All Questions

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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?
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Characteristics of EMF [on hold]

EMF Characteristics of Chemical,Magnetic,friction,Piezoelectric,Photoelectric and Thermocouple also advantages and disadvantages and used for.
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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 ...
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?
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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 ...
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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
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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 ...
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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 ...
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 ...
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 ...
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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 ...
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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 ...
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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 ...
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 ...
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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 ...
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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 ...
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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, ...
62 views

Cavendish Experiment [on hold]

Would the earth’s gravity overpower the gravity of the much smaller and less dense lead spheres?
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 ...
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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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 ...
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 ...
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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 ...
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?
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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 ...