1
vote
0answers
4 views

Half deflection in a galvanometer

Why is half deflection taken while measuring the resistance of a galvanometer? Can't we take deflection in other ratios? Please help.
1
vote
0answers
4 views

Cardy counting for time dependent theories

In certain limits of 2 dimensional CFT's, it is possible to compute the entropy of the theory in terms of the density of states which is given by the Cardy formula $$S = 2\pi \left(\sqrt{\frac{c_R ...
-3
votes
0answers
12 views

Rest mass of particle of light

in einstien equation of rest mass if we write c in place of v for a particle of light then its mass becomes infinite,is it possible that a object have infinite mass.Explain?
1
vote
0answers
12 views

damped quantum harmonic oscillator - evolution of coherent state

I am trying to solve the following Master equation (also similar to damped quantum harmonic oscillator): $$\frac{d\hat{\rho}}{dt} = \frac{\Gamma}{2}\left(2\hat{a}\hat{\rho}\hat{a}^{\dagger} - ...
1
vote
0answers
12 views

Importance of CP violation

To explain the matter-antimatter assymmetry, CP should be violated according to Sakharov conditions. Charge conjugation is required as matter and antimatter have opposite charges but why Parity ...
1
vote
0answers
17 views

Elastic collision / relative velocity problem

I'm having some trouble with a homework exercise and I'd really appreciate some help! I've done the first part correctly (according to the solution sheet), but I can't seem to get the second part ...
0
votes
2answers
17 views

Helical motion of charged particle in external magnetic field

When an electron moves in uniform external magnetic field, with velocity not perpendicular, I understand that the magnitude of force is only due to the perpendicular component of velocity and is ...
1
vote
0answers
17 views

Normalizing ket vectors

So I've run in to a bit of a notation problem on my coursework I have a vector, |A> expressed in the orthogonal basis |1> and |2> |A> = |1> + i |2> I need to convert it into bra form to normalize ...
1
vote
0answers
20 views

What am I doing wrong while proving time dilation using Minkowski space-time diagram?

Consider two events A and C. They have same value of x' and time interval between them is $\triangle \tau$. This is the proper time interval between the events. ...
0
votes
1answer
22 views

Is light relative?

I was wondering, if two cars (A and B) are going at different velocities let's say A=90km/h, B=80km/h then if we add the two speeds we get 170km/h meaning they are relative to each other. But if one ...
4
votes
1answer
31 views

Fundamental forces

I read @ http://m.particleadventure.org/electroweak.html Physicists concluded that, in fact, the weak and electromagnetic forces have essentially equal strengths. This is because the strength of the ...
-3
votes
0answers
20 views

De-broglie wavelength

The de-broglie wavelength of an electron emitted from the ground state of an H-atom after the absorption of a photon equals 1/2 of the de-broglie wavelength when it is in orbit. The energy of the ...
2
votes
3answers
25 views

How can “…electrons flow in metals, but not in the ground…” explain grounding rods?

I really enjoyed Why is the charge naming convention wrong? But, in the comments at the very end, the statement that "...electrons flow in metals, but not in the ground..." left me uneasy. I was ...
1
vote
2answers
31 views

How does a point charge interact with a Gaussian surface?

A spherical Gaussian surface encloses a point charge $q$. The point charge is moved to to a point away from the center of the sphere. Does the electric field at a point on the surface change? ...
0
votes
2answers
34 views

How to show state functions are perfect differentials, or vice-versa?

Suppose a variable $z$ is a function of two independent variables $x$ and $y$. Now, if z can be expressed in its total differential form as $$dz=Mdx+Ndy$$ Then show that $z$ is a state function iff ...
1
vote
0answers
11 views

Derived Geometry and Deformation Quantization

Can anyone please explain to me in layman' terms what derived geometry deals with and what deformation Quantization is? I have only a good understanding of Relativity,Classical Mechanics.
1
vote
1answer
22 views

Magnetic field in two different medium

From Faraday's law of induction we know if we have a coil with ac current it will create ac current to other coil placed within magnetic field. My question is if one coil is in water and another coil ...
1
vote
1answer
20 views

Calculation Equivalent Resistance In A Circuit With resistances connected in a circle

I am having trouble in finding the equivalent resistance between the terminals 'a' and 'b' in the following circuit: Please can anyone explain to me how to solve such problems. Thank You!
0
votes
0answers
17 views

Why do we see discrete light spikes coming out from a light source?

When we look at a light source from a distance in suitable darkness, why do we see discrete light spikes coming out of source like Fig. b of above picture instead of Fig. a?
0
votes
2answers
32 views

The Vectors in $v=f\lambda$

We are learning about waves in physics and I was just wondering what are the vectors and what are the scalars in this function:$$v=f\lambda$$ I know the velocity $v$ is a vector so that means that: ...
1
vote
1answer
16 views

In 2D CFT, is there a name for a field with the following OPE?

A primary field $\mathcal{O}(w,\bar{w})$ with weight $(h,\bar{h})$ has the following OPEs with the stress tensor: $T(z)\mathcal{O}(w,\bar{w})=\frac{h\mathcal{O}}{(z-w)^2}+\frac{\partial ...
1
vote
0answers
14 views

How can you find the $u$ using time dilation if you only know $\Delta t_o$?

I've come across two problems dealing with time dilation now that ask how fast should an astronaut go in order to travel EG: 400 LYears in 10 Years. What I can not wrap my head around is how this is ...
1
vote
1answer
19 views

A couple of questions regarding work to velocity exchange

I was tasked to express the velocity of the cube of mass $m$ at point B using the constants given in the picture below. Friction could be ignored, and the cube could be presumed to reach B with the ...
0
votes
1answer
20 views

Relation between homotopy theory and symmetry transformation of the Lagrangian

What is the relation between the symmetry transformations of the Lagrangian and homotopy theory? If yes, how? Not sure if this is a math or physics questions. References would be very helpful.
0
votes
1answer
18 views

Magnetic field of a current carrying wire reduce/increase exterior magnetic field?

If we place a wire within a uniform exterior magnetic field ($B_x$) that's perpendicular to it's length, and allowed current to flow withing the that conductive medium, there is another magnetic field ...
0
votes
2answers
39 views

Is the video “How to Reveal Subatomic Particles at Home”'s explanation of its experiment misleading?

https://www.youtube.com/watch?v=wN_DMMQEhfQ The video asserts that along the path of an electron or muon, a trail of condensation will appear. But from what I understand, if an electron or muon (both ...
0
votes
0answers
26 views

Undergraduate Physics Senior Research Topic (Theory/Mathematical Physics Based)

This is most likely a question for those who have experience/knowledge of theoretical/mathematical physics at the graduate level and can provide recommendations following my criteria. Here is some ...
1
vote
2answers
12 views

Why is the electric potential of a point from a point charge of +Q positive?

According to the formula, V = - integral E dot product dr The electric potential of a point charge is KQ/R? However, when I perform the integration, my answer is -KQ/R. Since the direction of the ...
-3
votes
2answers
19 views

Problem - Escalator [on hold]

I need help in resolving the following problem: On a recent weekend, Anna was rushing through a shopping centre doing her shopping she had occasion to use the escalator 3 times. The first time the ...
1
vote
0answers
14 views

ferromagnetic and Curie temperature. Energy question

Is energy absorb and release back when a ferromagnetic material heats and cools passing through the Curie temperature?
1
vote
1answer
30 views

Energy of electromagnetic wave

Its given here that energy density of an electromagnetic wave is $$\vec S=\frac{1}{\mu}(\vec E\times\vec B)$$ How is the above expression derived? And when did energy become a vector? I though work ...
1
vote
2answers
17 views

Why use vectors to describe velocity/force/etc instead of treating magnitude and direction as separate values?

I'm only 4 weeks into my first college-level physics course, so this is a very elementary question. Also, in asking this question, I'm just playing devil's advocate in order to better understand the ...
0
votes
2answers
64 views

How can space and time occur spontaneously?

In the book: "A universe from nothing" by the theoretical physicist Lawrence Krauss he mentions that space and time can occur spontaneously. Unfortunately he does not explain how. So my question is, ...
4
votes
2answers
26 views

Acceleration of a car on Earth and on the Moon

Suppposing the same enviroment conditions and without considering the air friction a car at the start of a race would have a greater acceleration on Earth or on the Moon, or would the accelerations be ...
-2
votes
1answer
57 views

Is climate change caused by humans? [on hold]

Some people argue it is not because it is caused by solar cycles (sometimes the sun brights more than others thus increasing the Earth's temperature) and that the energy that $CO_2$ traps isn't enough ...
-2
votes
1answer
38 views

Bohr radius question

I'm doing a homework problem where it asks to calculate the diameter of a hydrogen atom with $n=600$. I used the equation $r=\frac{n^2a_0}{Z}$ where $a_0=0.529e^{-10}m$. Solving for $r$ yields: ...
-1
votes
1answer
20 views

Where are the electron exchanges happening in solar cell physics when considering the photon?

When considering solar panel physics, are we taking an electron from Light(photon), or is the energy of Light causing an electron to jump in said solar cells through excitation? Is the photon even ...
1
vote
0answers
16 views

Quantum GCD circuit: Clearing ancillae

I am currently trying to implement a circuit for computing the greatest common divisor in the Quantum Computing Language. In my work, I partially proceed from the paper Quantum Circuits for GCD ...
-1
votes
1answer
26 views

The question of the protein and the ribosome

It is well known that proteins are spit out by ribosomes by reading the DNA that goes in. Now ribosomes are made of proteins. Doesn´t this mean that the riobosome structure came before the production ...
1
vote
0answers
22 views

Relativity Mapmaking in spacetime

The problem as stated: I do not know how I am supposed to map this. The instructions don't make sense to me and the textbook is really un-helpful. This is the map that I have to draw this on. I ...
0
votes
0answers
7 views

Black hole starship: Would micro black-hole Hawking radiation emit anti-matter?

My understanding of Hawking radiation is that virtual particle pairs of matter and anti-matter are created from vacuum energy and one of those virtual particles may escape while the other enters the ...
0
votes
1answer
34 views

Light is/produces a electromagnetic wave, but is the opposite also true?

A similar question has been asked, and to some extent the answer is: you need an antenna with $L \approx 200nm$. But it's not entirely clear to me if this is completely hypothetical, as "Marek" also ...
0
votes
3answers
38 views

How do free electrons conduct heat in a metal?

In a metal, how do free electrons conduct heat? Does the specific heat of a metal should be then related to the electrons and not the atom of the metal?
0
votes
0answers
40 views

On the Pauli Principle

Consider a quantum mechanical system as shown-say a piece of metallic conductor in the shape of a long, thin bar.(Must it be a single crystal to be considered a "system"?). Now focus on two free ...
0
votes
1answer
14 views

Simple Harmonic Motion given velocity and acceleration

I am trying to understand how to relate velocity and acceleration of an object to it's amplitude, period, and frequency given only the following: An object of mass m=20kg moves with SHM along the ...
0
votes
0answers
13 views

finding work done by the buoyant force on a submerged object [on hold]

A flotation device is in the shape of a right cylinder, with a height of 0.500 m and a face area of 4.00 m2 on top and bottom, and its density is 0.320 times that of fresh water. It is initially held ...
1
vote
2answers
37 views

How is refractive index related to the density of a medium (for example, air)?

I have a question regarding refractive index dependency on the density of a dielectric, specifically air. Background Let us start from Newton's second law form of driven harmonic oscillators ...
1
vote
0answers
23 views

Does a set of eigenvalues in QM correspond to a random variable in statistics? [duplicate]

In quantum mechanics the possible outcomes of a measurement of a quantity corresponding to a linear hermitian operator $A$ are only the eigenvalues $a_i$ of $A$ (see e.g. ...
2
votes
0answers
25 views

Decoherence and interpretations

With quantum decoherence, are there still any "gaps" in our knowledge of quantum mechanics that hint (either in terms of the physics, philosophy, or otherwise) at the need for further interpretation? ...

15 30 50 per page