Measurement Definition and 1000 Threads

Homework Statement I am having a hard time understanding the length measurement in the problem. We went over this example in class and the length, L, was something I didn't realize until now. Question: A 6-ft-long steam pipe is made of A-36 steel with σ=40 ksi (yield stress). It is...

Hello, The quantum zeno effect is well understood and experimentally confirmed as regards polarization measurements (as discussed here). It's the quantum analogue of "the watched pot never boils" as it allows "continuous" measurement to inhibit certain state evolutions. Does the effect...

Hi! I found a few old threads lying around regarding this, such as this one, but I thought I'd start a new one asking the question in my own way. So here goes. Is the uncertainty described by the Uncertainty Principal a result of the fact that by measuring something we affect it, or a...

I'm having a gap in understanding the relation between them, and resolving my confusion is really appreciated. For example, the Hamiltonian operator, why do we call its eigenvalues energies? how do we actually measure it in the laboratory, quantum mechanically? And maybe I need a better...

We define time by the rate at which physical processes (i.e. clocks) tick. With atoms for example we can define time by their energy transition rates such as in atomic clocks. But, what before atoms existed? Current cosmology theories make statements such as that '0.5 seconds after the Big...

Suppose I have a particle confined between 0 and d on the x axis, and it has some wavefunction, if I measured the particle to be between some small interval [a, b], would the wavefunction collapse into a rectangle-like function with equal prob. density on the interval and zero outside? or what...

Homework Statement I'm currently writing a program that will read in a list of gaussian distributed random numbers as an array and will make a 'measurement', that is they will be assigned to another array with an associated error. This is to try and simulate the communication of Alice to Bob...

Homework Statement You measure 50V with a voltmeter, which has 300V as the max. input voltage. What will be the relative error (h%) of the measurement? Homework Equations The Attempt at a Solution hi i divided 50v / 300 V and get = 1,66 and divided it by 100 to get relative error...

Hi, Homework Statement We ran an experiment for confirming the linearity of Faraday's Law (the relation between EMF and the rate of change of flux), by plugging a magnet to a motor rotating in the axis of a solenoid (inductor). In my graph of the amplitude of EMF wrt time, I noticed some...

It is proposed to use a katharometer to mesaure the amount (about 5%) of oxygen in nitrogen, in the presence of a small amount (0.5%) hydrogen. How constant would the proportion of hydrogen have to be in order to limit errors in measurement of % oxygen to +/- 0.1%? The thermal conductivities...

Hello. I was just wandering if anyone could help. I've been doing a couple of statistics questions, and when they ask for some questions, I am not sure if I have an appropriate understanding of what the right answer should be. I would really like to understand this material, so what I want to...

Hi everybody. I have a quick question regarding the relationship between the uncertainty principle and the measurement postulate. According to the former, the higher our certainty is about the position of a particle, the lower our certainty is regarding its momentum, and vice versa. This...

Although it is well known that a series of individual photons will build up an interference pattern in a double slit setup, there have been few (if any) experiments where such a pattern is built up by sending photons through one at a time. Here is a great experiment from one of the top quantum...

Homework Statement I have to design a scale to weigh something under 1kg and all am given is a yard stick, 10 ft of fishing line, a 500g known standard mass, and a protractor. Use an angle measurement for weight. Don't just balance weights on a see-saw Homework Equations - The...

Homework Statement I have attached the photo of the circuit. My doubt in the circuit is that, I could not exactly figure out what the diodes do. The description says it is used to set the input of the op-amp to 1.6V above v-. But how exactly does it achieve that? Can somebody show it...

I apologize in advance if this has been asked many before, but I didn't see anything that answered my question on the first page of threads. Take, for example, an isolated subatomic particle which breaks down into two entangled particles. From what I've read, each of these two particles...

Hello, I was viewing a lecture of one of the professor's most possibly in MIT who demonstrated in the class room, by calling a boy and measuring him, while standing, a certain measurement say 5 ft. After that he asked the boy to lie down and again measured him and found that there is a...

I have been going through the following interesting paper on the foundations of Quantum Mechanics: http://arxiv.org/pdf/0911.0695v1.pdf 'We define the state of a system as that mathematical object from which one can determine the probability for any conceivable measurement. Physical theories can...

Author: Glenn F. Knoll Title: Radiation Detection and Measurement Amazon Link: https://www.amazon.com/dp/0470131489/?tag=pfamazon01-20 Prerequisities: Sophomore (2nd year uni) level courses in modern physics and EM, mathematics through differential equations, Level: Undergraduate...

Do you believe that "conscious" observation has anything to do with "collapsing" superimposed quantum states, or do you simply believe that interaction with a macroscopic, or sufficiently large system, is what causes superimposed quantum states to collapse? Why?

I want to measure ac voltage raging from 60v to 300v using microcontroller i have figured everything else out except how can i use 220v transformer(to step down the voltage to measure) when input is 300v one solution is to use simple resistors based potential divider to attenuate 300v to 220v...

Homework Statement This really is not a homework problem but I am studying for the qualifying exam upcoming. I came across an objective that I am not familiar with. I'm given a wave function made of a linear combination of spherical harmonics with complex coefficients. I'm asked to...

Homework Statement Spin-1 Particles prepared in the state: $$ |\psi> = \frac{2}{\sqrt29} |1> + \frac{i 3}{\sqrt29}|0> - \frac{4}{\sqrt29} |-1> $$ Where I'm guessing the ## |#> ## represents the spin state of -1,0 or 1. I'm looking to find the results of a measurements of the ## S_x ##...

Hi all, Just have a quick question regarding the measurement of vapor pressure. Firstly, let me explain my scenario. I am carrying-out some measurements of steam condensation in a vacuum. The steam is being condensed in a air-cooled heat exchanger. Initially, I let in a quantity of steam...

Hello. To give some more information on what I am to use this for: I have two signals. Both are periodic sine waves with the same frequency, but with a constant phase difference. Let's call one of the signals for ref (reference) and the other sig (signal). They can look like this: ref(t)...

Homework Statement Mercury is poured into a U tube. The left arm of the tube has a cross sectional area A_1 of 10 cm^2 and the right arm has a cross sectional area A_2 of 5 cm^2. One hundred grams of water are then poured into the right arm of the tube. A: Determine the length of the...

We recently had a long thread https://www.physicsforums.com/showthread.php?t=666861 about cases where raising and lowering indices isn't completely natural, i.e., where a vector "naturally" wants to be upper-index or lower-index. If you have a metric, then it's pretty clear to me what...

Hello, I recently read some texts which says that in a SINGLE measurement you can measure position and momentum to an arbitrary accuracy, assuring that that's not what HUB talks about. That confuses me, because I learned that HUB is there NOT simply because some property of QM prevents us...

I have been wondering what type of measurement is used to measure the space inside of a four dimensional (space, not time) object. For example, a one dimensional line's distance gets measured, a two dimensional object's area gets measured, and a three dimensional object's volume gets measured...

Light years-I just don't understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldn't they view the distance of let's say stars very differently because it...

http://www.spacedaily.com/reports/Chinese_scientists_find_evidence_for_speed_of_gravity_999.html Done by the Institute of Geophysics at the Chinese Academy of Sciences using Earth tide measurements. The conclusion is that it is the speed of light. http://en.wikipedia.org/wiki/Earth_tide...

Hi everyone, This is really annoying me, so, I am aware of the story why oxygen was replaced with carbon-12, (because chemists were using natural occurring oxygen which was a mix of oxygen-16,17,18 and therefor was an avg?, but physicists wanted pure, isolated oxygen-16 so there was two...

Professor of Physics History at CalTech, Dr James Woodward has been investigating an idea called the Mach Effect, which is supposed to be based on Mach's Principle and which is claimed to allow a means for propellantless propulsion without violating Conservation of Momentum. The idea is that...

Hi, I would like to use a Hall Sensor (e.g. http://fwbell.com/Category/2.aspx) or a Hall Element IC, like the AD22151 device for magnetic field measurement with a range from 0 to ca. 0,5 mT with a resolution of 250 nT. (500 ppm) The temperature fluctuations are max 1 C. Do you think I can...

Does anyone know how to measure the frequency of a magnetic field? They sell handheld meters but they only measure Mhz and higher

Dear all, I am new in this forum; from a first sight I realized that you can help me to clarify a doubt. My experiment requires the measurement of spectral trasmittance of a simple by using a white light source (400-800 nm) and a silicon photodiode. I know that a proper measurement require to...

Dear All Does anyone have any idea about how to determine the concentration of liquid urea. The concentration is a bit higher (0.5-1.5 mol/L). Is there any laboratory techniques or Kit? I looked for and found everywhere the method to measure the amount of urea in blood and urea but what I want...

when we have a certain state ψ(t) and it is acted on by an operator A of eigenstates a, b, c and eigen vectors la>, lb>, lc> does it mean that after measuring A ( if the result was 'a'), the state lψ(t)> becomes in state la>?

As the Title describes, Is the measuremet problem completely solved by the decoherence Program? In specific I would like the following question addressed. Is there is clear explanation as to what it means to Record Infromation? Can it explain the behaviour of a photographic plate? What happens...

In any physical measurement we often refer to two terms... 1.'Order of Magnitude' of certain quantity 2.the number of 'Significant figures' What they actually mean?

came across this article thought everyone here would be interested in it http://www.sciencedaily.com/releases/2012/11/121101141107.htm essentially they are measuring the particle and wave properties at the same time of photons.

[b]1. The problem statement: all variables and given/known Describe a Non-Local Expirement that will lead to the conclusion that a body is in fact in a revolving system and not a system of constant acceleration. Non-Local meaning that the expirement uses 2 measurement instruments at 2...

Homework Statement 5. What is measurement technique in impedance analyzers? 6. Draw the circuit of a two terminal impedance measurement. 7. Draw the circuit of a three terminal impedance measurement. 8. Draw the circuit of a four terminal impedance measurement. 9. How can you calculate...

Hello All, I am experimenting with DC motors and different speed settings, and I am looking for a way to measure RPM at different voltages and loads. I have been looking at different tachometers and trying to determine what my best option is. The reading does not have to be super sensitive...

How did we measure the gravitational constant G = 2.034 x 10 ^ 17 cm ^ 2 and the Earth average density (specific gravity) p = 3.45 g / cm ^ 2 s ^ 2.

Homework Statement Alright, so there is a problem in the Townsend quantum mechanics book that reads: What is the probability that a measurement of Sx will yield the value hbar for this state: The state is given by: |ψ> = 1/sqrt(14) * (1,2,3i) (But the vector is represented as a...

I'm just wondering... Regarding the single & double slit experiments... Why does every interpretation say that the photographic screen is 'measuring' the position of the particle traveling towards it? Why not say that the photographic screen interacts with an electron that is spread out...

So in my quantum class we learned that if you measure spin in one direction and get h/2 and then in another direction that it will be (plus or minus)h/2 as well. I was wondering how you would know the probability of it being the positive value vs the negative value. It's a function of the...

Using an EPROM as a UV detector. I was planning to make a UV meter using an EPROM. The idea was that ultraviolet light erases an EPROM. When a fully programmed EPROM (all zero's) is exposed to uv light I should clearly see the number of bits (one's) increasing. So I have built a small...

Hello, I was just curious about expectation values. One of the postulates of quantum mechanics state: The only possible results of a measurement is an eigenvalue of the operator. Now, is the expectation value considered a measurement, thus considered an eigenvalue? Thanks!