Measurement Definition and 1000 Threads

"Measurement disturbs the system." Okay so I explained the uncertainty principle to my non-scientist friend, and he came up with a basic thought experiment. I know there is something wrong with it, so I read paragraph 8 from here: http://www.oberlin.edu/physics/dstyer/TeachQM/misconnzz.pdf...

Flow rate measurement: Venturi vs Sharp edged circular orifice. Help! :) Homework Statement Hello guys, I am having trouble answering these questions. I know the the discharge coefficient for a venturi is always higher than that of the sharp edge orifice. Can you guys help me out with the...

I went to see an orthopedic specialist this year, when I was 15 years and 5 months old. I am 5 ft, 11 1/4 in. The specialist looked at my then-recent X-rays and I was not even halfway done growing. (I'm pretty sure I scored a 2 out of 5.) I am due for another X-ray sometime next year, at...

Homework Statement Using Equations (A) and (B) explain how to obtain for e/m from the slope of an I vs. \sqrt{V}/{r} graph. Show how to calculate a value for the Earth's magnetic field BE using the intercept of the graph.Homework Equations (A) B_H = \frac{8NI \mu_0}{R \sqrt{125}} (B)...

Hi everyone, I was thinking about what it means to talk about the "momentum of a particle" and I tried to come up with a little scheme to help me, but as of now it has only made more confusion... This is how my thoughts went. I know from quantum mechanics can one can relate classical...

Hello, To let you know where I stand, I am aware of the formal quantum theory (Hilbert space formulation). As you know, it states that an observable is an operator, and that's fine. My question is the following: what is the concrete realization of a measuring apparatus? The theory says...

Edit: Before posting in this thread, we'd like to ask readers to read three things: The https://www.physicsforums.com/showthread.php?t=414380". Don't forget the section on overly speculative posts. The paper http://arxiv.org/abs/1109.4897" The previous posts in this thread And...

Any examples of real-time energy measurement in homes? Hi :-) My professor told me that he thinks that if people are made more aware of the energy they consume in each action they perform (e.g the amt of electrical energy consumed by heating the stove for 15 mins..and such day to day...

Hams and Raedt gave a quantum computational algorithm to calculate the density of states of a spin system. Starting with an initial random state, they obtain the time evolution of the state. Later they take the inner product of the evolved state with the initial state. How does the inner...

Hi all, In our assignment, we were given this question: [PLAIN]http://img685.imageshack.us/img685/4854/prob213.png I know that for (a), the answer is the first energy eigenstate since the measured energy corresponds to it. I'm not sure about the situation in (b), though. Does...

Hi, In QM, when we make a measurement, our wavefunction collapses into one of the eigenstates of the operator. This process is supposed to be random for any single measurement but obeys some statistics if we make a large number of measurements. Could someone explain how we know that it is...

Hi, I think that this is (should be) a straight forward question: when conducting the double slit experiment, is there a relationship between the brightness / measure of the light source and the sum of the "peaks" from the interference pattern? (I have done a number of searches but can't find...

Does anyone know of a good textbook that would go in depth on current mirror circuits? What about methods and information on measuring low currents? My sedra and smith book does not talk anything about these subjects in detail.

How are ultra cold temperatures measured? For example, sometimes I see things measured in nanoKelvins. I'm thinking there has to be direct contact since the vacuum is already hotter than this, but how is it actually done?

Homework Statement i'm trying to find out how to model a system consisting of a body at a finite temperature, connected to a heat conducting rod that is lagged (see scanned image) and a thermometer (or any other temp measurement device), what would i take into account while modelling this...

Hi, I have deposited a film of dielectric on SiO2 substrate. Then, deposited metal dots on the top of dielectric film to measure electrical properties. I want to measure capacitance using metal dots on the top of dielectric. Since I have SiO2 as a substrate, I can not make a parallel plate...

Hi, I have deposited a film of dielectric on SiO2 substrate. Then, deposited metal dots on the top of dielectric film to measure electrical properties. I want to measure capacitance using metal dots on the top of dielectric. Since I have SiO2 as a substrate, I can not make a parallel...

Is it possible, practically or theoretically to measure the momentum of a quantum particle without altering the momentum? (the only real world tests I have read about involve collisions with other particles) If so, what would be result of a measurement of momentum have if interjected between...

Is conservation of energy, momentum, and other physical properties absolutely true in quantum mechanics, or only on average? As an example, think of a single particle in free space. Measure its energy, and write down the result. Then look at where it is, and measure the energy again. You'll...

I wondered how you can measure (static) pressure, with an as high as possible accuracy. Could you share your experience about which sensor and setup you allready used? I would like to measure the static pressure before and after a fan with an accuracy of 10[Pa]. Do you think this is possible?

What is the best way to hold it against multimeter sharp probes? The component is quite small and i want to avoid inaccurate result due to my hands holding it / placing it on the bench top

Hello, I wasn't sure exactly where to put this thread. Figured this was the most relevant section. Anyway, I wanted to know what exactly do meteorologists mean when they say that a region will receive 5mm or 10mm of rain during the evening. I read this wiki page...

This is actually a GRE problem, I'm just trying to go through and understand them all for studying purposes, but I don't understand how to do this one at all. Homework Statement A student makes 10 one-second measurements of the disintegration of a sample of long-lived radioactive isotope and...

I have two current signals from a two color Si-photodiode/PbS-photodetector. I want to measure the signal with the Stanford Research Lock-In Amplifier 830. I read in the manual that I can measure currents with the SR830. Does anyone have experience with this? Do I get better signals if I...

Hello In an electron diffraction experiment usually the diffraction rings are blurred. My question. If measuring the diameter, should I measure to the inside of the ring, the outside, or take a guess where the middle of the ring is and measure to there? Thanks

hey, could someone tell me if it is possible to measure the angle of twist of a rigid shaft subjected to a torsional moment at one end by using eddy current testing?

To calculate the height of a crane which is on top of a building, dennis measures the angle of elevation to the bottom and the top of the crane. these were 62 degrees and 68 degrees respectively. if the building is 42 metres high find the height of the crane. I'm asking for a friend, excuse the...

Weak measurement show that you can get "partial/probabilistic" which-way info and get a "partial" interference pattern. Deduction 1: Does this mean that weak measurements prove that we can control the degree of randomness? (either of individual photons or average of a thousands of photons)...

Does it explain what occur during strong measurement or "approximately" solve the measurement problem? I'm asking because below it is mentioned that "it is this uncertainty that creates the uncontrollable, irreversible disturbance associated with measurement". Does it mean that measurement...

Hello Rockwell B or Rockwell E - which one is better to measure the hardness of aluminum alloys? Thank you!

I'm working on a high power multi-phase DC/DC converter where the load current has some fast transients. We can easily measure the output voltage in the time domain, and also measure the power distribution network impedance in the frequency domain. So, I think I would try converting the...

I pasted a paragraph from http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-845-quantum-complexity-theory-fall-2010/lecture-notes/MIT6_845F10_lec02.pdf" below. ------------------------------ Consider the following matrix which represents a 45◦ counter clock wise...

Does anybody else besides Fra believe that quantum mechanics' Measurement Problem, Quantum Gravity, and Unification Program of all Forces are somehow related? Why and why not (pls. state or elaborate why you think or don't think so)?

Hello I want to measure the lateral acceleration at the center of gravity of a vehicle. I cannot place the accelerometer here since I cannot mount it properly so I have placed it 75 cm to the left of the CG. The longitudinal and and vertical placement is approximately correct. It there som...

Hi We are measuring 3 Phase Power of an asynchronous Motor-Generator and have equipment installed on Phase 1 (L1) and Phase 3 (L3) to measure the current/voltage/power. I have some questions regarding the results. Q) Why is the Power of Phase 1 positive and Phase 3 Negative ? Q) How can...

Hi, there. I am not major in physics so maybe I lack some basic knowledge. Imagine one have an ideal sensor, which can convert the emission to some kinds of signal (typically, voltage), then what process can describe the measure data? Is it related to...

Hi everybody! Would someone please advise on the following matter. I'm making up a table of railcar operating loads. One of the column includes abbreviated units of measurement such as kN, MN, N/mm2, etc. The question is: How should I title the column? I was thinking about titling it...

In Quantum Mechanics, there are measurement problems and you have many interpretations like Copenhagen, Many Worlds, de Broglie/Bohm mechanics, etc. Are there also measurement problems in Einstein Special Relativity for instance? Can't we consider the following: Spacetime in Relativity is...

The roentgen (R, also röntgen) is a unit of measurement for exposure to ionizing radiation (such as X-ray and gamma rays), and is named after the German physicist Wilhelm Röntgen. Adopted in 1928[1], 1 R is the amount of radiation required to liberate positive and negative charges of one...

how is time measured? if time is 1 sec distance traveled by light is 3 lakh km for that time is "c" now if we overcome this speed we have to go into future,but the problem here is we take light as a reference,had we not taken light as a reference in measurement of time,there would have been no...

Transmission line charateristics measurement?? Dear all, I want to do cable analysis of a 3800m long twisted pair wire to set up a communication system. It is not usual twisted pair wire (telephone), has different impedance, R=194, L=4mH, C=180uF. The things to be analyzed are...

I am thinking of using the output frequency of a 555 relaxation oscillator for measurement purposes. The frequency would be related to my measurement signal. How stable are these oscillators at low frequencies? Any personal experiences would help. How stable can you get then with good...

It is mentioned in the book "Quantum: Einstein, Bohr and the Great Debate about the Nature of Reality" the following: "Once the momentum of particle A is measured, it is possible to predict accurately the result of a similar measurement of the momentum of particle B as outlined by EPR...

Homework Statement according to the measurement postulate of quantum mechanics what happens if Q-hat is measured, followed immediately by a measurement of a compatible quantity R-hat and then a further measurement of Q-hat? you may assume that the eigenvalues of Q-hat and the eigenvalue of...

Hello Everyone, My statistics is terribly rusty so I am turning to all of you for assistance! I am in the process of reviewing my old text but I figured this may be quite a bit quicker. Homework Statement Suppose "x" is normally distributed with "mu_1" and "sigma_1." Now suppose x is measured...

There are lots of for metal cutting measurement. However, thermocouple is not in the list of metal cutting measurement. Anyway, is it possible to measure the temperature for turning machine by using K-type thermocouple. Can i put the thermocouple at the end of cutting edge to measure ? can it...

Hi everyone, How do u measure temperature, let's say of a car bulb without using a thermometer? Your ideas are all welcomed. Thanx

I am going to use tool work thermocouple to measure the temperature but i am facing a problem. I know i can use steel strip to one of the wire. but how about the second wire? If my insert is Titanium Carbide. Is it ok if i using different material from the insert to connect to second wire ...

How do flux meters work ?? On what basis they measure the strength of field please share the link (Urgently required)

Question Suppose molecules are placed next to the slits that fluoresce when electron passes, emitting a photon that can be imaged. Explain why this is no better than direct illumination, and explain how the two-slit interference pattern is destroyed. My Answer In direct illumination, a...