitation on one end and mass on other end. Pl. refer the image below. How to get the governing equation? With that I also want to find the...
43. ### Resonance escape probability after a change in temperature

Hi, I'm reading Lamarsh's book "Introduction to nuclear reactor theory" and in chapter 7 he discusses the influence of temperature on the resonance escape probability. He states that after an increase in Temperature, as a consequence of Doppler broadening, the microscopic absorption cross...
44. ### Acoustic resonance - Absorption vs Transmissibility

Hi everyone. Firstly, I'm not a physicist, so relatively "intuitive" explanations would be greatly appreciated :) I'm confused by the following: Let's say we have a partition / wall, which resonates at a specific natural frequency. If the resonance is relatively high Q (low damping), then...
45. ### What tutorial for Resonance structures?

Hello everybody, I am stuck with drawing resonance structures for different types of compounds. Do you know any tutorials or any methods to master drawing resonance structures? If yes, please be kind enough to drop some links and statements below. Thank you very much in advance.
46. ### Resonant MEMS accelerometers

Hello, Suppose that I have a resonant MEMS accelerometer. It has a suspending beam (resonator) and I want to apply an AC voltage to the beam which will be at beam's resonant(natural) frequency. When I do this, I will create a standing wave pattern of acoustic waves (vibrations) inside the...
47. ### Acoustic resonance

I am trying to understand the physics of resonance phenomenon. One can find the resonant modes of a water filled spherical cavity either analytically or by using the FEM eigenvalue analysis (K-ω2n M = 0, with K and M being the usual stiffness ans mass matrices in FEM). For the later, we usually...
48. ### Mechanical Resonance Lab Questions

Hey everyone. I have a lab with questions we have to answer but I don't really have any access to equipment. I still have to answer the questions to the best of my ability and any help will be appreciated! 1. Homework Statement A string is attached to two retort stands and two equal masses...
49. ### Does resonance always affect acidity and basicity?

Does resonance affect the acidity of an acid (or the basicity of its conjugate base) if the resonance isn't delocalizing the charge on the atom that is directly attached to the atom with the proton, hydrogen itself. For example a benzene ring with a carboxylic acid group attached to one side...
50. ### What constitutes a closed end in acoustic resonance in tubes

Dear all, For my students, I'm currently trying out some experiments they can do to simulate acoustic processes. One of the topics that we will be discussing is that of standing waves. Although I have never done it before--I come from a completely different background--I want to create...