# All Questions

21 views

### How to derive De Haas–van Alphen effect?

I was reading Solid State Physics by Kittel and they manage to derive De Haas–van Alphen effect by invoking the Bohr-Sommerfeld model. This feels unsatisfactory to me. Can someone derive this using ...
44 views

### How did the scientists discover that antimatter exists? [on hold]

How did the scientists discover antimatter? I'd like to know the process of that discovery.
116 views

### Group theoretic way to find charges after SSB

I was wondering what is the group theoretic way to find the resulting charges of matter fields after a scalar field is given a vev. In the case of the EW symmetry breaking, one can directly read the ...
40 views

### The ADM Energy of Gravitational Waves?

I have been looking for books about this question for several days. However, almost all books use Landau–Lifshitz pseudotensor to calculate the energy of Gravitational Waves.And they said the result ...
19 views

This is from Griffith's "Introduction to Electrodynamics" 4th edition, problem 5.33. I need to show that $$\tag 1 \frac{\partial \textbf{A}_{above}}{\partial n}-\frac{\partial ... 2answers 61 views ### When are infinities okay? I'm a little confused about how to handle infinities in physics. On the one hand, I always here things like infinities are not physically tenable answers. GR can't answer anything about the origin of ... 2answers 37 views ### Which will collide first, the moon and Earth, or Sun and Earth? As time progresses, which scenario will happen first? The moon colliding with Earth, or the Earth colliding with the Sun? I figure the Moon and Earth will happen first, based on proximity, but the sun ... 1answer 24 views ### How I can solve this ? (kirchhoff's law) Plz discuss it to me [on hold] the remaining of question is ( careful choice of suitable loop can make it easier ? i choose outer loop and answer it like that: 10 Volt = ( I X 10 ohm ) + ( I X 10 ohm) but it give wrong answer ... 0answers 84 views +50 ### Supersymmetric cancellation of loop contributions in a SUSY gauge theory It is known that in SUSY models, loop contributions are automatically zero leading to a technically natural solution of the Higgs mass hierarchy problem. In many SUSY books/notes, it is often shown ... 0answers 35 views ### Flow rate of water in a gutter system [migrated] I am attempting to build a waterfall out of a gutter system. I currently have an awning that is 72" by 48" with 3" high (tentatively) buffers on each side to keep the water from flowing off. The ... 1answer 144 views ### Stern Gerlach with spin in opposite directions So for the Stern-Gerlach apparatus, we assume that we either have a particle spin up or spin down. We also have the varying field, \partial B/\partial z. This initial configuration results in the ... 0answers 8 views ### Determination of “Heat transfer coefficient” between block of aluminium and air I need to build a temperature control system for a hot plate of aluminium, which I intend to heat with an electric cartridge, and the temperature I would be measuring with a PT100 to close the loop. ... 4answers 172 views ### Is nature quantized? I was reading Planck's postulate the other day on Wikipedia and couldn't help but noticing the sentence: "...is the postulate that the energy of oscillators in a black body is quantized..." ... 1answer 83 views ### Figuring out the time period of an Atwood system SO I was working on Atwoods, when I came up with the following problem, It is more complicated but i should understand this simpler scenario first. As shown in the diagram above, (Atwood machine), ... 1answer 19 views ### Faraday's electromagnetic induction Does the emf increase when no of turns of the same wire increased? Consider a wire of length 'l' is coiled with an area of cross section 'A' is subjected to a change in magnetic flux. an emf will be ... 0answers 14 views ### A question on average velocity [on hold] Two different books have two different answers. one says option a and one says option b. Which one is correct? 3answers 129 views ### What are correlated magnetic moments? My book has the following sentence and I don't understand what correlation or lack of correlation means: At high temperature the magnetic moments of adjacent atoms are uncorrelated (to maximize ... 1answer 81 views ### Question about Hartle and Hawking's universal wavefunction? My apologies in advance if this question is poorly worded or doesn't make any sense, however I have just finished reading into this theory and it seems as though Hawkings No Boundary Universe is ... 0answers 15 views ### Book recommendation for atomic & molecular physics What are some wonderful books about modern physics for a sophomore undergrad to learn atomic & molecular physics? Some easygoing books for a start up would go well. 2answers 42 views ### Eigenstate vs collapsed wave function An eigenstate, or determinate state, is a state where the measurement of some observable always yields the same result. This means that the standard deviation of the observable is zero. If a ... 2answers 77 views ### How do you rotate spin of an electron? I can't seem to connect these two stories. Can you please help? I have heard that you have to turn electron by 720 degrees in order to get the same spin state. Has this been seen experimentally? How ... 2answers 960 views ### Is Palladium an exception? I have been taught in school that atoms cannot have more than 8 electrons in the outer shell. Palladium atom's electron configuration is 2,8,18,18. Why isn't it 2,8,18,17,1 like the case of Platinum ... 5answers 2k views ### Can you put a magnetic ball into a hollow magnetic sphere? if all magnets have to have two poles(one north one south), is it possible to construct a hollow sphere where the inside face of the sphere was one pole, and the outside face another pole? is it also ... 2answers 148 views ### Why does a magnetic field raise the ground state energy of an electrical particle? I heard a statement that the ground state energy of a electrical particle in a magnetic field is larger than its ground state energy without the magnetic field. I just heard this statement. This ... 3answers 629 views ### Do objects sink in ice? The title explains it all. Do objects suspended in ice sink over time? You may remember the story of World War 2 planes that were found 260 ft under the ice which would be anachronistic with seasonal ... 0answers 26 views ### A strange (poisson?) standard deviation for multiple measurements in experiments When doing error propagation, in the variance formula, I use standard deviation for si, as I was taught in experimental physics courses. However, a friend of mine was taught a different method, he ... 2answers 48 views ### With what initial speed does the person leave the ground to reach a height of 60 cm? [on hold] An average person can reach a maximum height of about 60 cm when jumping straight up from a crouched position. During the jump itself, the person's body from the knees up typically rises a distance of ... 1answer 94 views ### Why is voltage added when batteries are connected in series but not in parallel? As I understand, the different voltage between two object is caused by the total different charged between two object. Thus, the higher extra electron between two opposite charged object, the higher ... 0answers 39 views ### Interstellar Movie: Black hole shown in the movie [duplicate] In the interstellar movie, the black hole shown has a ring of light orbiting around it. From what I know, (correct me if I'm wrong) that light is unable to escape the gravity of the blackhole and ... 0answers 10 views ### Transistor as Oscillator [migrated] While I was studying the use of Transistor as an Oscillator from my Fundamentals Of Physics By Halliday, Resnick and Walker , I faced several confusions. My book says that when the switch S1 is ... 2answers 636 views ### Why does the Standard Model predict Neutrinos are massless? Why are neutrinos massless in the Standard Model? Is it connected with experimental fact that neutrinos always have only one direction of projection of spin on motion direction? 6answers 128 views ### Confused about Lorentz contraction My son asked me the following question which I can't answer in a simple way. A frame O' has speed v relative to O. A photon travelling along the x'-axis in frame O' over a distance L' ... 1answer 93 views ### Unknown magnetic moment of orthohydrogen Conforming to present atomic physics, the two elementary particles in hydrogen atoms can have either parallel or antiparallel magnetic moments, and the energy differences between these two kinds of ... 1answer 400 views ### Is sound considered a subtopic of physics? What are the SI units of sound? Does physics cover sound? If so, why does sound not have units in the SI system, or how would we measure sounds and frequency? I guess it's debatable, but why isn't it standard practice in physics? 1answer 487 views ### Comparison between isobaric, isothermal and adiabatic expansion Please check if my understandings of these terms are right because they are a bit confusing to me. For all three types of expansions, a change in volume means work is done by the system to the ... 0answers 23 views ### SUSY preserved by an extended D-brane There's a nice way to prove that for an extended D-brane half of SUSY is preserved, from perturbative string argument with SUSY Ward identities and the doubling trick (at least, at tree-level and ... 2answers 55 views ### Understanding colored shadows When I turn on white lights, these chairs cast a shadow. However, when blue LED lights are turned on the shadow turns yellow. Why is this? Is this due to interference of light or is it just an ... 1answer 64 views ### Leptogenesis with singlet neutrinos (i) The Lagrangian of electroweak model extended with right-chiral singlet neutrinos N_{iR} contains the Yukawa coupling term+ the bare Majorana mass term$$f_{\alpha ...
19 views

Tadpole-free is a very important condition for perturbative string theory (which is equivalent to the theory to be expanded around the "right" vacuum). For simplicity, let's consider closed string ...
26 views

### An interesting question on the mass of a droplet of liquid experiencing the Leidenfrost Effect

Background and Inspiration: I have seen numerous demonstrations of the leidenfrost effect, both on the internet and in my mother's kitchen. But I started wondering about a general case after having a ...
57 views

### $U(1)$ 5-dimensional Kaluza-Klein topological defects

Five-dimensional Kaluza-Klein theory is well-known to predict that the electromagnetic field can be described as a curled additional dimension over four-dimensional spacetime. That is, you only need ...
40 views

### Why do we define the magnetic field around a conducting rod as concentric instead of radial?

Why is it that we define the magnetic field around a conducting rod as concentric instead of being radially outwards? Ok, we know from the Lorentz force law, that the magnetic force is the cross ...
45 views

### Why does a non-contact voltage detector light up when you touch a plasma ball with the other hand?

I am doing a science experiment and we decided to try holding a non-contact voltage detector up to plasma ball. We were surprised that it would light up when it was 3 ft away from the plasma ball. I ...
60 views

### In what direction will this magnet move? [on hold]

What will be the direction movement of small ringshaped magnet when place inside the big ringshaped magnet with the same poles?
441 views

### Dielectric slab counter-intuitive formula?

For the calculation of force on one of the two equal(in magnitude, opposite in sign) point charges separated by $r$ with a dielectric slab of dielectric constant $K$ and width $d$ in between, the ...
27 views

### Is it possible to use hot cloudy water as a cloud chamber?

This morning I got some warm water from the shower head to a dark plastic basin to wash some sensitive clothes. During the process lots of tiny bubbles got into the water so it had a cloudy ...
27 views

### Observed speed of light [duplicate]

Suppose two very fast trains, train $A$ traveling a constant speed of $.5c$ and train $B$ traveling at a constant speed $.75c$, are on the same straight track heading straight towards one another. If ...
80 views

### Particles that are distinguishable and indistiguishable at the same time

Thinking about a question and my answer to it and another question I asked earlier. I've come up with the following problem: Consider two otherwise very similar marbles, a red one and a blue one. Let ...