-3
votes
0answers
31 views

Dark energy and magnetic field [on hold]

I have learned that a photon creates it's own magnetic field. Arno Penzias & Robert Wilson discovered the background radiation from the Big Bang. Could this also be the time of the creation of ...
2
votes
1answer
58 views

What do the batteries actually do to the electrons?

I am plagued by this simple question that what force exactly causes the motion of an electron in the middle of a lattice of electrons of a wire? a. Is it an electric field created inside a wire due to ...
0
votes
0answers
26 views

Rotation operation on spin-1/2 particles

How does rotation operators work on a particle? What does it do on the particle conceptually? Also does particles spin on its axis?
4
votes
3answers
57 views

Unified Theories

How can a unified theories help us? Like after unifying electromagnetic and gravitational forces will there be some ease on how we study forces? PS: This is my first SE post.
1
vote
3answers
371 views

What will happen to a man if he hangs from the power cable of train using one hand and secondly using two hands? [duplicate]

If a man holds and hangs from the power cable of trains with one hand, will he be alive or will he die if he holds and hangs from the electric wire using two hands without touching the ground ? I ...
-3
votes
0answers
30 views

Solve for emf in the circuit [on hold]

The ammeter is the circuit reads 2.0 A. What is the unknown emf?
-4
votes
0answers
26 views

Where is the net electric field 0? [on hold]

A positive charge +3Q is separated by a distance, d, from a negative charge -Q. What is the closest distance in which the net electric field is zero.
3
votes
2answers
31 views

Creasing of a material at the molecular level

What exactly happens when a material (particularly paper or even cloth or a metal) is folded to form a crease? Why is it that a creased material tends to retain form, while a lightly folded one, ...
3
votes
0answers
54 views

S-matrix and derivative interaction

I just read in some lecture notes that formally we can write the S Matrix as: $$S=T(e^{-\int_{-\infty}^{+\infty} H_{int}dt}) $$ Where $T$ is the normal product and $H_{int}$ is in the interaction ...
1
vote
0answers
15 views

what is the effect of temperature on the resistance of a photoconductor?

As we know, for a photo conductor resistance tends to decrease with increase in irradiance, but with greater irradiance comes greater temperature. Also we know, photo conductors are ...
2
votes
2answers
52 views

Why do some people support more electricity than others?

There is a game where people hold by their hands and two of them touch the electrodes of a shock box, then an electric current flows through them. I understand that since they are all making a single ...
-1
votes
1answer
22 views

Question on weightlessness

An astronaut in an artificial satellite of the earth feels weightlessness. Do they feel weightlessness on the moon too? Why? An astronaut in all artificial satellite feels weightlessness due to the ...
-3
votes
1answer
47 views

Based on newtons third law [on hold]

If an elephant can apply 250N force and a rabbit can apply 25N force , and if they are pulling each other , then elephant will pull with 250N force and according to newtons third law the rabbit should ...
-1
votes
1answer
17 views

Stokes-Einstein Relationship to find time taken to diffuse $x$ distance? [on hold]

A molecule has a diffusion coefficient of 0.5 × 10-9 m2s-1. Calculate how long it would take on average for the molecule to diffuse 10 µm. So I have the above ...
1
vote
0answers
25 views

Meaning of Hamiltonian between two different states

If we have states $\left | 1 \right>$ and $\left | 2 \right>$, and the Hamiltonian operator $\hat{H}$, what is the meaning of the expression $$\left< 1 \right | \hat{H} \left | 2 \right ...
0
votes
0answers
17 views

2-D Ising model temperature of equilibrium [duplicate]

I have simulated 2-D Ising model in C#, but my scatter plot for magnetization versus temperature is an decreasing line (you know that the correct plot decreases quickly in a temperature near 2.3). ...
2
votes
1answer
24 views

How does negative power lead to amplification?

I am currently investigating semiconductor superlattices and I am analyzing the negative differential velocity (NDV) after a certain limit. I understand how NDV leads to negative power, but I am ...
0
votes
0answers
22 views

Force Of Attraction between 2 rings [on hold]

We have 2 rings of say equal radii (for simplicity) separated by a distance d. I ring carries +q charge and the other -q. I wish to compute the electrostatic force of attraction between these. Is it ...
0
votes
2answers
39 views

Thermal Capacity

An electrical heating coil of power $P$ is used to transfer thermal energy to a body of mass $m$. In a time $t$ the body changes temperature by $\Delta T$ . What is the thermal capacity of the body?
-1
votes
0answers
47 views

Relating purity of reduced density matrix to concurrence [on hold]

Given the initial quantum state: $$ |\psi\rangle=\alpha|0\rangle+\beta|1\rangle $$ If I perform the CNOT operation: I get the two cubit state: $$|\Psi'\rangle=\alpha|00\rangle+\beta|11\rangle \ ...
1
vote
0answers
22 views

Bremsstrahlung in body tissue

As far as I know, the intensity of the produced radiation from bremsstrahlung is proportional to: $$I \propto \frac{Z^2}{m^2},$$ where $Z$ is the atomic number, and $m$ is the mass of the particle. ...
0
votes
0answers
16 views

Construct recurrence relation for the temporal evolution of a Master equation

Say that we have a system evolving over discrete timesteps. The quantity we are interested is X and is given by a distribution $P_X$. This distribution is evolving temporally, and we have a ...
8
votes
4answers
584 views

Which formula for the de Broglie wavelength of an electron is correct?

So, I have my exams in physics in a week, and upon reviewing I was confused by the explanation of de Broglie wavelength of electrons in my book. Firstly, they stated that the equation was: $\lambda = ...
-3
votes
0answers
31 views

Is there anything wrong in this document? [on hold]

https://www.mediafire.com/?m39l0t6bwd29241 Although the last line is not finish thou, I am confused about the Gas laws and how it may affect the volume of the gas inside the balloon
2
votes
1answer
26 views

Bent capillary tube

What would happen if I bend a capillary tube and use it as shown in figure? 1.Will the water(or any other adhesive liquid) level remain same as before bending? 2.or it will come up till end? 3.Or ...
2
votes
1answer
36 views

Constructing a POVM to discriminate $m$ quantum states. What if they're linearly dependent?

I've come across this problem in Nielsen & Chuang's Quantum Information book (problem 2.64) Suppose Bob is given a quantum state chosen from a set $|ψ_1 \rangle, . . . , |ψ_m\rangle$ of linearly ...
1
vote
1answer
34 views

Does density of air decrease or increase with altitude and relation of this with temperature?

I think the air density decrease as due to gravity more air woul be near the earth but as the hot air raises up doesn't it have momentarily increased the density at height (like in up troposphere) ...
1
vote
0answers
11 views

Net force of a falling down people by Resolution of Force. [on hold]

From the picture, I want to calculate the Force (F) when people fall down. I searched the internet, but I have no findings. Given that Mass (M) = 75 kg, Gravitational force (G) = 9.81 N. How can I ...
-1
votes
0answers
9 views

Explain quality factor and bandwidth [duplicate]

Can anyone explain concept of quality factor and bandwidth with a mechanical example?
-3
votes
0answers
25 views

Einstein and his idea about infinite electricity [on hold]

What did Einstein say about infinite electricity? Did he say that,it is impossible?
1
vote
1answer
48 views

Cosmic Rest Frame

Cosmic Rest Frame is defined in the paper "Adventures in Friedmann cosmology :A detailed expansion of cosmological Friedmann equations" by R Nemiroff and B Patla as the frame at a point where average ...
-1
votes
0answers
21 views

What is the answer to the numerical given below? [on hold]

An electron revolves along a circular path of radius 20cm with constant angular velocity 120 rad/s about an axis passing through the centre and perpendicular to the plane of the circle. if the ...
0
votes
1answer
21 views

How to calculate impulse required to move an object vertically upward by given distance [on hold]

Suppose I have a stationary object of mass $m$ and I want to apply a momentary force in the vertical direction so that it just reaches the height $h$. So how do I calculate the impulse required in ...
0
votes
0answers
26 views

Lorentz sphere correction

I am studying Lorentz surface correction for magnetic fields. I know that if we consider a uniform distribution of magnetization, the field can be computed as three contribution: $H+H'+H''$ where $H$ ...
0
votes
1answer
16 views

Force applied between neighboring atoms resulting in increase in separation

I am attempting a past paper question in practice for an upcoming exam and I am a little lost with the following question: Using lennard Jones model for potential. An external force $F$ is applied to ...
0
votes
1answer
29 views

2nd law of thermodynamics - simple steam power plant problem

A steam power plant consists of a boiler, a turbine, a condenser and a pump. The temperature of the inner walls of the boiler is 350 °C and the temperature of the condenser cooling water is 20 °C. ...
-3
votes
1answer
33 views

Entropy for $N$ number of particles [on hold]

If there are $N$ number of non-interacting and distinguishable particles which have either Energy $E_1$ or $E_2$ , then a. What will be the entropy $S(n)$ for such system? ($n$ is the number ...
1
vote
2answers
55 views

Why does internal resistance increase as current decreases?

Our class conducted and experiment to investigate internal resistance and terminal pd, using a cell, fixed resistor and variable resistor. The results were as follows: As the resistance of the ...
0
votes
0answers
28 views

How to calculate the vector potential $A$ inside an infinite cylinder using Poisson's equation? [on hold]

Poisson's equation is : $$ \Delta \boldsymbol A = - \mu_0 \boldsymbol J$$ we want to calculate $\boldsymbol A$ inside an infinite cylinder with radius $a$ and the current density is $\boldsymbol ...
0
votes
1answer
23 views

Moment of inertia and gravity

Would the objects have moment of Inertia if there was no gravity? Because imagine a bar, if I put my hand at the center of the bar and rotate it, it would be easier than rotate the bar picking one ...
2
votes
3answers
29 views

Why does a pot start rotating when coffee is stirred inside?

I usually make Turkish coffee as my morning coffee. I have a small somewhat rounded pot with handle on one side. I noticed that when I pour water in and start stirring, pot has a tendency to start ...
0
votes
0answers
19 views

Why is more difficult for a DFT to converge with non-periodic conditions?

I am simulating a cubic amorphous silica system. When all boundaries are periodic the SCF iteration converges rapidly. However, when the boundary is not periodic in the $x$ direction, the SCF ...
1
vote
0answers
54 views

Path integral (sum over paths where $v>c$) [on hold]

The path integral formalism is used to get for example the propagator of particles. In this formalism we integrate over all mathematically possible paths (and weight them with the non-relativistic ...
1
vote
0answers
25 views

Is it possible for dark energy density be decreasing? [on hold]

I have an equation relating dark energy density and temperature, actually they have a linear relationship, my question is how to choose the temperature? If I choose the temperature of universe, the ...
0
votes
2answers
43 views

Increase in entropy principle

If we consider a system to undergo an irreversible process from state 1 to state 2 and a reversible process from state 2 to state 1, then through Clausius inequality $\int_{1}^{2} \frac{\delta ...
-1
votes
0answers
24 views

Dimensional Analysis Problem [on hold]

In the formula: $$ P = nRT/(V-b)* e^{-a/(RTV)}\ $$ Find the dimensions of 'a' and 'b', where P = Pressure , n = No. of moles , T= Temperature , V = Volume and R = Universal gas constant.
1
vote
0answers
18 views

Extensiveness of entropy in classical microcanonical ensemble

In introducing microcanonical ensemble of classical statistical mechanics one pretty much starts by postulating that entropy of the system has the form $S(V,E) = k \log \Gamma(V,E)$, where $\Gamma$ ...
-1
votes
0answers
13 views

What is the relation between rhymes in terms of their wavelengths?

How are the wavelengths of any 2 rhyming words related? Eg: How is the wavelength of the sound produced bye 'fee' related to the sound produced by 'see'?
0
votes
2answers
27 views

Phase difference in currents in parallel RC circuit

shouldn't the phase difference be 0. The potential difference across any branch at any instant should be V.so what's wrong ?btw correct answer is (C)
-1
votes
0answers
15 views

Is this state an example of a separable state or an example of an entangled state?

The Hong–Ou–Mandel effect also underlies the basic entangling mechanism in linear optical quantum computing (https://en.wikipedia.org/wiki/Quantum_computing), and the two-photon quantum state |0,2> + ...

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