0
votes
0answers
4 views

Where is the net electric field 0?

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.
1
vote
0answers
5 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, ...
0
votes
0answers
6 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 ...
0
votes
0answers
5 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 ...
1
vote
0answers
10 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
12 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 ...
-2
votes
1answer
22 views

Based on newtons third law

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
10 views

Stokes-Einstein Relationship to find time taken to diffuse $x$ distance?

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
16 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
6 views

2-D Ising model temperature of equilibrium

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). ...
-1
votes
0answers
14 views

To find the eigen energy from the relation magnetic field [on hold]

How to find the eigen-energy from this picture. I get $E_i=(n+1/2)\hbar\omega$, but I'm not sure I am using the correct way
0
votes
0answers
5 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 ...
-1
votes
0answers
11 views

Force Of Attraction between 2 rings

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
1answer
22 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?
0
votes
0answers
12 views

Purity of reduced density matrix relation to concurrence

Given the quantum state: $$ |\psi\rangle=\alpha|0\rangle+\beta|1\rangle $$ If I perform the operation: I am pretty sure that the state after the CNOT operation: ...
1
vote
0answers
19 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
11 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
5answers
149 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 = ...
-1
votes
0answers
10 views

Determining Flight time Including Burst Time and Landing Time [on hold]

I really need your help, I am having a hard time to determine overall possible flight time on my High Altitude Balloon. I am part of a project and if you want I'll give credentials for the help. And ...
1
vote
1answer
18 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 ...
0
votes
0answers
11 views

Constructing a POVM to “almost distinguish” $m$ 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
26 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
8 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?
-2
votes
0answers
22 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
30 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
19 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
17 views

How to calculate impulse required to move an object vertically upward by given distance

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
19 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
15 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
23 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
20 views

Entropy for $N$ number of particles

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
1answer
22 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
20 views

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

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
19 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
21 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
14 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 ...
0
votes
0answers
40 views

Path integral (sum over paths where $v>c$)

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
8 views

Is it possible for dark energy density be decreasing?

I have an equation relating dark energy density and temperature, actually they have a linear relationship, according to that, the dark energy density must be decreasing with the temperature of ...
0
votes
2answers
37 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
17 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.
0
votes
0answers
10 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
12 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
23 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)
0
votes
0answers
12 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> + ...
-2
votes
0answers
16 views

How does a levy walker work?

I have read that a levy walker is a random walker which changes it direction after times which have power law distribution. is there any range for exponent of this distribution?
-2
votes
0answers
17 views

Wave drag explanation

I was reading a book and came across a definition, wave drag is the resistance from the waves created on the water surface by a moving object. I can't get it. Can somebody explain it with a diagram. ...
0
votes
1answer
25 views

What is the exact mathematical definition of oscillation/vibration?

My question is basically is what criteria need to be fulfilled to decide wether a motion is osciliiation/vibration or not. I found two definitions, def1: "moving around an equilibrum", def2: ...
0
votes
0answers
28 views

Why does thicker aluminum do better at reflecting wifi

I have performed a experiment based one the ability of aluminium reflecting wifi radio waves. I have found out that the more aluminium foil i put on my reflector, the better result I can get. I did up ...
-2
votes
0answers
26 views

Grand Unified Theory (Forces) [on hold]

Currently there two classes of forces Electromagnetic and Gravitational. Physicist are trying to unify the two. But is it possible? Electromagnetic force has a lot higher magnitude than ...

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