Measurement Definition and 1000 Threads

Pardon me for my ignorance. This is a question of curiosity. I look for a concise logical argument as to why the community believes the following hypothetical situation and explanation is wrong. What justification is there for believing in waveform collapse at time of measurement? Is it...

Hello everybody ,A friend of mine told me that best way (The most accurate) to do this is grating diffraction experiment , What u think? Thanks in advance

Hi: I have been working in this Project for a while now and I would like to share the results with you. Still needs some improvements; but it appears to be working fine so far. Please let me know your suggestions and ideas. Thanks.

Homework Statement Homework Equations The Attempt at a Solution I have managed to do the first 3 parts of the questions. The last two 4 markers are the ones I am having difficulties with. I have tried using the expansion postulate which states the wavefunction is equal to the...

Hi all! Basically I will soon be required to measure the torque required to drive a plunger pump which operates by an eccentric cam on the pump's driveshaft pushing a plunger up and down. So obviously the torque will vary through the driveshaft's revolution. The setup is as follows: Motor...

Homework Statement I did an experiment to measure air flow using a pitot static tube and a venturi meter. First attempt: I connected both long and short manometers to the pitot static tube. Then I switch on the fan. The difference in manometer reading is 0.59kPa, which is the pressure. Then I...

I am asked to indicate the uncertainty on the radius R of rotation of the plumb bob. Please see picture. Basically, there is a vertical shaft, over which is attached a horizontal shaft and a plumb bob is hung over with a thread on the horizontal shaft. The bob is attached with a spring to the...

I was just wondering if there's a way to measure pain. I figured it'd be and equation like current. Like voltage would be the amount of pain, ohm would be a persons resistance to pain, and current would be the pain they actually felt.

Hi, I am looking for an introduction to heat capacity measurements at low temperature (10K). (For example for producing the linear dependence of the electronic heat capacity on T). I fail to find a simple introduction. Can anyone mention keypoints or a good source? Thank you!

Is there a way in electrical engineering where I can convert 230 KV to 5 V such that the 5 V wave has same amplitude, phase and frequency as that of 230 KV.

Hi, My question is partially motivated by this discussion. Suppose we have a pure state that is in a superposition for a certain basis, e.g. ##\left|\psi\right\rangle=\alpha\left| 0\right\rangle+\beta\left| 1\right\rangle##. Now a colleague of ours measures the state with respect to that...

1.What do watts do and how do they affect an electrical device like a motor? 2. what do amps do and how do they affect an electrical device like a motor? 3. what do volts do and how do they affect an electrical device like a motor? I understand what these measurment are and how to solve for...

Hi! I'm breaking my head about the following problem: Consider an A/C at a certain velocity flying at a certain altitude. The A/C measures it's speed via the difference in total- and static-pressure and applying bernoulli. Now the aircraft accelerates. What happens? At this point I get...

Hello all, I have to measure the compression strength of a porous ceramic body (d=L=10 mm) using advanced force gauge, mecmesin and don't have any experience with it. The simple procedure, which I followed, was to measure the force at which the sample started to break, divided by the cross...

Decoherence relationship to the "measurement problem" I have heard the argument that "decoherence" in quantum states causes the quantum collapse to occur, and that this solves the "measurement problem". But I'm still left with a nagging question... Does decoherence only produce quantum collapse...

I'm supposed to be working with an STM in the coming weeks to determining the Fermi Level of some semiconductor diamond films. I was bombarded with a lot of information by my lab supervisor and the bit of my notes about the calculation just says "Differential of voltage vs current allows us...

I recommend the following paper by Robert B. Griffiths on developing the theory of quantum mechanics without giving a special role to measurements: http://arxiv.org/pdf/quant-ph/0612065v1.pdf In my opinion, it does not answer all the questions about locality and realism that come up in...

Hi I saw something in Wikipedia and I am confused. I saw something like this 2.0 cm -/+ 0.05 cm Whats that mean? My first opinion Between 1,5 and 2,5 My second opinion 1,5 cm or 2,5 cm

like for example digital unit measurement for clear images in devices is ...pixel

Hello, If I have a measurement of 1cm, and have an absolute error of 0.1 cm, I know that I can write my measurement as (1±0.1)cm. If I want to write it with its relative error instead of an absolute error, can I still use the bracket? i.e) (1±10%)cm ? Thank you!

I need to collect data via measuring EMG signals in the upper arm. I have standard AgCl stick-on ECG electrodes. My question is, if I can use normal alligator clip cables for collecting this signal from the electrode and feed it into an instru-amp? Will this affect the signal strength and/or...

Hi. I have a problem understanding a question for my electronic engineering course. We have a subject that's directly translated to 'the knowledge of electricity and measurement techniques'. I do hope this is the correct forum to ask for help at. Homework Statement Given the...

Can someone recommend (if possible) a way to detect the amount of helium in a given enclosed space? I'm designing an experiment in which I will need to measure the amount in an otherwise vacuum.

Thanks for the answers on my previous thread, it made some sense, and if I'll reply if there's further misconception. My new question is quite connected to the famous Andromeda paradox. So it's stated that the Andromeda is far away and moving towards the galaxy will cause the observer to have...

Homework Statement Suppose the angular wavefunction is ##\propto (\sqrt{2} cos(\theta) + sin (\theta) e^{-i\phi} - sin (\theta) e^{i\phi})##, find possible results of measurement of: (a) ##\hat {L^2}## (b)##\hat {L_z}## and their respective probabilities. Homework Equations...

If we have a qubit in a mixed state, let say 1/2(+><+)+1/2(-><-) and we measure it. Is then the result a pure state + or - ? If this is the case, then the entropy of the system decreases. Now the question another way round is : Suppose we measure a quantum system without gaining...

An electrocardigram measures the electrical current in the heart by using several "leads". These leads have +ve and -ve ends. http://www.heartaxis.com/ If you take a look at the interactive FLASH about 1/4 of the way down the page (yellow arrow and green line ppd to each other) and the...

According to "Physics for Engineers and Scientists by Ohanian and Markert, a second is the time needed for 9,192,631,770 vibrations of a cesium atom. In 1971, Hafele and Keating put four cesium-beam atomic clocks aboard commercial air liners which were flown around the world - two eastward...

Hello friends, Most people that I heard put uncertainty as an intrinsic property of the universe which is evident when we make a measurement. But to me it seems that intrinsic property and making a measurement are two entirely different things. If uncertainty were to be just(purely)...

Propose this measurement: It is a well know interference measurement, but now asymmetrical. Suppose the red path is 1 m and the blue path 10 m. If you measure the time between detector 1 and 2 I expect you will find two times: 3.3 ns and 33 ns. Then you know which path the photon took...

Homework Statement Given the wave function psi(x,0) = 3/5 sqrt(2/L) sin(xpi/L) + 4/5 sqrt(2/L) sin(5xpi/L) in an infinite potential well from 0 to L, what is the expectation value <x> and rms spread delta E = sqrt(<E^2>-<E>^2) Homework Equations <x> = integral from 0 to L of psi*xpsi dx...

So this semester our lecture explained and showed us the double slit experiment. And it he explained to us the uncertainty principal that the act of observation can change the result. However this is the part where I kind of a have a problem with.. Since quantum physics is based on the...

Halo everyone. I am new to here! I am working with a project of ocean wave energy. I would like have a device that can measure the wave length, pitch those wave parameter when I testing my wave energy device. Anyone have a clue what kind of device can complete my task?

Homework Statement Given the following wave function for hydrogen: psi(r, t=0) = (1/sqrt(10))*(2*psi_100 - psi_210 + sqrt(2)*psi_211 + sqrt(3)*psi_21(-1)) where the subscripts show n, l, m_z, respectively, and the psi_nlm_z are already normalized. - At t=0, we measure and find l = 1...

How does the Copenhagen interpretation motivate its claim that the wave function of a quantum system collapses when a property of the system is being measured? I mean, was there some problem they were trying to solve by introducing the notion of wave function collapse? What would happen if the...

What can a gaussmeter tell me about a metal? I am just experimenting with various metal disc samples by setting them on the Hall probe of a gaussmeter. I have the meter zeroed out, then I pace the metal on the probe. The metals all effect the field measurement in different ways, but I...

It is often said that non-commuting observables cannot be simultaneously and precisely measured. The rough idea is that the procedures to measure each observable are different. Is the statement strictly correct? If so, what is the mathematical argument? Is it possible to use Ozawa's...

I have a couple of questions about what total harmonic distortion is, and what the measurement means. The definition I've read most places is: \frac{D}{S} × 100% , where S is the amplitude of the fundamental frequency, and D is the amplitude of the sum of all of the harmonics. A common...

Hi All, I would like to know why the neon lamp is used to measure electrical polarity. What is the working mechanism involved. Best wishes, DaTario

Here's what I'm thinking. The sun is too bright to measure directly with our equipment. If I calibrate without a filter, and capture the reference spectrum with and without the filter, then I can model how the filter changes the spectrum. This way I can capture the sun spectrum with the filter...

Hi, I know the common proof of the no-cloning theorem assuming the cloning apparatus acts unitarily on the system and leading this to a contradiction. But what about a non-unitarian apparatus that involves measurements? I'm pretty sure cloning is still impossible, but I don't know how to...

Homework Statement Two sources, A and B, emit a sound of a certain wavelength. The sound emitted from both sources is detected at a point away from the sources. The sound from souce A is a distance d from the observation point, whereas the sound from source B has to travel a distance of...

Hi, I was just writing another thread when I stumbled upon something strange: What if I now make a slight change and replace ##\bf{b}\rightarrow-\bf{b}##? The expectation values containing ##\bf{b}## change signs and I get $$\left|\frac{1}{\sqrt{2}}-0\right|=\frac{1}{\sqrt{2}}\leq...

Hi, I'm trying get a better understanding of Bell's inequality in the form $$\left|E\left(\bf{a},\bf{b}\right) -E\left(\bf{a},\bf{c}\right)\right|\leq 1+E\left(\bf{b},\bf{c}\right)\enspace.$$ I'm considering the Bell state $$\left|\psi\right\rangle=...

Hello, I was wondering if anyone can recommend any good articles or journals with valid and good velocity data for flow from an impinging jet on a flat surface with an approximate Reynolds number of around 75,000 to 90,000? I have looked and seem to have lots of data for heat coefficients but...

If we entangle particles and separate them by a large distance, can the action of measuring one cause decoherence at the other's location? If yes then does this violate relativisitic causality? Could we not use this process to transmit information instantaneously? If no then why not? Is there...

Hello, I don't seem to know how to ask google this question so I thought I'd see if I could get an answer from here. Say I have 400 measurements of some variable. I take a sliding window of 50 events and take the standard deviation of each set of 50 events. That would be 350 measurements. Now...

Hi PF people, I am brand new to PF and this is my first post so please excuse and help correct any mistakes I make. My question is about time, the perception of time and the units we measure it in. I figured I would start this question with a statement because if my general understanding of...

I have just completed an experiment on principles of lasing, constructing a laser and measuring the beams intensity distribution. This distribution of the beam was measured using a detector mounted on a traveling microscope. The detector had a pinhole cover such that only a small fraction of the...

Hey guys, I know you all wish you never had to do all the weird conversions required for our current system of measurement. I know I'd rather convert 17km to m than 17mi to feet or ever inches. I thought that since I know so many people who would rather just do the easy metric conversions...