# All Questions

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 ...
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 ...
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?
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.
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 ...
30 views

### Solve for emf in the circuit [on hold]

The ammeter is the circuit reads 2.0 A. What is the unknown emf?
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.
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, ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
25 views

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. ...
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 ...
584 views

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 ...
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 ...
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 ...
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 ...
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 ...
43 views

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'?