0
votes
0answers
2 views

Are there any issues connecting Neutral and Live at once to the supply line?

This is related to electrical engineering. A normal plug point has the wiring structure of the normal cct diagram I've drawn below. I'm thinking about plugging a device into the outlet in a permanent ...
0
votes
1answer
38 views
+50

What determines a particles probability of creation?

I know when we're discussing events at a quantum level, we deal in probability and not absolutes. What I'm looking to understand, is when articles I've read on particle physics state a particle has a ...
0
votes
0answers
1 view

Constant RPM of Gas Compressor

I would like to clear out my understanding of gas compressor. If it is moving at constant RPM, is it mean that it can only allow same volumetric flow rate all the time? So the power will remain ...
4
votes
1answer
694 views

What is the definition of particle-hole symmetry in condensed matter physics?

People often talk about particle-hole symmetry in solid state physics. What are the exact definition and physics picture of particle-hole symmetry? How to define the density of particles and holes?
1
vote
1answer
68 views

Difference of connections in the Killing vector equation

For the Killing vector equation, I sometimes see it written in terms of spin connection $\omega$ and other times in terms of the affine connection $\Gamma$. What is the difference between the two ...
2
votes
1answer
94 views

Gravitational potential in GR

In proving that the metric will play the role of gravitational potential, there is this chain of ideas: ...
0
votes
2answers
88 views

What experience tells us that gravitational acceleration cannot vanish everywhere?

In attempt to describe the consequences of the Equivalence Principle: When there are gravitational accelerations present, as for example in the gravitational field of the earth, the space cannot be ...
1
vote
1answer
95 views

Solve unsteady state Bernoulli equation for flow in a pipe

I am an engineer studying an unsteady-state flow through a pipe. The Pipeline has been cleanly cut into two halves, without deforming the cylindrical form of the pipe, exposing the contents to ...
0
votes
0answers
16 views

Why the rear wheels of vehicle is a bit larger than the front ones? [on hold]

for example, I have found it in a tractor and racing car. Is it for getting more rectilinear speed for same angular speed?
1
vote
1answer
123 views

Scale invariance in QFT?

About scale invariance in "beyond the standard model". At the base of the analysis is the principle of scale invariance. So what is being said: what if there were another sector of the theory that ...
0
votes
1answer
14 views

How will the Milky Way / Andromeda combined galaxy appear in 4 billion years?

In 4 billion years, do we we have an idea of what the combined Milky Way and Andromeda galaxy pairing will look like? In particular, will the presumed black hole at the centre of our galaxy, (and I ...
2
votes
1answer
48 views

Newtonian motion of a particle confined to a smooth surface

Recently, I've been considering a model wherein a lone particle with constant mass m is confined to a surface $F$: $\mathbb{R}^m \to \mathbb{R}^n$ , where $m < n$. I declare this surface to be ...
4
votes
1answer
252 views

Time-dependent Schrodinger equation from variational principle

In the paper, "Density-functional theory for time-dependent systems" Physical Review Letters 52 (12): 997 the authors mentioned that the action $$ A= \int_{t_0}^{t_1} dt \langle \Phi(t) | i ...
0
votes
0answers
52 views

Relativistic Fermi Golden Rule?

On online slide notes, it is mentioned that: Fermi Golden Rule: $$P_{if}=\frac{2\pi}{\hbar}|M_{if}|^2\rho_f$$ where $\rho_f$ is density of final sates --number of quantum states per unit volume - ...
3
votes
3answers
480 views

Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
1
vote
0answers
21 views
+50

Given a VEV how can I compute which generators remain unbroken using tensor methods?

This is a follow up to this question. A generator $T_a$ of a given gauge group $G$ remains unbroken after some Higgs field $\Phi$ gets a vev if $$ T_a \langle\Phi\rangle =0 $$ I'm trying to ...
0
votes
0answers
7 views

Question about spin-resolved current

I would like to ask you about the definition of spin-revolved current? Is it the spin current ? Thank you a lot.
1
vote
3answers
521 views

Neutrinos have mass. But how much mass?

Can somebody explain to me how much mass neutrinos have. According to my understanding neutrinos oscillate, therefore they should have some mass. If this is right then how much mass do they have?
3
votes
1answer
31 views

Would Michelson-Morkey experiment measure wind in non-vacuum?

If we derive the speed of light from the Maxwell equations we will find it's a function of the permittivity and permeability of the medium. Now let's play with the thought that we are living in a ...
0
votes
0answers
4 views

Calculating cost of producing cryogenic liquids

Using most efficient equipments, how much energy we need to produce one liter liquid nitrogen and how many joules for liquid helium? Is there a fixed equation to calculate how much liquefying each ...
0
votes
1answer
35 views

Time in general relativity

A physical quantity is introduced by its operational definition. In general relativity we use a differential manifold to describe the 4-dimensional space-time and, to identify a point in it, we use a ...
5
votes
5answers
491 views

What is the simplest possible experiment that proves that there are atoms? [duplicate]

As I known all the matter consists of atoms. What is the simplest possible experiment (with as little scientific equipment as possible) that can prove that there are atoms?
1
vote
1answer
148 views

Potential Energy of Springs and Gravity, and Work of a force

I am currently really stuck on this problem and I am not sure how to actually solve it, I think I can reason it out logically but I do not know how to show it. Here it is and under I will show what I ...
1
vote
5answers
551 views

Why is it easier to go uphill on a lower gear?

In cars as well as bicycles, when we are on a lower gear, the driving wheel (the one on the wheels) has a bigger radius compared to when on a higher gear. So on a lower gear the bike/car would move ...
2
votes
0answers
43 views
+50

Velocity profile of a viscously damped wave

For a test case, I want to determine the velocity profile of a viscously damped standing wave. By linearizing the density ($\rho=\rho_0+\rho'$) and velocity ($ux=ux'$), the continuity and ...
0
votes
1answer
61 views

What's Wrong With This Quantum Analogy?

"Sometimes the idea of the quantum is compared to the units we use for money. A dollar can be divided into smaller units, where the cent is the smallest possible unit." A question I came ...
0
votes
0answers
11 views

Boiling water function

i want to make a program that realistically boils water with all the variables but know near nothing about the math i got the energy transfer equation down but this seems to be giving me some ...
1
vote
1answer
30 views

For infinitesimal Canonical Transformations, what functions are allowed for this to be a canonical transformation?

Consider two infinitesimal transformation: $$q_{i} \rightarrow Q_{i} =q_{i} + \alpha F_{i}(q,p) $$ $$p_{i} \rightarrow P_{i} = p_{i} + \alpha E_{i}(q,p) $$ where $α$ is considered to be ...
2
votes
1answer
49 views

Einstein-Yang-Mills Connections

I am playing around with coupling a classical $SU(2)$ Yang-Mills theory to Einstein's equations. Assuming spherical symmetry, the $SU(2)$ connection can be written \begin{equation} A = ...
16
votes
1answer
589 views

Is an electron a superconductor?

A superconductor has zero resistance. What about an electron in a vacuum? Could this simple system be considered superconducting?
3
votes
2answers
186 views

How to use an accelerometer to correctly quantify the magnitude of vibrations

Consider the following setup: An accelerometer is placed inside a helicopter, measuring $g$ values along three axes $(x,y,z)$ every $10~\text{ms}$ (100 times a second), during a helicopter flight. ...
-1
votes
1answer
36 views

How can a two-state ammonia molecule have more than two states?

[...]this molecule, like any other, has an infinite number of states. It can spin around any possible axis; it can be moving in any direction; it can be vibrating inside, and so on, and so on. It ...
0
votes
1answer
26 views

What is the difference between the magnetic-field of a Permanent-Magnet and that of an Elecgtromagnet

What is the difference between the magnetic-field of a Permanent-Magnet, and that of an Electromagnet ? In the diagram below, you can see that the 'magnetic-field' of an ...
2
votes
3answers
2k views

Artificial planetary magnetic field

I wonder how difficult it is to create an artificial planetary magnetic field with generators? What power they would need? The question is inspired by thinking about possible colonization of ...
2
votes
1answer
109 views

Which way to lean when driving a gokart?

Given a car that has two lines of wheels, the center of gravity at constant height above the ground, constant turn angle and given surface and wheel material. What is the maximum speed the car can ...
0
votes
3answers
442 views

Are there any non dissipative-non conservative forces?

Although the question stands for itself, I would like to know that if the answer has to be no then does any particular law forbids the existence of such forces; and if there are such forces then what ...
0
votes
0answers
12 views

Help understanding Diamagnetism in external field

Lorentz force can not do work. Therefore it can not change the velocity of electron. Then how do you explain diamagnetism in terms of speed of a pair of electrons in the orbit?
-1
votes
0answers
8 views

Alternated current and EMF

Can peak value of ac greater than ac voltage? I think this question is clear. What would be the value of peak voltage if the resistor is less than one?
2
votes
2answers
167 views
+100

Showing that a mass moves a half cycle

Consider a mass $m$ at position $x(t)$ on a rough horizontal table attached to the origin by a spring with constant $k$ (restoring force $-kx$) and with a dry friction force $f$ $$\begin{cases} ...
0
votes
1answer
112 views

Induced Current & Lenz's Law - 2 Circular Loops with same direction of current

I'm new to the wonderful world of physics, and I'm really confused about magnetism and induced currents. Let's say we have 2 circular closed loops that each carry a current $I$ clockwise and the ...
0
votes
0answers
12 views

Find the angle when lower mass loses contact with ground

Consider the following simplified model of a skater falling over: Two equal masses $m$ are attached to opposite ends of a light, straight rod of length 2. One mass rests at $(0,0)$ on a ...
0
votes
2answers
91 views

Forces Create Angular Acceleration And “Straight” Acceleration - But How Much Of Each?

Let me set up the following problem for a rectangle floating in space: We know its dimensions. We know its mass. There's a force pushing it for a known amount of time - we know the angle & ...
-2
votes
1answer
50 views

Quantum Gravity [on hold]

By the Pauli exclusion principle fermions cannot occupy the same space, cannot have identical quantum numbers. The bosons however can. We also know that the universe, and in particular the various ...
0
votes
1answer
23 views

Increase of an electron's (relativistic) mass

Considering the equivalence of mass and energy, is we want to increase the (relativistic) mass of an electron 1000 times, should we give it 5*10^5 * 1000 = 5*10^8 eV of Kinetic energy => 1001 electron ...
1
vote
2answers
300 views

A student of mine wants to build a gyroscopic inertial thruster

I work as a tutor with students in their first three semesters. One of my more eager students is obsessed with the gyroscopic inertial thruster . Here is a Wikipedia article on it. I was not able to ...
6
votes
1answer
3k views

Why, when one opens 1 car window, does that noise occur?

When you're driving and you open 1 car window, say the front one, there comes a horrible noise, but when you open another window just the slightest bit, this noise goes away (I'm sure most people know ...
-1
votes
0answers
21 views

How does gravity and velocity affect the time we see on our watches?

I had heard about the fact that the gravity we experience makes a difference in the time in our watches and also our velocity when it is close to c (speed of light). Can anyone please elucidate how it ...
-1
votes
1answer
16 views

Potential difference in a circuit of n cells = 0? How?

I was supposed to find the potential difference across any one cell in an arrangement consisting of n cells of EMF E connected in series in a closed circuit and internal resistance r. I proceeded by ...
1
vote
1answer
40 views

Why is there an energy gap in superconductors?

I'm a little out of my depth here... I'm trying to understand quasiparticle tunnelling in superconductor-insulator-superconductor junctions. Many books use the "semiconductor model" to explain this: ...
-2
votes
0answers
10 views

magnetic field of bar magnet

two bar magnet each of magnetic moment M are hang through mid point of each. such that both are perpendicular to each other . find the magnetic field at the line which is angle bisector of the two ...

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