instruction stringlengths 31 24.3k |
|---|
I mean what actually happens so that sound can vibrate an object? If both frequencies are subjected to constructive interference then resonance, why doesn't the sound only increase in amplitude rather than vibrate the object it is exposed to?
I read some articles, it just says that both the frequency of sound and objec... |
In what way can I see the rotating hub and the bullet that has just been fired clearly with the naked eye? Some people say that you can place a shutter in front of your eyes, and then adjust the shutter to a suitable speed. Is this method feasible?
|
Imagine I am inside a lake of ideal incompressible, non-viscous fluid. I have a hollow frustrum-like structure with both ends open, basically a tube with one end of a larger radius than the other.
I throw it with some velocity $v$, with the larger opening facing forwards. Now, from the frame of reference of the frustru... |
I have read from a few sources that cylindrical waves propagate leaving a wake behind, differently from spherical and planar waves, which would propagate sharply, ‘cleanly’.
One example is this question and its comments. One reads:
“The wave equation may allow any shape wave front, but Huygens principle does not hold f... |
I found this concept of entropy production in wikipedia.
Mainly I am trying to figure out the formula the Clausius formula for entropy production. What exactly are the terms involved?
For what process is $S-S_o$ written?
For what process is $\int \frac{dQ}{T}$ written? What is the $T$ in this expression?
|
Frictionless surface
$$I_0 = Icm + MD^2.$$
Also, if it does, the coin will fall down thus changing the cm. Will this affect the inertia? or must i use parallel axis theorem?
|
What is the minimum force that we need to lift our body to walk up a flight of stairs?
Let's say I weigh 50 kg and I walk up a flight of stairs. What the minimum force I need to apply to stand straight on flat ground and to climb the stairs?
|
Just like Quantum Mechanics has many interpretations (Copenhagen, Many-Worlds etc.), do any other theories in Physics have multiple interpretations? For example, does Classical Mechanics, Classical Electrodynamics, Special Relativity, or General Relativity have multiple interpretations?
|
In this paper (Erickson et al, 2000), the authors claim in eq. (46) that the Green's equation corresponding to a bosonic propagator $\Delta(x)$ in $2\omega$ dimensions is:
$$ - \partial^2 \Delta(x) = \delta^{2\omega} (x). \tag{1}$$
But why is there a minus sign in front? If I am not mistaken, the Green's equation in fl... |
Could you please argue with work and gravity? Or however you like. I just don't get it. Thanks.
A physics professor talked about if light had a mass, it should do work ($W=N\cdot m = \frac{kg\cdot m}{s^2}\cdot m$) to get out of the gravitational field. But because we somehow can see it doesn't, light doesn't have a mas... |
In Fluctuation-induced current from freestanding graphene (peer-reviewed version on Phys. Rev. E, note: behind a paywall) Thiabado, et al, report the extraction of work from brownian motion. The experimental set up involves graphene in close but insulated contact with an electrode that charges a battery and a storage ... |
We have virtual particles in quantum field theory (QFT). In general, they don't have the need to obey causality.
My question is:
Do the processes in QFT (electron self-energy, photon self-energy, electron-photon vertex, etc.) have to obey causality?
For example, can some parts of the electron self-energy diagram fall o... |
There is something I don't understand about the units of unified atomic mass.
I have seen on Khan Academy that $1$ unified atomic mass ($u$) is equal to $1.6605\times 10^{-27}$ kg.
But after 2 videos he writes that the unit of $u$ is $\frac{\mathrm{g}}{\mathrm{mol}}$. Why is it true?
Why I can say that according to tab... |
In an attempt to predict the outcome of a toss, I dropped a coin with its edge just touching another sharp edge as shown in figure. (The edge is flat and sharp with very less friction as in case of a blade)
I expected the calculations to be simple but it doesn't seem so.
The main issue is in finding the angle at which... |
If the proton were a point charge like the muon, then $ep\to ep$ scattering, the differential scattering crossection is $$\frac{d\sigma}{d\Omega}\Bigg|_{\rm lab}=\Bigg(\frac{\alpha^2}{4E^2\sin^4(\theta/2)}\Bigg)\Bigg\{1+\frac{2E}{m_p}\sin^2\theta\Bigg\}^{-1}\Bigg[\cos^2(\theta/2)-\frac{q^2}{2m^2_p}\sin^2(\theta/2)\Bigg... |
What's the best slab of stone to place under electronic devices to keep them cool?
Each stone has its own thermal profile which includes its thermal diffusivity, thermal conductivity, and thermal inertia. But I don't know which combination of thermal properties a stone should have to be a good candidate for placing und... |
The entropy of a system of an ideal gas depends on the external parameters $U, V, N$.
I always thought entropy is defined by a certain macrostate, which is a set of given external conditions like fixed $U,V,N$. This is one defined macrostate. The macrostate is the framework for a certain amount of accessible microstate... |
is it possible to talk about how much extra range a ballistic missile gets if its warhead were to shrink by say 10x?? that is without knowing other details about the missile. For example: Iran claims they have ballistic missiles that can carry a 1500kg warhead up to 2000 KMs.
if the warhead weight were to be reduced to... |
The objective of this problem was to find a $K$ such that as $T$ changes with $V$ for an adiabatic, reversible (isentropic) process for a real gas, we get the equation
$$T_2 \approx T_1 \exp(K\Delta V)$$
So this is procedure I followed,
$$dT = \left(\frac{\partial T}{\partial V}\right)_S dV + \left(\frac{\partial T}{\p... |
As I have understood, as per QM, electrons could behave as waves in a double slit experiment, i.e. form dark and bright bands, albeit after sufficient electrons have been shot from the source. Also, I have come to see that gaining information about the "Which slit has the electron passed?" messes up with the original p... |
We know the composition of stars by spectroscopic analysis. The EM waves generated by them are blue- or redshifted. We could have said, "Look, the wavelength is slightly different so it may be constituted of quarks and leptons which are slightly different than ours."
How do we ascertain that it is made up of the same p... |
Lets assume there are particles with mass. If the mass is big enough, they will accelerate toward the center of mass. Thus the particles gain kinetic energy and hence the total mass gets bigger. Since the radius of particle system decreases and the total mass increases, the curvature of spacetime will grow. So what I w... |
Consider the wave equation in 1 spatial dimension (in units where $c=1$)
$$
\frac{\partial^2 u(t,x)}{\partial t^2} - \frac{\partial^2 u(t,x)}{\partial x^2} = 0 \ .
$$
Now suppose that the solution is $u(t,x)=0$ for all $t<0$. Then suddenly at $t=0$ a boundary condition gets enforced at $x=x_0$
$$
u(x_0, t) = \Theta(t) ... |
The definition that I have concluded is that:
No two fermions can exist in the state, or quantum state, unless they have opposite spins.
Am I right in saying this? They can have the same azimuthal number, the same principle quantum number, and thus the same magnetic number but if they have a different spin it's alright... |
Okay let’s start straight away, What is Escape Velocity?
Is it the speed required to get into orbit, or
is it the speed required to escape the SOI (Sphere of Influence) of Earth completely?
If it’s the (1) then probably Google is wrong and probably everything else like the ISS is also wrong because according to the... |
Is the normal component of diffusion flux is always continuous? I know the continuity at any surface would mean the amount of fluid that is entering through the surface is the same amount that is going out. If the normal component of the diffusion flux is discontinuous, what would be a physical interpretation of that?
|
Say we have a vector function $\vec{D}$ defined in some region on whose boundary its divergence goes to infinity and inside we have $\nabla \cdot \vec{D}=\rho$.
Then is it valid to use the Gauss divergence theorem here? That is can we say :
$\int_{V}(\nabla \cdot \vec{D}) d v=\int_{V} \rho d v$ , hence
$\int_{s}\vec D\... |
In this article I found an interesting remark on how group (representation) theory was introduced into the physical sciences :
Murray Gell-Mann developed the “eight-fold way” to explain the spectrum of hadrons in the 1960s. It wasn’t until after he’d developed this formalism that he discussed his model with mathematic... |
Mathematically, it is obvious that the total orbital angular momentum $L^2$ commutes with the spin-orbit Hamiltonian $\propto\boldsymbol{L}\cdot\boldsymbol{S}$. However, is there an intuitive physical reason for this?
For example, the total angular momentum $J^2$ must commute because there is no external torque, and th... |
I am currently studying Optics, fifth edition, by Hecht. Chapter 2.11 Twisted Light says the following:
Such beams have what’s called an azimuthal ($\phi$) phase dependence. Looking down the central axis toward the source the phase changes with angle, just as the time on a clock face changes with the angle $\phi$ bet... |
In a LED the electrons in the n-type move to the p-type where they are then 'combined' with the holes in the valence shell of the p-type which produces photons. My question is that when this happens are the electrons gone or have disappeared?
Also do the electrons 'run out' in this process because they are being used u... |
As a matter of fact, I recently learnt that as an object is approaching a black hole, to an outside observer the object seems to be getting slower and slower and will cross the event horizon after an infinite amount of time ie will not cross the horizon. Now this matter which the observer was observing seems to be stop... |
A cylinder is close at both ends and has thermally insulating walls. It is divided into two compartments by a perfectly thermal insulating partition that is perpendicular to the axis of the cylinder. Each compartment contains 1.00 mol of oxygen, which behave as an ideal gas with $\gamma=1.4$. Initially the two compartm... |
I know that one can increase proton number of an atomic nucleus by proton bombardment as Cockroft and Walton bombarded elements with protons and managed to increase the atomic number. However, how can we decrease the proton number of an element? Can we do it by electron bombardment? Are there any references for this pr... |
I am currently studying Optics, fifth edition, by Hecht. Chapter 2.11 Twisted Light says the following:
Such beams have what’s called an azimuthal ($\phi$) phase dependence. Looking down the central axis toward the source the phase changes with angle, just as the time on a clock face changes with the angle $\phi$ bet... |
My question concerns the commutation rules between bosonic fields operators in the case in which the bosons can assume only discrete positions.
I have organised this post in two sections, in the INTRODUCTION section I will explain the context in which the question arises, and in the QUESTION section the actual question... |
The flavor quantum numbers and charge of $Z$ bosons should allow it to mediate between electrons without violating any conservation rules. So at very short displacement scales do electrons actually attract each other through mediating $Z$ bosons?
|
I have a question about understanding photon emission from a quantum mechanical point of view. I'll give it in terms of experiment to keep things clearer and concrete.
Consider a Van de Graaff generator, we charge it up and disconnect it so we simply have a large object carrying a lot of charge. We then surround the ge... |
I am starting with general relativity and the notation is making me suffer.
If we have, for example, the tensorial equation:
\begin{equation}
A^{\mu\nu} = K^{\mu\nu}
\end{equation}
Where $A$ and $K$ are two arbitrary rank 2 tensors, does this equation imply the following?
\begin{equation}
A_{\mu\nu} = K_{\mu\nu}
\end{e... |
There is something that does not make sense to me regarding a derivation that I am reading of the Planck distribution for black body radiation emitted from a cavity. It treats the photons as particles, uses the 3D wave equation (from Maxwell's equation reasonable as photons are exclamations in the quantum field) applie... |
This research from the University of Arkansas claims to harvest electrical energy from thermal vibrations in a sheet of graphene:
The idea of harvesting energy from graphene is controversial because it refutes physicist Richard Feynman's well-known assertion that the thermal motion of atoms, known as Brownian motion, ... |
The power of a given reactor for the Tchernobyl plant is, according to Wikipedia : 3200 MW (12800 /4 reactors)
Reference :
https://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant
"Reactors 4"
"Thermal capacity 12,800 MW"
Why is the corresponding French Wikipedia stating the the power is of 1000 MW ?
Reference :... |
It is a well known fact that we can bend flowing water with static electricity. However, I am trying to figure out if this is the case for the water vapor as well, and if yes or not why. My professor thinks it is possible though the vapor particles touching the static electricity source would get charged and fly back r... |
When you add electrons to an insulator the electrons stay where you place them and are unable to move whereas in a conductor they repel each other and move to the edges. Why don't the charges just transfer to the ground?
My second question is when you add excess electrons to an insulator they stay where they are and do... |
In Arnolds book in the section of dimensional analysis he tells to show that in a homogeneous central force field (i.e $U(ar) = a^v U(r)$ for some fixed $v$ and any $a$), if $r$ is an orbit, then for any $a$ so is $ar$.
This is easily done via showing that if $r(t)$ is a path, so is $s(t)=a\times r(a^{\frac{v-2}{2}}t)$... |
Given a Hilbert space $\mathcal{H}$, we pick up some state vector $| \psi\rangle$ which lives in the Hilbert space $\mathcal{H}$.
The $| \psi\rangle$ is a vector of the Hilbert space satisfies the rule like
$\langle\psi| \psi\rangle =1$.
My question is about when a Hilbert space's state vector $| \psi\rangle$ can beco... |
I am dealing with a higher derivative theory problem and I have to perform the following integral,
\begin{equation}
\int \dfrac{d^3k}{(2\pi)^3}\dfrac{e^{i{\bf k}\cdot {\bf r}}}{k^4}
\end{equation}
This is because i have to solve something like $(\nabla^2)^2f=K\delta^3({\bf r}).$
I know that if the exponent in the denom... |
I'm just learning the Brakets formalisms for QM and I'm having struggles solving a simple problem.
For an harmonic oscillator, particularly Griffiths' Introduction to Quantum Mechanics P3.34:
I want to measure the expected value of momentum $p$ as:
$$\langle p \rangle = \langle \Psi | p | \Psi \rangle$$
considering th... |
[Warning: I'm not a physicist]
Let $A$ and $B$ be microscopic systems, with corresponding Hilbert spaces of state vectors given by $H_A$ and $H_B$ respectively.
Let's say $A$ is in a state $\psi\in H_A$ and $B$ is in a state $\phi\in H_B$, possibly both evolving unitarily in time. When the two systems "interact", a new... |
A train of 10 wagons each having a mass of $4 \times 10^4 kg$. Locomotive has a mass of $2.2 \times 10^5 kg$ and pulls the first wagon with a force of $8\times10^5 N$. What is the tension between the first and the second wagon?
|
"A person skating on a frictionless icy surface is holding a sandbag. The sandbag has a small hole at the bottom, from which the sand starts to leak. As the sand leaks from the sandbag, the speed of the skater..."
The answer was that the speed of the skater stays the same. I thought that the speed of the skater must in... |
I had difficulties to post my question because the system asks me to detail my need more.
Is it necessary?
Doesn't my question make sense?
There is no need to answer, I just want to know if there is an answer to the title question.
|
Consider then the following reasoning:
Schwarzschild Metric describes the spacetime of a black hole. A gravitational collapse is a mechanism to produce Schwarzschild Black Holes. Conversely, a Schwarzschild metric describes exterior spacetime prior the collapse as well.
Now, I read [1] that this reasoning cannot be a... |
Is there an experiment that verifies the quantum state collapse is a physical process or a process of reality? Or the quantum state collapse is just interpretation, but is not a physical process?
|
I am currently on the concept of energy density and storing electric potential energy on the field itself (which is quite a new and cool concept to me). However, I still don’t have a solid grasp on how potential ENERGY is being stored in the first place. I would like to ask for some advice/corrections for my chain of r... |
I need some help resolving the follow problem. I really don't know where to put the "twice as large as the resultant force on Q3" in order to build an equation. What I found till now is that F2,1 is 0.81.
Q2 = 3 Microcoulombs
Q3 = 6 Microcoulombs
The distance between Q2 and Q3 is 2 meters
Q1(+)-------------Q2(+)-------... |
The Hamiltonian $\hat H$ is given by:
$$\hat H=\frac{1}{2}(\hat p^2+\hat q^2)+K(\hat p\hat q+\hat q\hat p)$$
where $K$ is a real constant, in the coordinate space:
$$\hat p=-iℏ\frac{\partial}{\partial q}$$
$$\hat q=q$$
I try to solve it by expanding those operater, and end up with:
$$\hat H=-\frac{ℏ^2}{2}\frac{\partial... |
I'm a beginner studying mechanics for the first time. I am a homeschooler, stuck with an incomplete and vague course textbook, and largely self-taught, so please bear with me; these are painfully basic questions, but I need clarification of concepts.
I've attached an image of the question. It has multiple parts.
My qu... |
As per this Phys.SE post, an active parity transformation is when a particle at $(a,b,c)$ is reflected about origin to move it to $(-a,-b,-c)$. A passive one is when the particle is still at the exact point in space but its position is now described by $(−a,−b,−c)$.
How can these be one and the same (if they are) since... |
Is it possible to create a sonic boom using a specially designed audio device for this purpose?
|
Not much more than what I asked in the title. I think it is true that a moving charge emits photons also.
|
For general gauge theories, the total Lagrangian density is given as $$L=-\frac{1}{4}F^2+L_M(\psi, D\psi)$$ where $L_M(\psi, D\psi)$ is the matter field with the ordinary derivative replaced by the covariant derivative $D$. Here $\psi$ is a generic matter field other than the gauge field.
Then, for calculating the equa... |
When water is flowing from an over head water tank as shown in the associated picture, Would water lose all it's kinetic energy due to friction in pipe and thus stop flowing ,if the pipe is sufficiently long enough or would water flow always irrespective of length of the pipe?(Assume water tank contain more water than... |
Question: A train of length $l=350 metres$ starts moving rectilinearly with the constant acceleration $a=3×10^-² ms^-²$; $t=30s$ after the start the locomotive headlight is switched on $(event 1)$, and $t=60s$ after that event the tail signal light is switched on $(event 2)$. How and what constant velocity $V$ relative... |
In the end of 27 in Srednicki book in QFT https://www.cambridge.org/core/books/quantum-field-theory/718DD037728FB3745F48A40A6D9A8A1C, when he is discussing the case of asymptotically free theory, he gives an expression for the $\beta$-function of $\phi^3$ theory in $D = 6$ dimensions.
$$
\alpha (\mu_2) = \frac{\alpha (... |
I Was re-deriving Hollowood & Kumar paper (here is arXiv link of it) which is about Anti-De Sitter Black-Holes with JT Gravity, anyway I got a problem with solving a schwarzian derivative differential equation in 3.19 of this paper which gives 3.22 solution without much explanation. I would be grateful if you could hel... |
For a physics project I'm changing the temperature of a rubber band and measuring elasticity. The rubber band will be tied to a mass and will be heated in a water bath.
Some sources show data of the rubber band becoming softer and stretchier (there is data of this), whereas others list that the entropic force results i... |
I'm trying to evalueate the magnetic field generated by circular current carrying loop. My manual says that for the symmetry of the sytem only the magnetic field along the $z$ axis (which is the symmetry axis of the conductor) is not zero. I don't understand the reason. It seems that if I consider a point $P$ on the $... |
In a typical modern nuclear plant, there are :
a primary circuit, which allows to transfert the heat of the fission (transfered to the water) to a secondary circuit.
a secondary circuit, which transforms the liquid form of the fluid into steam, used afterwards to create electricity.
a tertiary circuit, which transform... |
10 g of water at 70C is mixed with 5g of water at 30C Find temperature of mixture in equilibrium
I solve this problem by first converting the water at 70C to 40C and using the excess energy to figure out how much the combined water should rise up.
However my book had another approach to it as follows:
$$ Q_{\text{h... |
I'm a student and I'd like to confirm my understanding of Quantum field theory (QFT). QFT says particles are actually excited states in pre-existing fields. Each field is only excited with specific energy value or its integer multiples, so it looks like one or more particles but never half a particle. Every excitation ... |
fairly simple question here: how do we know that the lines of electric force move into a negative charge and out of a positive charge?
Does this have physical significance, is it detectable in an experiment? Or is this simply a convention we use?
Thank you!
|
I recently asked my physics teacher this question, and he could not give me a clear answer:
How gravity acts on a streched rope?
Consider example like this one below: if we strech a rope of mass m between points distance d apart, how low will the rope hang? And what will be the tension on the rope? Is rope a perfect pa... |
Can the $\beta^-$ decay proceed by the absorption of a $W^{+}$ boson or the $\beta^+$ by the absorption of a $W^-$ boson?
The $\beta^-$ decay is known as the decay of a $d$ quark into an $u$ quark and a 'virtual' $W^{-}$ boson, which then decays further into an electron and an electron anti neutrino. Similarly, in the ... |
A high schooler like me asked a question on here regarding the equations used for cantilever deflection, inquiring about derivations. It turns out the derivation is learnt in the first or second year of a phx/engineering degree at university, and also needs an understanding of differential equations which I don't yet h... |
Kepler's third law or periods affirms that:
"The squares of the times that the planets use to cover their orbits are proportional to the cube of their average distances from the Sun".
font from as an example https://it.wikipedia.org/wiki/Leggi_di_Keplero
(the first definition) and
from the English book PHYSICS, Ja... |
How can tin whiskers be produced in an easy way as fast as possible without needing temperatures above 100 °C and in atmospheric pressure?
Metal whiskers grow from bottom and up. It is not a form of deposit on the top from gaseous metals, which some say. The following videos show growth from the bottom and interior.
h... |
body 1 and 2 are pulling the balance by 20 N
what does the balance read?
same question but without 2.
for 1st question I thought the balance will read zero force because they are two opposite forces of the same magnitude but it's wrong. the correct answer is 20N I don't know why
|
From my understanding, little as it may be, because photons have energy they warp spacetime. The energy is expressed as an oscillating electric and magnetic field. Would this mean that the energy is also oscillating and would generate a gravitational wave?
|
As I understand it:
$dS = \frac{1}{T}dU + \frac{p}{T}dV$
(for a thermodynamic system where $dN=0$) and since for an ideal gas $pV=Nk_BT$ and $U=C_VT$ we can say
$dS = \frac{C_V}{U}dU + \frac{Nk_B}{V}dV$
so ultimately entropy changes are caused by changes in proportional changes internal energy $U$ (proportional to the ... |
I'm working on the Conservation Laws in Peskin (page 309), but I was confused for it.
In last section, I know that
Classical: the action is stationary.i.e. $\delta S =0$ when $\phi(x)\rightarrow \phi(x)+\epsilon(x)$, so we obtain Euler-Lagrange equation
Quantum: the generating functional is invariant.i.e. $\delta Z[J... |
I am working on a grand canonical Hamiltonian which has the form:
$$
\hat{K}=\hat{H}_{SC}+\hat{H}_{tip}+\hat{H}_{T}-\mu\hat{N}_{SC}-(\mu+eV)\hat{N}_{tip}
$$
where $\hat{H}_{T}=-t_0\sum_{\sigma}(c^{\dagger}_{r\sigma}\hat{d}_{\sigma}+h.c.)$ is the tunnelling term between the superconducting system and the tip of a scanni... |
According to my physics book, inside a resistanceless battery (it is a part of a closed circuit) the conservative field has the same magnitude but opposite direction to the non conservative field.
Thus $E^* = -E$.
$E^*$ is the non-conservative field.
Anyway, I can apply the Ohm's law to a real battery because a current... |
I want to ask whether mass changes to charge or any other form in beta plus decay or minus decay because in beta plus decay up quark changes to down quark with formation of positron and neutrino, here charges are same on both sides but mass on the right hand size increases than left side. So from where that mass comes ... |
I'm looking for pointers to give me a better understanding as to what 'space' is. I do not mean the descriptions of what's in 'space' i.e. not interested in descriptions of outer space filled with particles and quantum foam. I'm interested in learning more about what the 3D 'shape' is actually made from, so for more ... |
What is the difference between surface plasmon polariton and plasmon in the Hamiltonian? So let's say that I can diagonalize the Hamiltonian of the system I am studying no matter how complicated that is, how do I distinguish a surface plasmon polariton from a bulk plasmon without plotting the charge of the wavefunction... |
I read some books and some articles regarding point of application but I could not understand what it really means
Let's suppose you have a ball and you throw it on a rigid wall now the ball comes back (neglect gravitational force). So if someone asks what is work done by the normal reaction we would say that as $W= F ... |
The permanent magnet is being moved away from the ring. How to determine the direction of the inductional current in the ring?
Here's what I've tried.
Magnetic field lines go from the North pole of the magnet to its South pole. The ring is attracted to the magnet => the ring pole near the magnet and the magnet pol... |
Imagine we have this situation:
We want to know the $\theta$ in the equilibrium. However since there is not a fixed point around which everything turn around I don't really know how to find the generalised forces to use the D'Alembert principle.
|
After watching this video, I was confused at why reducing the peak slosh force made braking easier, after all it's the same mass inside the truck, plus, shouldn't the overall force over the whole braking distance (area under curve) be the same, only the peak force being decreased?
Does this have to do with the rear tyr... |
So here is a thought, lets fix a cube of side 1cm, it contains light passing through it from all possible angles, be it stars or insect.
If we change our angle of view we can see different objects due to the infinite information passing through it in forms of photons. (By using microscope we can even extract more infor... |
In an exam, I am given a situation where a student investigates how the current varies with potential difference for two bulbs of the same type.
For the same voltage, the current of bulb A is twice the current of bulb B.
The conclusion made in the mark scheme is that since the power dissipated by bulb A is twice the po... |
In an energy band diagram the Fermi energy for both p-type and n-type are the same. Shouldn't the Fermi level be higher in the n-type because it holds the 5th electron very loosely therefore having greater energy?
|
A friend of mine unintentionally did an optics experiment. Basically, she wanted to cover her bedside lamp with a pattern of small holes, although she wanted the light projected from the bedside lamp to be homogeneous, i.e., like a normal bedside lamp. But when she did it, she realized the light from the bedside lamp's... |
If an isolator gets charged (e.g. by rubbing it to an other isolator), it can get charged. If it is negatively charged, I would expect the additional electrons to be in the conduction band, so that they can move freely through the insulator?
If this is true, why can we not just inject an electron at the one side of the... |
Griffiths says
...if the space is entirely filled with a homogeneous $^{10}$ linear dielectric: in this rather special circumstance we have
$$
\boldsymbol{\nabla} \cdot \mathbf{D}=\rho_{f} \quad \text { and } \quad \boldsymbol{\nabla}\times \mathbf{D}=0
$$ so
$D$ can be found from the free charge just as though the d... |
From the top of a cliff, a stone is thrown vertically upwards with a speed of 21.8 m / s. From the same height, a second stone is dropped 3 s later. Both stones hit the ground simultaneously. Under these conditions, considering that there is no friction with the air and that the movement is carried out in a single dime... |
One of the postulates of quantum mechanics is that for every observable $A$, there corresponds a linear Hermitian operator $\hat A$, and when we measure the observable $A$, we get an eigenvalue of $\hat A$ as the result.
To me, this result seemed to come out of nowhere. While I could understand representing an observab... |
Is there any way to find out if a magnet is a neodymium, ferrite(ceramic), samarium cobalt or alnico magnet (based on color, texture, etc.)?
|
I'm aware that refractive index usually correlates with density. I'm curious to know if there are strong counter examples to this rule.
In particular I'm interested to know if there is a pair of materials, one with greater density and lesser refractive index, the other with lesser density but greater refractive index.
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.