Frequency Definition and 1000 Threads

So the frequency in the power grid is 50 - 60 Hz depending on country's electrical standard. If I have a ~2000 watt heater that runs on 220 volts ~ 9 amps at 50 Hz, would increasing or decreasing the frequency effect the power output of the device. For example if I make the device run at 75 Hz...

Homework Statement Homework EquationsThe Attempt at a Solution [/B]

Homework Statement Calculate the frequency of a bead with a mass of m vibrating on a parabolic track equals to y=Ax2 Homework Equations F=ma The Attempt at a Solution Looking at the bead at any point which isn't equilibrium, I have: 1. may =N-mgcosθ 2. max=mgsinθ I tried to look at a...

Hello, I am just wondering whether it is theoretically possible to create radio waves through bioluminescence. I realize that most organisms produce only UV to infrared light. Are there such compounds out there that would allow an organism to make radio waves instead?

I'm doing a high school paper on the effects of frequency alterations on a radar image. Can someone recommend a book which I can use?

Hi, I am struggling to understand the maths in the text shown below. (1) How does: r(t) = Acos(wt)+Bsin(wt) become; sqrt((A^2)+(B^2))cos(wt - arctan(B/A))? (2) He states that we can represent the input as a phasor and in one of three ways but doesn't say which one. (3) He then focus on the...

Homework Statement ##N= \frac{2 f_s}{f_{lowest}}####\frac{f_s}{2} - \frac{f_s}{N}## Homework Equations - The Attempt at a Solution I have these equations listed on a formula sheet but I do not know what they are used for. It is from a chapter titled "Discrete Sampling and Analysis of Time...

Homework Statement Ultrasound reflected from an oncoming bloodstream that is moving at 28.7 cm/s is mixed with the original frequency of 2.41 MHz to produce beats. Use the speed of sound in human tissue as 1540 m/s. Assume that the frequency of 2.41 MHz is accurate to seven significant figures...

Hi, I came across a question from our weekly set of questions that involved finding the inductive reactance and capacitive reactance, ie: XL = jwL and XC = 1 / jwC. In the solution sheet, the professor wrote that the frequency, w (omega) = 10000, however, in the question sheet, it was nowhere...

Homework Statement I am NOT a student. Please forgive my asking here, but if you do choose to answer, I would appreciate it. Obviously any or all of the statements below may be incorrect... As I understand it: The more energy a photon has (I know it's also a wave) the greater the frequency...

Hello, I am studying about waves and simple harmonic motion. I have a confusion; when we studied the formula for period of pendulum and spring (T=2pi(rad(m/k))), it can be deduced that period doesn't depend on amplitude and so does frequency (T=1/f) Then we learned about how amplitude and energy...

A suspension bridge oscillates with an effective force constant of N/m. (a) How much energy is needed to make it oscillate with an amplitude of 0.106 m? (b) If soldiers march across the bridge with a cadence equal to the bridge's natural frequency and impart J of energy each second, how many...

(a) A wave traveling on a Slinky® that is stretched to 4.5 m takes 2.6 s to travel the length of the Slinky and back again. What is the speed of the wave? For this one, I did v = d/t = 4.5 m / 2.6 s = 1.73 m/s Then I did v = (1.73)(2) = 3.46 m/s This is correct (b) Using the same Slinky...

ELF electromagnetic radiation is in the range of 3 to 30 Hz. If you had a 3Hz ELF laser pointer and you had a camera that could "see" ELF, would you be able to see the intensity of the beam "flicker" at 3Hz?

I am wondering why LC tank only oscillates at resonant frequency not other frequencies? Is there a physics explanation for that?

So, I have made an experiment of a low pass filter, and made a bode plot out of it. My experiment was done 100 percent in Japanese and this means I cannot understand completely the experiment I have done. So, there is a statement there saying the higher the frequency of the input voltage, the...

Does the frequency of the main affect the performance of a microwave oven? Having moved from Europe 50 Hz to the Philippines 60 Hz I can not operate my microwave oven! Is that the reason? How to remediate? Best regards.

Homework Statement Problem and Diagram stated below System 2 Input Impedance: 1k ohms System 1 Output Impedance: 100 ohms High interpreted as Voltage greater than 2V Low Interpreted as Voltage less than 0.5V Homework Equations Capacitor Charging eqn: V=Vo(1-e^-t/RC) Capacitor Discharging...

Hi I need help understanding the frequency characteristics of operational amplifiers. I do not understand why the output of an Op-Amp behaves much differently when the frequency of the input is increased. For example during the lab when the input to an inverting Op-Amp circuit was a sine...

Hi all, I was just thinking about the Doppler effect today and I was wondering why distance between the source and listener does not affect the frequency experienced by the listener. Consider the Doppler formula: fL = fS*(v+vL)/(v+vS), with the positive direction taken from listener to source...

Homework Statement When two sound sources of the same amplitude but of slightly different frequencies n1 and n2 are sounded simultaneously, the sound one hears has a frequency equal to Ans: (n1+n2)/2 Homework EquationsThe Attempt at a Solution I have virtually no clue how that's the answer...

I am interested to know what governs whether an object in the path of a sound wave will feel force. For instance will low frequency sound have more of an effect than high frequency? What difference does the material or shape of the object have on whether it would feel any force from the...

Homework Statement Problem and work attached. It is mostly diagrams so I have just uploaded the pictures. I think what I did to determine the transfer function was correct. I'm not quite sure how to do the last section of part (a) where I need to determine the dampening, static gain, and...

I am trying to understand why/when a purely ohmic voltage divider (impedences Z1 and Z2 are both resistors) would have a delayed response for high-speed, transient changes in an input voltage? Whether the input is high-freq AC, or simply a square wave with a sharp rise or sharp drop, I've been...

Dear PF Forum, I've read the current Featured Thread in November 12nd, Lost in the Milky Way scenario. It's a good thread. But I want know what pulsar is. https://en.wikipedia.org/wiki/Pulsar A. Does pulsar(s) have unique frequency? Given the number of pulsar in our galaxy and the vast range of...

The question is: The voltage source in the above circuit is a sinusoidal AC source with constant amplitude and constant phase shift but an adjustable frequency. Calculate the frequency ω at which the phasor current I...

Homework Statement Electron with KE = 50eV is captured by Alpha particle, ie. HE++. Calculate the frequency of the emitted photon. Homework Equations KE = m/2 v^2; E=hf, En = Z^2*-13.6eV/n^2 The Attempt at a Solution Energy before = Energy after 50eV = 4*-13.6eV/1 + hf f = 1200nm

A cable with concentric PE conductor must be used with frequency converter circuits what does its means.?

Homework Statement An alpha particle: He++ captures an electron of a given kinetic energy. To conserve energy, it emits light, hf. How would one calculate the frequency? Homework Equations E=hf En = (Z^2 *-13.6eV)/(n^2) The Attempt at a Solution Calculate En. Then KE = Photon + En. Solve for...

Homework Statement Identical ropes were tied to two trees, and two men, A and B, started shaking the free ends at the same instant a short while ago (Figure 1) . Which rope has the greater tension? Which man is shaking with the greater frequency? Homework Equations T=1/f λf=v The Attempt...

This is a very fundamental question. I apologize for its simplicity. I did searches on the web but could not find a clear explanation. Whenever I read about the principles of quantum physics, I always come across a statement along the lines of: "electromagnetic energy could be emitted only in...

So I just did a lab on resonant frequency, and have to find the error of the period: $$T = 2π\sqrt{m/k}$$ m and k were measured with an error of Δm and Δk. My teacher didn't explain well how to do errors, so I just want to know if I did this right. Prorogation of Error equations: $$y=x^n ⇒...

Homework Statement The fundamental frequency of vibration of a particular string is f. What would the fundamental frequency be if the length of the string were to be halved and the tension in it were to be increased by a factor of 4? Answer: 4 f 2. The attempt at a solution We have f = f1...

If you have a one solenoid inside another (with the same number of coils of wire) the current is going through the inner one. How does the induced EMF in the outer one depend on the frequency of AC in the inner one

Homework Statement A electron cyclotron has a frequency of 2450 Hz and a magnetic field strength of 50T.? a) what's the speed of the electron? b) what was the voltage on the electron gun which projected the electron into the cyclotron? Homework Equations Givens: r=.4m B=50T f=2450Hz...

I have poorly made computer speakers - Logitech X-530. They sometimes pick up AM radio stations and pops up when lightning is turned off. What AM radio frequency is picked up by computer speakers? I am curious becaous some kinds of popping is picked up by computer speakers but it is not picked...

I have a few questions about AM, FM and PM. 1. If FM (or PM) radio modifies the frequency of the signal, how is the signal picked up without having to change the frequency constantly? 2. If PM modulates phase, which modulates frequency, what is the difference between PM and FM? 3. Why is AM...

Hi, I am studying the physics of MRI (from a conceptual NOT mathematical point of view...please don't answer with heavy maths). I understand how we can obtain a signal from a specific slice along our Z-axis. I know that we then apply a graded magentic field (frequency encoded gradient) along...

Homework Statement Consider a particle in an infinite square well potential that has the initial wave-function: Ψ(x,0) = (1/√2) [Ψ_1(x) + Ψ_2(x)] where Ψ_1(x) and Ψ_2(x) are the ground and first excited state wavefunctions. We notice that <x> oscillates in time. FIND the frequency of...

Are all the radio galaxies in the (approximarely) same distance from us? And is the reciveing frequency from all of them in radio band? I am wondering whether the difference between a radio and x-ray galaxy is their redshift or their emission mechanism ?

I believe that when we say that this is radio telescope, it means that reciving frequency of it is in radio band. And also it means an observed object by that is in a particular redshift that its emission has a particular frequency that when receives us, is in radio band. Am I right? For ex. We...

Hi, I am just trying to understand the output of a sound spectrum analyzer. There are three dimensions 1) Time 2) Frequency 3) Volume (db) I am confused about few things here: 1) How should I perceive the volume dimension here? 2) Why are the db values negative here and w.r.t what reference...

For a spring and mass system, I've learned the resonance frequency of a system increases with decrease in mass. Not sure if this case is also related but when I attach a coin sized metal onto a piezoelectric material of a smaller size, the resonance frequency range actually goes up (from...

How to integrate $$\int_{-0.5}^{0.5} {\bigg({\frac{1}{4-2e^{-j2{\pi}f}}}\bigg)}^2 df$$

Homework Statement Find the period and frequency of the motion of an electron of kinetic energy, E, 34 KeV as is moves in a circular orbit perpendicular to a magnetic field, B, of 0.270 T.Homework Equations For speed, v: For charge, q: For mass, m: For radius, R: For frequency, f...

Homework Statement A time series is sampled at 250 Hz. What is the sampling interval and Nyquist frequency of the original signal, before digitising was contaminated with noise at about 300 Hz. At what frequency would this noise appear in the spectrum of the digitised sequence ? Repeat the...

Homework Statement Homework EquationsThe Attempt at a Solution if the material are the same in both strings, then the density should be the same. v = sqrt (tension/μ) tension in the first string should be 30 kg x 9.8 m/s^2 = 294 N next, v = λƒ and string#2 needs to have twice the...

Homework Statement A metal wire is vibrating at its third-harmonic frequency. 0.32 m from one end, the amplitude is equal to one quarter the maximum amplitude. Find the length of the wire. Homework EquationsThe Attempt at a Solution I don't quite understand the question, it says 0.32m from one...

Homework Statement Homework EquationsThe Attempt at a Solution for the first harmonic, the wavelength is twice the length of string. so 0.296m x 2 = 0.592m is the wavelength with the wavelength and frequency known, we solve for v in v = ƒλ v = 0.592m x 440 Hz = 260 m/s then to solve for...

I have put together an equation whose purpose is: With a desired 'magnitude of static friction' ( μ_s ), 'fundamental frequency' ( f ), and 'tension' ( T ), initial conditions such as 'string breakover angle' ( Θ_0 ), 'nut-tuner distance' ( L_{h,0} ), and 'string diameter' ( d ), and...