0
votes
0answers
5 views

Internal Energy of an ideal fermi Gas

The internal energy of an ideal fermi gas at temperature 0K is given by $$U=\frac{3}{5}NE_f$$ What conclusion can we draw from this statement.
0
votes
0answers
9 views

Conceptual question on Gauss's Law

By my understanding, the electric field in the surface integral expression for Gauss's Law represents the total electric field and any point on a closed Gaussian surface. However, when we employ ...
1
vote
1answer
27 views

Is it possible to see atoms ? There's a wikipedia picture

As per my knowledge atoms are smaller beyond our imaginations But there is a wikipedia image which shows silicon atoms observed at the surface of silicon carbide crystals. Here's the link to the ...
1
vote
0answers
9 views

Does a vacuum, suddenly opened, become hotter than its surroundings?

Suppose you have an insulated container that is equipped with a valve to let air in. Initially the container is evacuated. You then quickly open the valve, allowing air to rush in. What is the ...
1
vote
2answers
24 views

Why don't electrons fall on the ground, off the charged wire?

Please, don't mind if my question is silly, but I was always wondering... Imagine we have a negatively charged metailc wire. Let's assume it's just hanging on a thin rope. What force keeps electrons ...
0
votes
1answer
11 views

Application of BEC in Helium-4

By using the formula for Transition Temperature, we can obtain the Transition temperature for Bose Einstein Condensation to occur at 3.14 K, however, it shows the properties of superfluidity at 2.18 ...
0
votes
1answer
13 views

Chemical Potential as a function of Temperature

I have considered an ideal fermi gas. Then, we can obtain an expression for chemical potential as a function of Temperature. I want to understand the physical significance to it or what it really ...
1
vote
1answer
14 views

Getting the velocity of self-diffusion from the einstein relation

I have been reading about self-diffusion of a particle here: http://www-hsc.usc.edu/~rfarley/Diffusion-SI-2003.pdf and on page 9 it gives Einstein's relation as $(\Delta x)^2 = 2 D t$ and I can ...
1
vote
1answer
24 views

Do we need Escape Velocity

This may seem silly a lot but I really need some clarification on the necessity of escape velocity for a rocket leaving the Earth's gravity. A stone thrown vertically upwards reaches to a certain ...
-1
votes
0answers
14 views

How to explain the constancy of physical structure

My question will may be seems awkward, naïve and my learning level in physics is not very high. But I was wondering how physical structures from the atom to macroscopic ones, including living beings ...
0
votes
0answers
9 views

Equations of Motion Lab Experiment [on hold]

I did a lab experiment in physics class but I'm having difficulty approaching these questions. I'm thinking that the graph that I'd sketch is a position- time graph which would be the answer for ...
0
votes
3answers
17 views

Why capacitor pass AC and block DC current? [duplicate]

We know that in circuit capacitor block the DC current and pass AC current. My question is how a capacitor block DC and pass AC?
3
votes
2answers
140 views

Where do photons go when they are absorbed?

The answer I usually get (and I'm paraphrasing here) is that they disappear and are instead absorbed as heat energy. But I find it hard to believe that the photon simply "disappears." Common sense ...
0
votes
0answers
7 views

Bloch Hamiltonian of low energy edge mode of a 2D topological insulator

First time to pose a question here. It's a Hamiltonian appears in this paper https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.87.137 The equation (71) $$ h_0(q) = v q\sigma^y+m\sigma^x-\mu ...
1
vote
0answers
12 views

Intuition for Homological Mirror Symmetry

first of all, I need to confess my ignorance with respect to any physics since I'm a mathematician. I'm interested in the physical intuition of the Langlands program, therefore I need to understand ...
0
votes
1answer
11 views

Does displacement current occur in an inductor?

We have learned in school that displacement current comes about due to a change in electric field flux per time in a capacitor (Ampere-Maxwell Law). Does the same displacement current come about in an ...
-1
votes
0answers
12 views

A moving object appears to move faster towards you and slower away

First: So sorry if I'm posting this in the wrong section Also, no, this is not a question. It is a theory of mine. But, relating to the previous line, I don't know where else I would put it. Okay. ...
0
votes
0answers
11 views

Hamiltonian for semiconductor

I was wondering which terms we need in a semiconductor Hamiltonian where no transition between the valence and conduction band occur? First we would have a term describing the energy of the full ...
2
votes
2answers
89 views

The relationship between light and magnetic fields

I have two questions. Does light have a magnetic field? If not, can it be affected by other magnetic fields?
0
votes
3answers
28 views

Where is the energy stored in destructively-interfering waves?

Let's say we have two waves moving along a string. One of them is represented by the function: $$f_1(t)=\sin(\omega t)$$ The other one is represented by a function: $$f_2(t)=-\sin(\omega (\tau-t))$$ ...
1
vote
0answers
24 views

General solution of the four-vector with each component satisfying the wave-equation

Maybe this is more appropriate for Math stackexchange, but this question regards the solution we use in order to find representation for massive / massless spin-1 particle. When $$(\Box + m^2)A_\mu = ...
2
votes
0answers
39 views

How to find creation and annihilation operators?

I get confused when trying to find this. Please describe it as simply as possible, but keep in mind I have no budget whatsoever to pay for textbooks, so here goes: How do you find the creation and ...
0
votes
0answers
19 views

Has the cosmic alignment of Earth and the Solar System been explained (CMB anisotropy)

The Cosmic Microwave Background anisotropy is currently aligning Earth and the Solar System with the largest and earliest structure of the universe. Has this been explained yet? Or are the theories ...
0
votes
0answers
28 views

Does Big Bang Cosmology imply/require infinite space?

The reason I am asking this question is because if all points in space observe recession of galaxies the same as we do from Earth, the universe would have to be infinite (or a closed sphere in 4D or ...
0
votes
3answers
39 views

Intuition behind Rocket propulsion equation [on hold]

What's the intuition behind the Tsiolkovsky rocket equation: $$v - v_0 = v_{ex} \ln{\frac{m_o}{m}}.$$
3
votes
0answers
16 views

Phase Transition at Zero Temperature (Not QPT)

As is well known the Ising model exhibits a phase transition, except the one dimensional case in which the phase transition occurs strictly at $T=0$. Now I have always thought that this makes the case ...
4
votes
1answer
57 views

Solution of the wave equation

The solution of the wave equation \begin{equation} \frac{d^2y(x)}{dx^2}+k^2 \left(1+\eta(x)\right) y(x)=0 \end{equation} Can be found by using the Green function method as \begin{equation} y(x)=c_1 ...
1
vote
0answers
28 views

Spectral lines and QM

In the various presentations I've seen so far in atomic physics of series such as the Balmer series, the wavelength of each spectral line is definite - but in QM, free particles have no definite ...
1
vote
1answer
26 views

Potential Energy, Kinetic Energy, velocity, question?

A man standing a certain height above the ground throws a rock straight up with an initial velocity of $10 \:\mathrm{m/s}$. A few moments later, the rock hits the ground with a kinetic energy of ...
1
vote
2answers
37 views

What is the minimum velocity a toy car has to travel in order to survive going through a loop of radius 0.2 meters?

I tried height = 2 * radius = 2 * .2 m = .4 m. Potential energy = mgh. Kinetic Energy = $\frac{1}{2}mv^2 = mgh$ Then $\frac{1}{2}v^2 = gh$ $v = \sqrt(2gh) = 2.8 m/s$ The correct answer is 2 ...
5
votes
1answer
31 views

Why is a hexagon such a stable shape for materials?

A hexagonal lattice is famously the shape of graphene, the source of the 2010 Nobel prize. The shape also shows up in beehives and in the basalt columns of Giant's Causeway in County Antrim. ...
-1
votes
0answers
28 views

Ratio of kinetic energy concerted to internal energy [on hold]

I need help with this question: Consider four identical cars. Two of them collide head-on when both are traveling at 34 m/s. The other two collide head on when both are traveling at 25 m/s. What ...
-7
votes
0answers
20 views

Help! I need to know the category and subcategorie hlp [on hold]

i would like to know the dimensions of aXb in the relation p= b-x^2/at where p is power, x is distance and t is time
2
votes
1answer
40 views

Estimating divergence of set of vectors

I have a set of points where directions and intensities of a flow are given (in 3D). Is it possible to estimate the divergence of the flow defined by those vectors? I only need a rough estimate and I ...
1
vote
0answers
22 views

Microscopy: aperture matching and Huygen's principle

I have repeatedly read that the maximum spatial resolution of a microscope occurs when the aperture of the objective and condenser are the same. However, I don't understand why. The resolution is ...
1
vote
0answers
10 views

Have there been any experiments that have demonstrated a quantum error correcting code?

Has quantum error correction been demonstrated? I know that classical error correction has been demonstrated by [1], they correct a single bit flip error, but has anyone been able to detect and ...
3
votes
6answers
255 views

Can we change a photon's frequency in mid-air?

Can we have a light source emitting photons in the infrared range and after, lets say, 5 meters, these photons become a photon in the x-ray range? The only way I know we can change a photon's ...
1
vote
2answers
48 views

Is my answer possible? (Newtonian Third Law Pairs and Forces, Multiple Choice Word Problem)

So I recently took a test and the teacher graded my answer correct, yet my friends saw that the other answer was correct and they protest that it should be the right answer: The question goes: ...
1
vote
1answer
57 views

How can I use Einstein's field equations?

Every time I try to find the answer to this question I get redirected to different pages that ultimately do not end up answering my question. I have some understanding of Riemannian geometry but have ...
2
votes
1answer
20 views

Conductor held at constant potential

What does it mean for a conductor to be held at constant electric potential? So if my reference point is infinity, and I integrate inwards over the electric field to any point on the conductor, I will ...
0
votes
1answer
34 views

If a charge needs potential difference to move

Let's consider a circuit with a ideal source of emf and a resistor. Consider the segment of wire that connects emf with resistor. If we measure potential difference at any point of the wire, this will ...
2
votes
2answers
33 views

Directly calculate electric potential due to a spherical volume charge

Q: Say we have a uniformly charged sphere with radius $R$, total charge $Q$. Now we need to find out the electric potential inside the sphere, at a distance r from the centre. I understand that we ...
-3
votes
3answers
32 views

Given Force in vector form, how do I find work done? [on hold]

A force of $F=\hat i+2\hat j-3\hat k$ is applied to a particle that moves 10 meters in the direction of $\hat i+\hat j$. How much work is done?
1
vote
4answers
345 views

What is the universal speed limit relative to? [duplicate]

If all speeds are relative, then what "governing" force is that speed limit relative to? Is there some sort of fixed or absolute grid with locations everything is compared to? Does this also mean ...
0
votes
0answers
19 views

Voltage induced in coil

Okay, so I have two coils. A ring of radius $R$ is stationary at origin. A coil of $N$ turns and area $A$ carries current $I$ and is moving along the $x$ axis such that $x = x_0 + cos(\omega t)$. ...
-2
votes
1answer
50 views

Are there nonlinear models of quantum mechanics which forbid superluminal signaling?

What would a nonlinear model of quantum mechanics which forbids superluminal signaling look like? Of course, a nonlinear $\psi$-ontic theory with entangled states could have superluminal effects upon ...
-5
votes
0answers
20 views

equilibrium pulley system [duplicate]

the question asks what mass i need for m1 to be in static equilibrium while m2 is given as 60kg. im not sure first of all if that means the two masses have to be equal in length balanced. secondly, ...
1
vote
1answer
51 views

How do I find the angle given the mass, the acceleration and the force acted on a body?

My Issue I have the mass, the horizontal acceleration and a force that acts on a body. The force forms an angle $\alpha$ of unknown degrees with the x-axis. I would like to know how I can find the ...
-1
votes
0answers
33 views

Calculating Hall Effect in Semiconductors Without the Hole Convention

** Edited to be a clearer separate question from some existing ones ** We should be able to do solid state physics without recourse to the hole convention (although less convenient: Holes in a P-type ...
-2
votes
0answers
55 views

mass needed for equilibrium in pulley system [on hold]

Question says: For what m1 will the illustrated pulley system be in static equilibrium if m2 = 60 kg? ive tried equating the changes in length where change in x1 is equal to twice the change in x2 in ...

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