0
votes
1answer
42 views

Has someone measured that in the far field of radio waves, the electric and magnetic field oscillate synchronously?

That in near field both fields oscillating 90° displaced is obvious since in antenna rod a lot of electrons will be accelerated and and this oscillation of electric field is escorted by alignment of ...
0
votes
1answer
25 views

Why does the Magnetic Flux Density B, saturates in a ferromagnetic material with increasing H?

I understand that the magnetization must saturate as more and more domains are aligned. But $B$ is still directly proportional to $H$, and hence it must increase linearly with $H$. But every book ...
2
votes
2answers
25 views

Resulting force when bending plywood

My sister and I are working on a thesis in interior design on a plywood chair similar to the picture, where the red part bends. We are trying to work out how much the plywood would push back when a ...
0
votes
1answer
26 views

Determine normal forces on tilted table [on hold]

A table with the mass m, the height a and the width b is resting on a tilted floor with the angle of rake $\alpha$. A block at A prevents the table from sliding. Determine the normal forces from the ...
1
vote
0answers
16 views

Gamma matrices in Decay Calculations

I am trying to calculate the transition amplitude, $\lvert M^2\rvert$, for the process where a top quark (momentum p) decays to a bottom quark (momentum q) and a $W^+$ boson (momentum k). I am ...
1
vote
3answers
33 views

The speed of air rising through a heated tube

I would like to get an explanations of an observed physical phenomena. When a metal tube is placed vertically and heated and the air inside rises, the speed of the air moving through the tube ...
0
votes
1answer
63 views

Why is there zero point energy at absolute zero temperature? [on hold]

If we define the absolute zero as a temperature which there is no entropy in it so why should we have zero point energy?
0
votes
2answers
24 views

How can I calculate the partial trace for a combined state of a pair of two-level atoms to get a reduced state?

Let's say I have a combined state of a pair of two-level atoms, $A$ and $B$, given by the density matrix: $$ \rho = \frac{1}{2}\mid g_A, g_B \rangle \langle g_A, g_B\mid + \frac{1}{2} \mid g_A, e_B ...
0
votes
0answers
14 views

The angle of incidence of prism if emergent angle is 90°. Answer in terms of angle of prism and refractive index of prism [on hold]

A ray of light is incident at an angle of incidence i on one face of a prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is n, ...
0
votes
3answers
25 views

Path followed by a free test charge in an electric field region represent the electric lines of forces?

As we know that if we put any free test charge in an electric field which is moving horizontally then it will experience an repulsive force and move in that direction so by that we can say that for ...
0
votes
0answers
14 views

How can a string “shield” a tear in a flop transition? Can our expanded dimensions tear?

I have read recently that in a process called flop transition in calabi yau dimensions space actually tears and is then somehow "fixed" to create a new shape of Calabi Yau dimension. If a string wraps ...
2
votes
2answers
146 views

Why do electric field lines start and end at 90 degree at the surface of a conductor? [duplicate]

There is one property of electric lines of forces which states that: Electric field lines start and end at 90 degree at the surface of the conductor. But why is that so? Is there any proof for ...
2
votes
1answer
47 views

Pinhole Camera Problem!

I was reading slides of a university course and in one of the slides it says 1 Eyes/cameras can’t have VERY small holes because that limits the amount of entering light 2 and diffracts/bends ...
0
votes
3answers
47 views

Negative density solutions of the Poisson's Equation for polytropic gas (aka Lane-Emden Equation)

Question: What does it mean by when we obtain negative density for specific region in space as a solution of Poisson's equations? I will explain the situation as detailed as possible, so that anyone ...
2
votes
2answers
36 views

Work done by frictional force on a sliding block

A block slides across a table horizontally with an initial velocity $V$. The frictional force $F$ brings it to rest after its Centre of Mass covers distance $S$. What is the work done by the ...
-15
votes
2answers
105 views

When will physics understand it is the 'dark mass' not the 'dark matter'? [on hold]

There is new thinking occurring in physics where 'dark matter' is considered to be incorrect. The new thinking is that mass fills 'empty' space. The mass which fill's 'empty' space is being referred ...
0
votes
1answer
29 views

What would be the Slater's determinant representation for an excited state?

Setup Introducing this spinorbital notation: \begin{align} \Psi_1=\chi_{(r1)}\alpha_{(\omega1)} = 1 \\ \Psi_1=\chi_{(r1)}\beta_{(\omega1)} = \bar{1} \end{align} and the Slater's determinant, for ...
0
votes
0answers
15 views

What is the connection between Bragg's condition with reduced EK diagram?

In my course notes the professor mentioned that there was some relationship between the Bragg's condition and the first Bernoulli zone of the reduced EK diagram. Specifically, the boundary before ...
0
votes
3answers
62 views

Levi-Civita symbol and Hermitian conjugate

When we take the Hermitian conjugate/dagger of an operator expression which contains a Levi-Civita symbol, do we need to transpose the Levi-Civita symbol? E.g., for the crossproduct ...
-1
votes
1answer
38 views

Free-Falling Object

How does the presence of air affect the rate at which a body falls? What is the rule for falling objects, when there is little or no air resistance?
0
votes
0answers
16 views

Constructing uniform mesh in reciprocal space?

This is a bit of a mental exercise for me to get comfortable with the math of reciprocal spaces since I am going to start doing some research that requires knowledge of reciprocal spaces. Let's say I ...
0
votes
0answers
23 views

RC Circuit Analysis

I want to correct three misunderstandings about the following RC circuit. 1) How does current move directly after switch S gets closed? Current runs through all three circuit components to begin ...
0
votes
0answers
25 views

Fermionic oscillator and Hurwitz zeta function

Good resources for calculating Partition function of the fermionic oscillator using the Hurwitz zeta function? I liked the way Nakahara explain this, but some parts are really tricky for me (e.g. the ...
1
vote
1answer
101 views

Questions about the formalism of Quantum Mechanics

I have to do a presentation on this. I'm not expected to do something really detailed, but I'm not understanding the mathematical formalism. I would like to receive general answers to these questions: ...
-4
votes
0answers
91 views

Did NASA mistakenly create a warp field? [on hold]

There is this new article that claims that NASA could have accidentally created a warp field. How likely is that to be true ?
0
votes
1answer
48 views

How do the electrons know the route?

I've learnt in classroom that the requirements for electrical current to flow in a circuit are as follows: there must be a closed conducting path between negative and positive terminals there must ...
0
votes
1answer
17 views

Thermo - Plotting constant pressure and temperature on a Pv and Ts diagram

I was just curious what the saturation curve for water (plotting pressure versus specific volume) would look like if you drew both a line of constant pressure as well as constant temperature. I am ...
-1
votes
0answers
28 views

Formulas that cancel out time [on hold]

it's to my understanding that there are two simple physics equations that when combined and simplified that the terms for time cancel out. Could someone tell me what these formulae are (name and ...
10
votes
2answers
2k views

Why can't I do this to get infinite energy?

I know that I cannot do this because of conservation of energy, so I am looking for an answer as to why this will not work. So by my understanding of Einstein's whole famous $E=mc^2$ thing, it is ...
-2
votes
0answers
16 views

Find magnitude of the net magnetic field at points A, B, and C between two parallel wires [on hold]

I've been having a lot of problems with this problem. Been working on it for over to an hour and nothing. I've been using amphere's law but I think I'm getting r wrong, here's one of my most recent ...
0
votes
0answers
29 views

Calculating the 3-dimensional torque on a non-uniform rigidbody given the angular acceleration about its center of mass

Say I have a rigidbody, made up of several point particles with known masses and positions relative to the center of mass. How would I find the torque on this rigidbody given its angular acceleration ...
2
votes
0answers
64 views

Quantum Mechanics and Economics… What

I was reading this paper: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2002698&download=yes The author has the model presented here: ...
1
vote
2answers
76 views

What state does the particle in a box occupy?

My textbook derives the equations for the different energy states $E_n$ of the particle in a box. But my professor in class said this example was a good one because it spoke about the "superposition ...
3
votes
1answer
60 views

Where would the dark matter particle fit inside a picture of the standard model?

While I am particularly fond of the Sterile Neutrino, I have not been able to find any example of a picture of the standard model arrangement of particles, with Dark Matter (and the higgs), inside a ...
0
votes
1answer
41 views

General Relativity - Four Velocity Derivative Question

I am trying to get my head around a small point used in a book I am reading about General Relativity. The book states that because $u_au^a = c^2$ it follows that $u_a \nabla_b u^a = 0 $ The first ...
0
votes
0answers
22 views

Help with inclined slope motion? [on hold]

I have this question (5ii) and I was wondering why this wouldn't work, why can't I solve for acceleration using $v^{2}-u^{2}/2s$=$a$ then solve for $t$? I obviously have to resolve and use $p=fv$ but ...
-2
votes
0answers
27 views

Is Twin Paradox solved in Special Relativity or General Relativity? [duplicate]

I'm getting pretty frustrated about finding the true solution to the Twin Paradox. If I open 10 relativity books, they all tell that they have the correct solution and the other books are wrong. So I ...
4
votes
1answer
22 views

Does the Advanced Photon Source use electrons or positrons?

Synchrotron light sources like the Advanced Photon Source (APS) (as well as SPring-8 and the ESRF) are typically mentioned as accelerating electrons up to the GeV range to produce extremely high ...
0
votes
1answer
31 views

How to derive path difference ($\Delta l=d\sin \theta$) for double-slit interference?

The Wikipedia page for the double-slit wave interference experiment states that the path difference between waves diffracting from the two slits is equal to: $$ \Delta l=d\sin \theta $$ where $d$ is ...
1
vote
3answers
133 views

What is the meaning of “ Ψ is not a measurable quantity in itself”?

I want to know that why the wavefunction Ψ as a complex quantity (i.e $A+iB$ form) in quantum mechanics and somewhere I have studied that Ψ is not a measurable quantity in itself that's why we ...
0
votes
1answer
42 views

How to determine which object in a special relativity physics problem has proper time?

I'm having some difficulty determining which object/location should have proper time applied to it in relativity physics problems. Example: If an electron travels at 40% the speed of light then ...
1
vote
1answer
35 views

Can a brane have infinite volume?

I'm asking this within the framework of brane theory. My intuition is that branes are objects with finite volume, but then how can they accomodate an Universe that is infinite in extent?
1
vote
2answers
38 views

Electric field due to a finite line charge [on hold]

I was wondering what would happen if we were to calculate electric field due to a finite line charge. Most books have this for an infinite line charge. In the given figure if I remove the portion of ...
2
votes
1answer
24 views

Polarization of light for a fast moving observer

For a fast moving observer the frequency of light becomes shifted due to the (relativistic) Doppler effect. But what about the polarization of the light? Could it be, that e.g. circular polarized ...
1
vote
1answer
77 views

When will the pringles can fall?

When I'm pushing a tall, cylindrical object stood on its end (like a Pringles can) I can push it near its bottom, and it will slide forwards, or push it near the top, and it will topple over. So, ...
3
votes
1answer
38 views

Why is energy in a system typically able to be described using quadratic expressions?

This might be more of an applied math question. Why is the energy of a system typically able to be described using quadratic expressions. Is there an underlying mechanic that drives this?
2
votes
0answers
25 views

Current carrying conductor with a loop at a distance [on hold]

In Fig, there are an infinitely long conductive wire and a circle conductive loop C with the radius r and the number of turns n. The distance L between the wire and the loop is much larger than r, ...
10
votes
6answers
2k views

Can you ever exert more downwards force than your weight?

So, because I'm a hardcore person, I risked all this afternoon by going out in the wind, the rain and the cold to construct a willow den. Yes, it seems a menial task, but it was actually quite ...
0
votes
0answers
25 views

Does the Meissner effect only effect magnetic fields?

I find this effect very interesting and was wondering what tests have been performed to check its effects on other fields? Also a side question related to this effect, can it trap a magnetic field. ...
0
votes
2answers
17 views

For a light of given frequency, what does the amount of refraction in a variable medium depends upon?

I want to know whether the amount of refraction of a given monochromatic light depends solely upon the density of the of the medium ( increase the density to increase the angle of refraction), or ...

15 30 50 per page