# All Questions

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### Colour of ocean water

Why does ocean water seem blue colour in some regions while green in some regions while river of pond water is never blue in colour?
106 views

### Is Hamiltonian a differential operator in second quantization?

Normally, a free particle Hamiltonian is written $$\hat{H} = - \frac{\hbar^2}{2m} \Delta$$ which is a differential operator because Laplacian $\Delta$ is. On the other hand, in second ...
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### Rotate a small wheel using magnets

I know this question already asked so much times. I tried to rotate a wheel by placing few magnets on it. And I used some powerful magnet and repel it using opposite poles in the magnets placed in a ...
38 views

### Electric field between capacitors [on hold]

A parallel-plate capacitor consists of two parallel, conducting plates of area $A$, separated by a distance $d$. Each carries a charge of magnitude $Q$; positive on one, negative on the other. ...
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### Why do physicists believe that there exist magnetic monopoles?

One thing I've heard stated many times is that "most" or "many" physicists believe that, despite the fact that they have not been observed, there are such things as magnetic monopoles. However, I've ...
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### Is it accurate that light loses energy in the absence of gravity and gains energy in its presence?

I just read an article about the supervoid they found and this is suggested. If so, then I am more and more fascinated with the ties between light and gravity. Let me emphasize, every article that I ...
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### Do matter and antimatter annihilate or release energy?

Do matter and antimatter eliminate each other or release their equivalent energies? I'm almost certain it's the latter as mass can't be destroyed, but when speaking of the big bang it's said if there ...
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### Do atoms behave like waves? [duplicate]

I've heard someone state that the double slit experiment can also be done with atoms, not just electrons or photons of light.
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### Calculating deceleration time - help! [on hold]

I'm struggling with a question due to not having the correct formula, so I hope someone can help! A 10000kg object is travelling at 15m/s, and a force of 600N is applied in the opposite direction to ...
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### Minimum set of theories to rule them all [duplicate]

What is the complete (and minimal) list of theories that wraps everything we know in physics? e.g.: Is General Relativity a superset of Newton's theories, or an addentum? Does quantum ...
117 views

### Entropy / Structure Relations

I want to check on the validity of the following objective definition of order. Is it correct? Is there a more rigorous statement of this concept? The further a system is from its maximum ...
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### Local minima in Ising model in a Monte Carlo simulation

Is there any way to check whether in a Monte Carlo simulation using Ising model is stuck in any (false) local minima of energy or not, particularly in 3D system ?
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### Is all of the energy dissipated in a magnetic core in the form of heat and can any of it be recovered?

In an AC motor where you use a laminated magnetic core to shield the induction process from eddy currents, the field lines that run through it result in core loss through heat. Is all of the energy ...
105 views

### Isn't a physical frame of reference useless for calculating speed?

Please ignore relativistic effects and the effects of the expansion of space-time due to the expanding universe theory for the purposes of this question. Whenever someone asks what is the speed of X, ...
156 views

### Induced electric field due to a moving wire

An infinite wire carrying a constant current $I$ in the $\hat{z}$ direction is moving in the $y$ direction at a constant speed $v$. Find the electric field, in the quasistatic approximation, at the ...
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### Why is this circuit component on without a potential difference?

From the following graph, determine whether (h) will be on or off: I think (h) should be off because there is no potential difference across it. Is this correct? Edit: Using the method provided ...
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### What is a wavelength of an EM wave physically?

This might be a silly question given I am a physics undergrad, but I was suddenly confused. Usually when EM hit a gap they diffract through the gap. But if the gap is too small, diffraction can't take ...
1k views

### Is it possible to generalize the Maxwell equations to higher dimensions?

The usual Maxwell equations are for 3 spatial dimensions, right? Is it possible to generalize them to 2 spatial dimensions or 4 spatial dimensions?
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### Internal Resistor in a Diode

When we talk about the resistance of a diode (of the P and N region), is this resistance like the one inside an Electro-Motive Force or it acts like a normal resistor (external electric field exist)? ...
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### How can I obtain a unit vector of a shifted spherical system? [migrated]

I hope that I can explain myself clear enough, Assuming i have a sphere that has been moved down in the Z-axis. I know that the radial unit vector when the sphere is not shifted can be expressed as: ...
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### Does the effect of spaghettification mean that (speculative) traversable wormholes can only exist from supermassive black holes? [on hold]

Assumption that wormholes really exist. Even if humanity could produce wormholes from quantum black holes. These would be never traversable due to the effect of spaghettification? Or does the exotic ...
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### Maxwell in multiple dimensions: What happens to curl?

I read this answer a while ago, and while thinking about $\nabla$, I realized something. Since the cross product can be written as a determinant, in higher dimensions we require extra vector inputs. ...
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### thermodynamics question [on hold]

I've thought this question for a really long time and now i need help..... The question is "the volume occupied by a mole of liquid water at 100 degrees celcius is (1.87 exponent -5) cubic metres. ...
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### The velocity of the image if both the mirror and the object start moving [on hold]

Suppose a vertical plane mirror and a object which is placed at a distance of 4 m from the mirror. If we start moving the mirror with a velocity of 2m/s and also start moving the object at 3m/s. Then ...
Find the angular displacement $\theta_1(t)$ and $\theta_2(t)$ of the system shown in figure below for the initial conditions $\theta_1(0)$, $\theta_2(0)$, and $\dot{\theta}_1(0) = \dot{\theta}_2(0) ... 2answers 39 views ### Topological insulators literature I started learning things on topological insulators and I got lost in dozens of existing papers on this topic. Could anyone recommend me appropriate literature that explains deeply enough what ... 1answer 207 views ### Good source for numerical simulations of Wigner function? I'm interested in simulating the time evolution of a Wigner function for a harmonic oscillator (and possibly some other potentials) and I can't seem to find a good resource for that. My background in ... 1answer 205 views ### Proton scattering off electrons I'm looking at a question which starts off as: A proton is travelling through a material and scattering the electrons in the material. Express the scattering angle in terms of the impact parameter, ... 1answer 27 views ### Gravity's tall box with a ball inside - scenario Let's imagine we put a ball inside a box such that it doesn't touch its walls, and suddenly drop the box. Because the two objects fall at the same rate of acceleration, the ball will stay at the same ... 5answers 2k views ### Is the speed of light in vacuum always the same value? The escape velocity of different planets and stars vary. If they vary, the velocities of bodies escaping from the respective stars or planets should also vary. Like, if I want a ball to reach 10 ... 1answer 101 views ### Why are nonrelativistic methods used in binary pulsar systems (gravitational waves)? Although gravitational waves are a subject of the General Relativity, why do most books use Newtonian equations of motion for power radiated and rate of change of eccentricity calculations? In most ... 1answer 21 views ### how covalent bonding lower the energy of potential energy Considering the potential energy of interacting particles, how does covalent bonding lower the energy of the system? 1answer 203 views ### Series / parallel capacitor network: find two capacitances and source voltage given some measured data Capacitor 3 in Figure (a) is a variable capacitor; its capacitance$C_3$can be varied. Figure (b) gives the electric potential$V_1$across$C_1$versus$C_3$. The horizontal scale is set by$C_3 = ...
From page 35 of "Microelectronics" by Millman Grabel Mobility $\mu$ decreases with temperature because more carriers are present and these carriers are more energetic at higher temperatures. ...