0
votes
0answers
14 views

Does a cathode ray tube emits electromagnetic waves from a steady DC electron beam?

In cathode ray tube, heated cathode emits stream of electrons but when I wrap a coil around tube a current will be inducted in that coil? after all electron beam is a steady DC current? so no emf?
-5
votes
0answers
8 views

Characteristics of EMF [on hold]

EMF Characteristics of Chemical,Magnetic,friction,Piezoelectric,Photoelectric and Thermocouple also advantages and disadvantages and used for.
0
votes
0answers
20 views

Why is weak hypercharge not a function of the number of up or down quarks?

I'm fairly new to quantum mechanics, and I was looking up some basic information about the weak force and it's interactions. I found this equation of weak hypercharge on Wikipedia and quoted a few ...
6
votes
1answer
879 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?
3
votes
3answers
6k views

What is displacement? Position relative to a reference point or change of position

What is the "official" or most useful definition of displacement in the context of kinematics? There are two common ones: Displacement is the length and direction of a line from a fixed reference ...
0
votes
0answers
10 views

What is $\beta^-n$ decay?

I'm looking on the nndc chart of nuclides and am seeing $\beta^-n$. What is this? http://www.nndc.bnl.gov/chart/reCenter.jsp?z=3&n=6
2
votes
2answers
26 views

How can an electron's magnetic moment precess around the direction of an external magnetic field?

I am reading this article: The Nature of the Electron by Don Lincoln in The Physics Teacher, Volume 54 (2016), pg. 203, and I ran across the part where he talks about measuring the magnetic moment of ...
-1
votes
0answers
34 views

Are we approaching Bremermann's Limit, or running from it? [on hold]

Is computational density increasing, or decreasing? Or, more generally, is the computational density of a given region of space know to strictly to increase with time? (Is it linked with entropy and ...
1
vote
0answers
56 views

Is it possible to determine maximum frequency of a disc using a relative circumference?

On Wikipedia there is an article that shows how to calculate the relativistic effects on a rigid spinning disc, I am referencing the formula under the "Ehrenfest's argument" section in the link. The ...
-2
votes
1answer
24 views

Mass and spin relation [on hold]

Wich is the relation between mass and spin? If I have a particle that is formed by the quarks $ud^{*}$, if its spin is $0$, the mass of this particle will be smaller than the mass of the particle ...
1
vote
2answers
52 views

Work done according to Newton's Principia

Actually I was going through the principia, reading Newton's derivations of the properties of ellipses. Suddenly I had this question which got stuck in my mind - Throughout Principia Newton uses the ...
4
votes
1answer
313 views

Off-diagonal elements of Hamiltonian matrix $H_{12}$ & $H_{21}$: energy of transition from $|1\rangle$ to $|2\rangle$ or amplitude of transition?

$$ \newcommand{\k}[1]{\left| #1 \right\rangle} \newcommand{\dd}[1]{\frac{d #1}{dt}} $$ In a Hamiltonian Matrix like this: $$H = \begin{pmatrix} E_{11} & E_{12} \\ E_{21} & E_{22} ...
0
votes
0answers
32 views

Relationship between Unitary rotation and projectors in Proof for relation between principal angles using Jordan's Lemma

I am trying to understand the proof of the following theorem, given in Fast amplification of QMA: We want to first establish some relations which will be needed to understand the following theorem ...
0
votes
0answers
12 views

finding the plane of cleavage in crystals

The crystal can be clear such as diamond or shiny like germanium or metallic like galena or fools gold. I would like to cut some of these cleanly along natural cleavage lines. I would also like to ...
0
votes
1answer
28 views

Fermi-Dirac distribution - holes and electrons

The density of probability of an energy state $E$ being occupied by an electron is $$f(E,T)=\frac{1}{1+e^{\frac{E-E_F}{kT}}}$$ and the density of probability of an energy state being occupied by a ...
0
votes
0answers
23 views

Solving ODE with essential singularity [migrated]

I would like to solve the following linear ODE. $y''(x) -\frac{2}{x} \frac{1-3x^4 +2x^3}{1+3x^4-4x^3} y'(x)+\frac{\omega^2}{(1+3x^4-4x^3)^2} y(x) = 0$ Here $x$ is a dimensionless variable which runs ...
0
votes
0answers
13 views

Is the self-interaction mass of a geon related to the mass gap?

I wrote in the question about how type II and III solution have longitudinal components and are related to a geon. This mass has a similarity to the mass gap in gauge theories. In light of the ...
0
votes
0answers
12 views

Query about Ramond-Ramond fluxes associated with a Dp-brane

A paragraph in the string theory book by Ibanez and Uranga (String Theory and Particle Physics by Luis Ibáñez and Angel Uranga) has confused me. According to the book (for a screenshot of the ...
-1
votes
2answers
51 views

Force at the centre of gravity [on hold]

If we somehow apply a force direct to the center of gravity (existing inside an object ) , does it increase the angular velocity of a rotating object as it does in normal case ?
6
votes
1answer
222 views

Is there a physical interpretation to invariant random matrix ensembles?

Disclaimer. I am a graduate student in pure mathematics, so my knowledge of physics more advanced than basic 1st/2nd year undergraduate physics is very limited. I welcome corrections on any ...
0
votes
2answers
19 views

Centrifugal force acting on Spacecraft

This Question may sound very naive. Still somebody can explain the basics in simple words. As I understand, when we equate the centrifugal force acting on spacecraft in circular orbit with ...
12
votes
1answer
409 views

How do I enforce the no-slip boundary condition in time dependent incompressible pipe flow?

This is a technical problem which must have been solved already. It won't be in beginners textbooks but there should be a solution somewhere. I welcome reading suggestions. Maybe someone with ...
13
votes
1answer
463 views

Introduction to neutron star physics

I enjoy thinking about theoretical astrophysics because I want to understand black holes. Given that no one understands black holes, I like to ponder the nearest thing to a black hole: a neutron star! ...
2
votes
3answers
299 views

What is the relationship between rolling resistance and velocity?

I'm a games programmer, trying to write a simple car physics simulation. I'm aware that a car travelling in a straight line will exert a traction force that drives it forwards (by turning the wheels ...
2
votes
1answer
52 views

Will the speed of gravity and the speed of light always be the same?

I have been considering the following though experiment: If the entire sun were to disappear at once, would we feel it first due to the sudden drop in gravity or see it first? The answer I have come ...
-2
votes
0answers
34 views

Can someone explain me magnetic potential?

I don't understand why we can write the magnetic field as a potential vector A, and what exactly this potential is. Is it just a mathematical thing? And how can it help me calculate the magnetic ...
0
votes
0answers
22 views

Partial Differentiation without chain rule in Euler Lagrange Equations [duplicate]

The Euler-Lagrange equations for a bob attached to a spring are $$ \frac{\mathrm{d}}{\mathrm{d}t}\frac{\partial L}{\partial v} = \frac{\partial L}{\partial x} $$ But $v$ is a function of $x$. Is it ...
0
votes
3answers
23 views

Heat transfer equally distributed?

When heat is introduced to a copper bar's end surfaces(right or left surface) of a certain volume $cm^3$, is the heat uniformly distributed? In my calculations of heat transfer, I'm using $$Q = mC_P ...
0
votes
0answers
25 views

Derivation of Lagrangian [duplicate]

Actually I am beginning to study Lagrangian and Hamiltonian Mechanics. The book that I am considering directly introduces the Lagrangian L=T-V. Though further on the book , the Euler Lagrange ...
0
votes
1answer
23 views

If we actually conducted a twin paradox experiment using a rocket launched from earth

Does the equivalent acceleration / deceleration required to reach whatever speed then come back and rest in the original frame of reference zero out the time dilation effects for each party? So if we ...
1
vote
1answer
142 views

Energy conservation of permanent magnets engine

How to explain the fact that magnet can attract an object (apply a work W) without losing a (significant) part of its internal energy? How to apply the energy conservation principle? Please think to ...
3
votes
0answers
19 views

How are boundary consitions implemented correctly in time dependent hydrodynamics?

I posted this question more than one year ago and got an answer recently. This answer looks good to me, but indicates that something is wrong in my original approach to the problem. Can someone tell ...
-3
votes
1answer
32 views

How much force does a dog exert walking? [on hold]

When the average dog is walking, how much force does it exert based on the back-and-forth movement of its paws? How much force does it exert with the tip of its tail? Note: I may be posting this ...
0
votes
1answer
36 views

Impulse of two different objects

I was running over a question, A collision occurs between particles A and B which are moving in opposite directions in the same straight line. The impulse on each particle in the collision is 2N.s, ...
0
votes
0answers
62 views

Cavendish Experiment [on hold]

Would the earth’s gravity overpower the gravity of the much smaller and less dense lead spheres?
26
votes
5answers
4k views

Interpretation of “transition rate” in Fermi's golden rule

This is a question I asked myself a couple of years back, and which a student recently reminded me of. My off-the-cuff answer is wrong, and whilst I can make some hand-waving responses I'd like a ...
14
votes
3answers
2k views

Does Heat Cause Time Dilation?

Since heat is defined as the movement of molecules, and because of relativity time slows for faster moving objects, would a hot object be in a slower time frame then a cooler object, because the hot ...
0
votes
0answers
11 views

crystal lattice modification

Can the lattice of a copper with FCC structure be altered, even microscopically? Copper has 0.361 nm lattice constant but can it be altered by external force, say neutron impact?
2
votes
3answers
605 views

Proper time for an accelerating object

As far as I have read so far, proper time is the time measured on the clock of an inertial frame moving uniformly with respect to another inertial frame. The concept and the mathematical expression ...
0
votes
2answers
35 views

Carnot engine basics?

A line in my textbook says.. ' if we employ any other process that is not adiabatic, say an isochoric process, to take the system from one temperature to another, we shall need a series of ...
0
votes
0answers
3 views

Can I approximate the emission line FWHM for an etalon through doppler broadening?

I'm asked to find the finesse for an etalon needed to make the Zeeman effect of the red Cd line measurable. I found the Zeeman separation of the lines to be about $7 GHz$ for the apparatus given. I ...
6
votes
1answer
69 views

How can quantum tunnelling lead to spontaneous decay?

I have never understood what measuring process (if any) is supposed to be continuously polling the quantum state of an unstable bound system subjected to decay via quantum tunnelling. The reason I ...
2
votes
2answers
163 views

Balancing forces on a liquid [closed]

My reasoning is as follows Atmospheric pressure = $P_{0}$; Spring stretch = $x$; Pressure under top piston = $P$ Balancing forces on top piston $kx + P S_1 = P_0 S_1$ Balancing forces on bottom ...
1
vote
1answer
185 views

Rotation motion like the number 8

I'm a college student majoring in culinology and I'm trying to find out the reason or method of the number 8 motion. Responses doesn't have to be in culinology examples, but that would be a great help ...
31
votes
7answers
5k views

Supergun Launching of Satellites

I should say first that I don't believe this is a feasible launch method, otherwise NASA and other space agencies would be using it by now. It's based on this BBC news story Saddam Hussein's Supergun ...
7
votes
4answers
728 views

Is it true that the Schrödinger equation only applies to spin-1/2 particles?

I recently came across a claim that the Schrödinger equation only describes spin-1/2 particles. Is this true? I realize that the question may be ill-posed as some would consider the general ...
42
votes
5answers
3k views

What causes this pattern of sunlight reflected off a table leg?

My friend noticed an interference-like pattern around the table leg. However, we do know that interference patterns of sunlight produces rainbow colours. What seems to be happening here?
0
votes
0answers
16 views

Implication of breakdown of scale invariance for problems with intrinsic length or time scales?

According to Wikipedia article on scale invarince, the equations for electric (and magnetic) fields : $$\nabla^2\vec{E}=\frac{1}{c^2}\frac{\partial^2\vec{E}}{\partial ...
0
votes
0answers
14 views

Commuting of the covariant derivative: Menzel's Mathematical Physics

Menzel defines covariant differentiation as equivalent to partial differentiation with respect to the general coordinates. “To indicate the covariant nature of the differential operator, set ...
3
votes
2answers
48 views

Why cannot a fundamental string couple to the R-R gauge field $C_{\mu\nu}$?

People usually say that D-branes can carry R-R charges, or can couple to R-R sector gauge fields. But why a fundamental string cannot couple to a 2-form R-R sector gauge field? What's the essential ...

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