12
votes
6answers
22k views

What are the fields produced around a current carrying conductor?

If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged ...
17
votes
2answers
195 views

Is there an official name for “Lorentz Pairs” like energy and momentum?

In learning about relativity I've noticed that in the construction of Lorentz invariants (specifically four-vectors) two physical quantities that were previously considered distinct are instead ...
4
votes
1answer
128 views

Physics engine - collisions

I'm working on a 2D physics engine somulator and I want it to be very accurate on a Physics point of view. Currently I'm making some researchs about how rigid body collisions may be calculated, and ...
5
votes
1answer
91 views

Stability theory [closed]

I'm studying stability theory recently and met a lot of phrases like linear stability and nonlinear instability. After searching on Google, I became more confused. Thus I wonder if there is any ...
2
votes
1answer
197 views

Meaning of Lagrange Multiplier in Ou-Yang and Helfrich's Shape equation for Membrane

Dear people in Physics Stackexchange, My question is mostly related to the following papers: U. Seifert, Z. Phys. B 97, 299 (1995). "The concept of effective tension for fluctuating vesicles". U. ...
14
votes
8answers
11k views

Can the magnetic lines of force of two or more magnets intersect each other?

Basic property of magnetic lines of force is that, they can never intersect each other. Among the two points given below, which one is correct? Magnetic lines of force of same magnet can't intersect ...
3
votes
1answer
442 views

Determining Fourier Coefficients by inspection

I'm beginning to learn about Fourier series/transforms. My teacher hopes that by now we should be able to examine a simple potential function and decompose it without having to actually do the ...
3
votes
2answers
1k views

Energy density in Magnetic fields?

I don't understand what does magnetic field energy density stand for? The possible work that the magnetic field can do? So we can calculate the amount of "work" it can do just from the energy density? ...
15
votes
5answers
2k views

Why isn't absolute $0 K$ temperature possible?

So $T$ is defined as $$T = \left(\frac{\partial E}{\partial S}\right)$$ and $S$ is defined as $$S = k_B \ln \Omega$$ where $\Omega$ is the number of accessible states of the system for a given ...
1
vote
1answer
2k views

Direction of tension?

If you draw the free body diagram of the frame above, what direction would the tension force acting on the frame be - to the right or down? Because the rope it horizontal at some points but vertical ...
2
votes
1answer
199 views

Problem Of Lazy Fish [closed]

Fish achieve neutral buoyancy (so they don't have to swim constantly to stay in place) via a swim bladder. A swim bladder is a little internal sack that they can inflate/deflate with air, which ...
4
votes
1answer
70 views

Problem Of Pumping Rubber [closed]

One can work out by either lifting weights or using a tension band, which is like a big rubber band. If we model the rubber band as a big spring with spring constant $400 N/M$ how far in meters must I ...
6
votes
5answers
1k views

Infinite Wells and Delta Functions

In considering a delta potential barrier in an infinite well, I can just enforce continuity at the potential barrier-it doesn't have to go to zero. Why then does it need to go to zero at the walls of ...
3
votes
1answer
409 views

Scale Factors via Ellipsoidal Coordinate System Scale Factors

In Morse & Feshbach (P512 - 514) they show how 10 different orthogonal coordinate systems (mentioned on this page) are derivable from the confocal ellipsoidal coordinate system $(\eta,\mu,\nu)$ by ...
3
votes
1answer
99 views

What is the correct form of the NHEK metric?

I've noticed that in different articles people are writing the near horizon extreme Kerr metric (NHEK) in different forms. Original Kerr/CFT correspondence article by Guica et. al. follows ...
1
vote
2answers
734 views

Quantum Mechanics Operator Hermiticity

If $A$ and $B$ are Hermitian operators, show that $$C~:=~i[A,B]$$ is Hermitian too. My work: $$\begin{gather} C=i(AB-BA) \\ \langle\psi\rvert C\lvert\phi\rangle = i\langle\psi\rvert ...
0
votes
3answers
3k views

Does rate of acceleration affect the amount of energy used to accelerate?

Assume you start with a car at rest. Then you accelerate the car to 100 kilometers per hour. In terms of the energy needed, does it matter how fast you accelerated the car? In other words, do you ...
5
votes
1answer
426 views

Question about Neutrino Flavor and Mass Eigenstates

I know the flavor and mass eigenstates are different, but are they related? What I mean is, in a process like fusion where electron neutrinos are created, do they start in the 1 mass eigenstate? My ...
4
votes
3answers
203 views

Will the current carrying solid conductors emit light?

If we pass current through a gas, like in the discharge tube, the electrons will accelerate in the electric field. The accelerated electrons will collide with gas molecules, and transfer some of their ...
0
votes
1answer
134 views

counting refractive index of a plano convex lens [closed]

suppose that, there is a plano convex lens and its thickness is 5.00cm. If you watch it straight from the convex side, it seems that its of 4.4 cm. What is the refractive index of this lens?
9
votes
6answers
2k views

Can a conductor run out of electrons to cancel external electric fields?

We have studied so far that electric field inside a conductor if no charge is placed inside is zero. But we know that every conductor has only a limited number of electrons. What happens when ALL the ...
3
votes
1answer
100 views

Can polarization effect the coherence length?

I'm taking an optics lab in which I'm required to construct an interferometer, and measure the wavelength of a laser, and the coherence length of the light emitted from a candle fire. Now, I've been ...
1
vote
0answers
53 views

Do two synchronous clocks have simultaneous indications?

Considering two clocks, $C$ and $D$, which were at rest to each other throughout a sufficiently extended trial, and given their time parametrizations $t_C : {\text{ ordered set of}}C{\text{'s ...
4
votes
3answers
1k views

Real image with converging lens?

I read in a AQA GCSE book that: A real image is formed by the converging lens if the object is further away from the principal focus/focal point. I did this experiment in class: Here is my ...
0
votes
1answer
507 views

Hamiltonian operator apply to a wavefunction

When a Hamiltonian operator apply to a wavefunction, how could we write the hamiltonian as, $$H \psi = (E_n-\hbar \omega_0) \psi \ \ ? $$ Is this because $E_n= H+ \hbar \omega_0$? where ...
1
vote
1answer
92 views

Basic vertical projectile motion

A ball is thrown from the top of a tower with a certain initial speed. It's downward acceleration is g. But why? the initial force makes no difference? and, if not, if I get a revolver and shoot down, ...
0
votes
1answer
660 views

Muon 3 Body Decay

I'm trying to calculate the maximum energy of the electron in the decay muon >electron + electronantineutrino +muonneutrino in the reference frame of the muon having no kinetic energy. $m_m$=mass of ...
-5
votes
1answer
255 views

traditional transformer design improvement [closed]

The traditional tranformers suffer a lot of losses in various forms, some of them are as follows : 1. Flux leakage 2. Eddy currents 3. Hysteresis Figure : But as we are taught induction we come ...
-4
votes
1answer
304 views

Has the spin and parity of the Higgs boson been experimentally confirmed? [closed]

I read in a newspaper that the Higgs boson might be the new boson but that this was not confirmed, because we don't know its properties, e.g. its spin or parity. Now I see it confirmed that it is the ...
2
votes
2answers
307 views

Oscillation of a Bose Einstein condensate in a harmonical trap

We were asked to try to make a theoretical description of the following phenomenon: Imagine a 2D Bose Einstein condensate in equilibrium in an harmonical trap with frequency $\omega$. Suddenly the ...
0
votes
3answers
133 views

rotating an object without changing its orientation [closed]

I have a link hinged at one end and attached to a rectangular object via another hinge in the other end as shown. Now, I was wondering how would I maintain the orientation of the rectangular object ...
1
vote
5answers
9k views

How can doped semiconductor be neutral?

I have studied about the two types of doping which result in p and n type semiconductors. I also came to know that they are neutral. But, how can it be? Is it that the positive charge(holes) in ...
2
votes
2answers
610 views

How does flux tubes between quarks bind them together?

If you have, say, a proton it has gluon field fluctuations around it. Those flux tubes between the quarks suppresses the gluon field fluctuations and create a true vacuum between them(correct me if ...
0
votes
1answer
1k views

Why is the wave function complex? [duplicate]

Why should an equation (TDSE) in which first time derivative is related to second space derivative have a solution that contains $i$?The wave function is supposed to be complex, but I am unable to ...
2
votes
1answer
633 views

Why is classical physics not valid for a harmonic oscillator in its lowest energy state? [closed]

I am reading Born's interpretation of wave function in quantum physics by Eisberg & Resnick and I am not able to understand this description about comparison between the classical and quantum ...
3
votes
2answers
577 views

Are there critical constants for liquid-solid transition?

I'm aware of the critical constants for gas-liquid transition but is there such constants for liquid-solid transition? Like the maximum temperature above which a liquid cannot be solidified.
0
votes
1answer
406 views

What do subatomic particles look like for a 'speed of light - observer'?

Let's say that an observer is moving with the speed of light relatively to an atom that he wants to look into. He has equipment that precise that he can observe the atom and what is inside. From ...
13
votes
7answers
2k views

How do you prove the second law of thermodynamics from statistical mechanics?

How do you prove the second law of thermodynamics from statistical mechanics? To prove entropy will only increase with time? How to prove? Please guide.
7
votes
2answers
2k views

Why do clouds appear black?

I have noticed clouds appearing black during rain. But I don't know what makes clouds to acquire that colour. This phenomenon doesn't appear every rainfall. There has to be distinction to white ...
1
vote
0answers
52 views

Estimating the Hubble constant of Virgo Cluster questions?

Im estimating the $H_0$ (Hubble constant) using the calculated distance to galaxy (M100) in the Virgo cluster, but given that the cluster is about 1-2 megaparcecs in diameter, what issues can I expect ...
6
votes
1answer
493 views

Why can we skate on ice? [duplicate]

I have known the reason why skate can slide over ice is that water's melting curve in terms of pressure and temperature has a negative slope. If the pressure due to our mass increases sufficiently ...
1
vote
1answer
2k views

General Relativity: Christoffel symbol identity

I want to show that $$\Gamma ^{\mu}_{\mu \nu}=\partial _\nu (\ln \sqrt{|g|}) .$$ (Here $|g|$ denotes the determinant of the metric.) Working out the left hand side:\begin{align} \Gamma ^{\mu}_{\mu ...
12
votes
1answer
1k views

Can a free particle absorb/emit photons?

As simple as in the title.. I would like to know also some mathematics about it!
1
vote
1answer
377 views

Negligible Mass String

I've recently been working through a lot of physics problems and a lot of them say to assume that the mass of the string used in a problem involving a pulley, for example, is negligible. Why is this ...
0
votes
2answers
570 views

Which is more characteristic of an element absorption or emission spectrum?

Absorption and emission spectrum are used to reveal the identity of an element and even to find new elements. But, which of them is more characteristic? The mission spectrum would have more lines ...
0
votes
1answer
105 views

Is projectile trajectory on Earth affected by the fact that it isn't a singular point?

So in high school physics, we were told that projectiles traveled in a parabola, but Google searches have said that it's more like an ellipse, since the Earth isn't flat. However, I was thinking that ...
-1
votes
1answer
125 views

does the current's direction on a loop with a magnetic field affect the torque?

I have a question in my book The question is very easy, but then my solutions manual gave me unexpected answers I don't get how in d) they conclude the vectors go in the opposite direction, but ...
1
vote
1answer
280 views

Thin lens formula workout method (Query)

In order to workout the method for establishing the formula of thin lens, my teacher says that the optical path is: $PA + AQ = PS_1 + nS_1S_2 + S_2Q$ ($n$ is the refractive index of the ...
9
votes
2answers
1k views

Diffeomorphism Invariance of General Relativity

I'm sorry I know this has been asked before, but I'm still a bit confused. I understand that an active diffeomorphism $\varphi:M\to M$ can be equivalently viewed as a coordinate transformation so that ...
2
votes
1answer
2k views

Calculating Rotational Inertia Using Parallel Axis Theorem

I am working on the following physics problem and have run into some trouble The figure above shows particles $1$ and $2$, each of mass $m$, attached to the ends of a rigid massless rod of ...

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