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Questions tagged [measurements]

The tag has no usage guidance.

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119 views

A theoretical limit of accuracy?

Is there an agreed upon/conjectured theoretical limit to our ability to resolve the accuracy of time?
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0answers
23 views

Would the voltmeters give different readings in a circuit with induced current?

$\def\vE{{\vec{E}}}$ $\def\vD{{\vec{D}}}$ $\def\vB{{\vec{B}}}$ $\def\vJ{{\vec{J}}}$ $\def\vr{{\vec{r}}}$ $\def\vA{{\vec{A}}}$ $\def\vH{{\vec{H}}}$ $\def\ddt{\frac{d}{dt}}$ $\def\rot{\operatorname{rot}}...
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1answer
29 views

Least count of Vernier

Is least count not always 1 main scale divsion-1vernier scale divsion or is it always least reading possible on main scale/ no of vernier divsions. question: 1 main scale reading be 1 mm Lets say 5 ...
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1answer
26 views

The difference in using a predetermined error or standard deviation for calculations

Please edit the thread's tags and content if there are mistakes. I am not sure where If I'm posting my question with the right tags. This is a simple question regarding the study of Linear Motion by ...
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0answers
48 views

Spacetime curvature and measurements

From a programming perspective, I've always thought of gravitational influence as a kind of vector field, (crudely drawn) which seems to attribute to the motions of bodies through the field ...
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1answer
66 views

Are there ways to detect/measure photons that don't involve electrons?

As per question, are there ways to detect photons, and/or to measure their energy, that don't involve any interaction with electrons? And if yes, are there detectors which use photon interactions with ...
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1answer
18 views

Convert negative parameters of Altitude Height into possitive using BMP180 Sensor

I am using BMP180 I2C sensor interface with Arduino and with the help of mentioned below code ...
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0answers
74 views

How do we quantify and measure the net entropy of today's universe?

We know that the Universe evolved from a very low entropy state in the early universe to very high entropy state of today's universe. What is the quantitative definition of the net entropy of the ...
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2answers
28 views

Would equipment that is wrongly used by a person be considered as a systematic error?

Would equipment that is wrongly used by a person be considered as a systematic error or a random or both? I would say a systematic error because a person could don't know how to use a ruler and starts ...
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2answers
96 views

Perfectly distinguishable states are mutually orthogonal

$\newcommand{\bra}[1]{\left<#1\right|}\newcommand{\ket}[1]{\left|#1\right>}\newcommand{\bk}[2]{\left<#1\middle|#2\right>}$ Let $H$ be a Hilbert space. We call states $\ket{\psi_1}, \...
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3answers
47 views

Uncertainty in ripetitive measurements

Good afternoon everyone, I have a question which is puzzling me and I did not found an acceptable answer yet. Suppose you have acquired some data from a measurement and you have the following numbers: ...
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3answers
135 views

Why is physics taught as if measurement doesn't affect the thing being measured? [closed]

I've recently started my journey in understanding the math of quantum mechanics and I've noticed a strange pattern. (I'm not saying that the popular interpretation of quantum physics is wrong or ...
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1answer
27 views

How to determine whether an alloy is single or multi phase

I would like to know what methods would be suitable to determine if an alloy of 2 elements is a single phase or two phase alloy.
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2answers
38 views

Is there experimental evidence for the irreversibility of the collapse of the state of a system due to a measurement?

It has been pointed out by one of my professors that, in quantum mechanics, the collapse of the state of the system by measurement is not time-reversible, i.e once the system collapses due to a ...
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1answer
44 views

When the barometer drops, my well level seems to rise - how?

I have a deep water well, with a length of 1/4" drip tubing, open at the bottom, taped to the pump 180' down. The other end of the tubing is connected to a gauge pressure sensor in the cabinet of my ...
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0answers
8 views

Calculating Uncertainty with Mean Absolute Deviation

I'm taking an Introductory Physics course and, when learning about approximating uncertainty, I was wondering if a more quantitative method would be to calculate the Mean Absolute Deviation using the ...
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1answer
64 views

Heisenberg uncertainty principle meaning and using it to determine approximate sizes confusion

I was always under the impression that the Heisenberg uncertainty principle tells us to what precision we can make a momentum measurement given a position one. However, when doing quantum mechanics ...
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1answer
99 views

Reflection Vector (Ray Tracing)

Snell's law of refraction at the interface between 2 isotropic media is given by the equation: \begin{align} \tag{1} n_1 \,\text{sin} \,\theta_1 = n_2 \, \text{sin}\,\theta_2 \end{align} $\qquad$ ...
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0answers
26 views

Attempting to calculate the mobility from SCLC measurement (space charge limited current)

I performed an SCLC measurement on a p-type material (hole transport layer) for a solar cell. Referring to the wikipedia page:https://en.wikipedia.org/wiki/Space_charge The relationship between $J$ ...
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0answers
28 views

Can traps measure which path in an interferometer?

it is possible in an interferometer to block the paths with screens so that the particle is well located in one of the paths. I wonder if it is the same when instead of screen we use traps in which a ...
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1answer
84 views

Are there any physical quantities that are loglog?

Most units, e.g. for length, time, mass, etc, are linear in relation to the underlying property. But there are some special quantities, where the units can vary several orders of magnitude within the ...
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1answer
60 views

A delicate measurement?

The identity operation means that we are not disturbing the system at all. However, if we consider the following operation $$ \begin{pmatrix} 1 + \epsilon & 0\\ 0 & 1 + \...
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1answer
42 views

Experimental measurement of the radial excess

Update: I have updated the the question, see below. The radial excess due to the curvature of spacetime is a well-known prediction of General Relativity that is often mentioned in introductory texts, ...
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0answers
19 views

Porous nanostructure in TGA and DSC

How does the porosity in porous nanostructures, such as mesoporous silica, influence the observed response in Thermal Gravimetry Analysis (TGA) vs Differential scanning calorimetry (DSC) thermograms?
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1answer
44 views

Profile of a platinum-iridium meter bar

The former meter standard, platinum-iridium meter bar, had a specific cross section somewhat resembling mixed variant of letters "X" and "H" with serifs (Image source): What was the reasoning behind ...
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3answers
124 views

Shot noise in optics

There are many explanations to be found about shot noise in optics, but the answers I find are incompatible. There are three ways shot noise in optics is explained. (Note that according to ...
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2answers
79 views

Work definition does not make any sense for coherent states? TPM (two projective measurement) scheme

I'm talking about the relation that if we are in a isolated, quantum system that only allows for work exchange with the surrounding system we know from the first law of thermodynamics that $\Delta E = ...
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0answers
10 views

Can radio waves be detected using a coulomb torsion balance?

Radio waves are almost everywhere. shouldn't the coulomb torsion balance be sensitive to any passing through the device?
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1answer
124 views

How can a Lego version of a Kibble balance measure the Planck constant?

As the picture shows below [][1] in a Kibble balance, one can drop out the measurement uncertainty of $B$ (magnetic flux intensity) and $L$ (length of coil) by the use of two modes, force mode and ...
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1answer
47 views

Calculation of Thermometer Time Lag?

A couple of days ago, contributor 'Rogan Parks' posed the question below the page break. I was about to fully answer it when the OP for no apparent reason deleted his question. I find it an ...
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1answer
70 views

Why does my thought experiment involving entanglement appear to violate the speed of light?

I have a thought experiment that "seems" to allow messages passed at faster than the speed of light. Since that is impossible I'd like to learn what is wrong with my experiment/reasoning. Start with ...
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2answers
44 views

Relation Between Speed of Light & Reflected Angle (Fizeau–Foucault)

I have a bachelor's in physics & its recently struck me that I do not understand, semantically, what phenomenon allows us to measure the speed of light through air in a small room with a laser and ...
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1answer
64 views

Is a quantum channel essentially either a unitary evolution or a measurement?

I'd like to understand exactly what people mean when they speak of quantum channels. As I understand it, we can represent a channel by a set of Kraus operators, $M_i$, which satisfy $\sum_{i}M^{\...
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2answers
55 views

Relation between momentum and momentum uncertainty

I have read the following sentence in a section which is explaining why particle accelerators need such high energy: As we require high precision position measurement, the Heisenberg uncertainty ...
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1answer
36 views

How to write down the state after a measurement if the result was not recorded?

I measure the spin of an unknown qubit in the computational basis but I do not record what the outcome of the measurement was. How should I now describe the state? If it is described as a maximally ...
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1answer
198 views

A new definition of mass using Planck constant

Tonight in a italian television news channel well known internationally I have heard that almost certainly the definition of mass that we currently know will be obtained by means of the constant ...
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1answer
92 views

Is the uncertainty principle a circular argument? [closed]

Uncertainty is due to the measurement techniques humans tend to use requiring photoelectric effect. The Planck constant is due to the photoelectric effect. If the standard deviation of measurement was ...
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3answers
64 views

Is it possible to suggest a physical experiment in which measurement errors are dramatically increasing? (due to the accumulation of errors)

Is it possible to suggest a physical experiment in which measurement errors are dramatically increasing? (due to the accumulation of errors) Maybe some magnetic field can be used here? Or any other ...
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1answer
57 views

Nielsen and Chuang 2.2.3: state of a qubit after measurement

(Apologies for the poor typesetting of kets. I haven't been able to figure out how to do that on this site). On page 85 of Nielsen and Chuang's textbook, they write that the probability of obtaining ...
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1answer
70 views

Problem in measuring uncertainty

While performing an experiment involving a bar pendulum, we had to measure the time period of one oscillation by measuring the time taken for 30 oscillations. There is some confusion regarding ...
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1answer
22 views

Error of capacitnace measurement using a multimeter

physics stack exchange Many multimeters have a setting for measuring capacitance. The multimeter I have has a precision of four significant figures, or in other words, it returns the value in the ...
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1answer
37 views

How do multi-meters measure capacitance?

Many multimeters have the ability to measure capacitance along with the ability to measure AC voltage, DC voltage, current, resistance ... The only equations I am aware of that determine capacitance ...
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1answer
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Changing transmittivity of polarizing filters for different wavelengths

I suppose, that a polarizing filter works as described here: The polarizing filter absorbs or reflects some of the photons in the light beam, which is why the energy/power measured after the ...
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4answers
106 views

Difference between unpolarized beam and half H+V polarized beam

Let's say that we have got two light beams. Beam A is not polarized at all. Beam B is composed of half H polarized photons + half V polarized photons. Is there any way to measure those two beams in ...
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2answers
52 views

Is a quantum gate different from taking a measurement?

I'm reading a book on quantum computing. It is a very non-technical book, and I do not need a very technical explanation. I keep on seeing the words quantum gate pop up, and I'm wondering whether this ...
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1answer
127 views

Heisenberg choice of the observables and different outcomes [duplicate]

Somebody could help me to clarify how its possible that different choices of the observable to measure can lead to different outcomes of the observed system state?
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1answer
46 views

How to measure width of a very narrow spectral peak without expensive instruments?

Lasers typically have very narrow peaks in their spectrum, much narrower than 1 nm. It would require quite a high-resolution spectrometer to measure such a peak precisely. But if I simply need to find ...
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1answer
42 views

Strain gauge vs linear variable displacement transducer

For measuring deformation experiments, it seems that strain gauges and linear variable displacement transducers (LVDT) are commonly used. If the material exhibits geometric linearity, then couldn't we ...
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6answers
1k views

Are uncertainties higher than measured values realistic?

Whenever I measure a positive quantity (e.g. a volume) there is some uncertainty related to the measurement. The uncertainty will usually be quite low, e.g. lower than 10%, depending on the equipment. ...
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1answer
67 views

Measure temperature of a heater wire

I would like to measure the temperature of a heating wire (tungsten) that's wrapped around my sample. Does anyone have a better idea than using a infrared thermometer, which has relatively low ...