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### I am learning electricity and magnetism remotely, what is the best tool kit in the market for a home lab to accompany this college course?

My university suspended all labs in the physics department and there is no virtual option, but for me to understand E&M I need to see some live experiments and do them myself. What lab kit on the ...
9 views

### Does electric field exist exactly at the surface ($r = a$) or slightly above the surface ($r = a+0$) in example with charged conducting sphere?

A sphere of radius $a$ is in the vacuum and and it's evenly charged with charge quantity $Q$? Does electric field exist exactly at the surface ($r = a$) or slightly above the surface ($r = a+0$) in ...
14 views

### 2D Ising model and FK-percolation

Consider the 2D Ising model on the finite lattice $\Lambda$ with $+$ boundary conditions, i.e., all spins outside of $\Lambda$ are $=+1$. Let $\mathscr{E}_\Lambda^b$ denote the edges in $\Lambda$ and ...
24 views

### Why do we consider the ground state as the lowest energy state?

According to Bohr's theory, electrons move around the atom in orbits having specific energy. When it absorbs energy, it gets excited to higher energy states. In H2 atom, ground state is -13.6 eV while ...
16 views

### What is the difference between indistinguishability that leads to Gibbs correction and indistinguishability that leads to quantum Statistics?

In Gibbs paradox, Ideal gas is considered indistinguishable, and the partition function is divided by N factorial, how does the indistinguisabilty differ from quantum statistics?
7 views

### Pressure dependence of viscosity

Does viscosity depend on pressure? If depends, is there any equation by which I can calculate viscosity at a specific pressure?
14 views

### A question about quasi-classical motion in Landau's *Quantum Mechanics (nonrelativistic theory)*

In sec.50 of this book, Landau discussed penetration through a barrier, and in the note he mentioned In a passage from right to left through the lower half-plane, the function $\psi(x)$ at first ...
25 views

### Defying gravity with vertical shaking?

I saw this video on levitating a denser liquid on less dense air by vertical shaking. But I couldn't understand some points in the video. 1 : How did the liquid levitate at 0:37 or at any moment? I ...
15 views

### How does moving your legs forward on a swing propel it forward instead of backward?

Moving your weight back is equivalent to moving the pivot forward, like having a ball on a string and moving your hand forward, then, when it moves forward, moving your hand back. What I don't ...
22 views

### A question on position and velocity vectors from a vector space perspective

In introductory physics we are taught about position and velocity vectors. Though the representation of those vectors is identical (i.e. $x\hat{x}+y\hat{y}+z\hat{z}$) they must belong to separate ...
12 views

### Total Energy of a Flowing Fluid

Does image I and image II have a different equation? or is it just PE difference?
12 views

### Is gravitational Force is damping force in vertical mass-spring system of constant k in Simple Harmonic motion

When a block of mass m is suspended by vertical spring system,it for sure perform SHM in the absence of damping force,only force which act on the system is internal which is -kx, where k is spring ...
10 views

### Collimation issue with an DIY spectrograph

I am trying to make an educational echelle spectrograph using easily available materials, basically in a cardboard box. An echelle grating (36 lines/mm) needs another prism to do a cross dispersion ...
20 views

By the way, I don't know why the following Latex syntax does not compile properly in Stackexchange. So, I type them in Overleaf, where I use \usepackage{physics} and take a photo. Let $\{ \ket{1} \ket{... 0answers 21 views ### Four momentum product [closed] Can you please help me to understand how to get$p_1 . p_2$? I could not understand what happen to$T^2$or MT, ET terms in$p_1 . p_2$? Thanks in advance. 0answers 15 views ### What happens to the information content of the universe in the deSitter phase? What happens to the information content of the universe when the accelerated expansion enters the empty deSitter phase in the distant future? 0answers 13 views ### Equivalent resistance of a circuit with backwards diode [closed] Please help find equivalent resistance of this circuit, as well as the current drawn by it. 1answer 38 views ### Why is the colour of the black texts appearing Yellowish and Purplish? I was revising some of the concepts from my old copies and I noticed something really weird (might not be weird for others). The texts with black pen when seen from behind the page had some yellowish ... 1answer 20 views ### When to use Significant Figures? When do I use significant figure rules in physics for arithmetic. I already know that I have to use it for unit conversions. Where else would I have to use it? 0answers 15 views ### (McIntyre$3.5$) Calculate state of a system that is evolving in uniform magnetic field [McIntyre Question$3.5$]: Consider a spin-1/2 particle with a magnetic moment such that $$|\psi(0)\rangle =|+\rangle_{z}$$ The system is allowed to evolve in a uniform magnetic field $$\vec B=B_0 \... 1answer 22 views ### Degrees of freedom for a bead on a parabolic wire? How many degrees of freedom does a bead on a parabolic wire have? I think it must be two degrees of freedom since the bead is constrained to move on the wire (up, down motion and left/right motion). ... 0answers 23 views ### Quantum Field Theory Identity We are asked to show that$$\not A\not B = A\cdot B - i\sigma_{\mu\nu}A^\mu B^\nu $$I know that$$\not A = A_\mu \gamma^\nu $$by definition, and:$$\sigma_{\mu \nu}=\frac{i}{2} [\gamma_\mu, \gamma_\... 1answer 28 views ### Longitudinal and transverse mass Then, it was pointed out by Thomson and Searle that this electromagnetic mass also increases with velocity. This was further elaborated by Hendrik Lorentz (1899, 1904) in the framework of Lorentz ... 0answers 9 views ### A plane has speed relative to air of 250 km/h. The displacement is 480 km (E 20 degree N). Wind is blowing at 40 km/h (E 30 degree N) [closed] A plane has speed relative to air of 250 km/h. The displacement is 480 km [E 20 degree N].Wind is blowing at 40 km/h [E 30 degree N] a) In what direction should the pilot fly the plane? b) How long ... 0answers 22 views ### Confusion about electric potential for a system of rings For a uniformly charged ring, centered on the origin of the$xy$plane, with radius$ a $and$ q< 0 $, I know that the electrical potential in any point in$z$is given by: $$V = \int_{ring} \... 1answer 16 views ### Magnetic field strength just outside of a solenoid From my understanding, the magnetic field inside a solenoid is constant, so at points C and D, the magnetic field strength is the same. Magnetic field strength outside solenoid is minimal and is ... 1answer 15 views ### Differences between the complex networks and social networks How could I state in simple terms the differences between the literature of Complex Networks (after Albert-barabasi and Watts-Strogatz - Physics Literature) and the literature of Social Networks (... 1answer 20 views ### Sig Figs when finding Slope When finding the slope of a position vs time graph, do you use sig figs? for example, if the slope is 150m [N] / 10s, would the answer be 20m[N] / s (because the least amount of significant figures in ... 0answers 19 views ### Question about delayed choice quantum eraser experiment Suppose all the entangled photons have already reached the interference screen before the entangled pairs could reach the quantum eraser, will we see interference? because we did destroy the ... 0answers 12 views ### Find the electrostatic force per unit area on a conductor shell I want to calculate the electrostatic force per unit area at r=a. Firstly we can easily calculate the electric field inside the shell for r<a: D(r)=\frac{q}{4πr^2}+\frac{ρ_0r}{3}. Afterwards ... 0answers 20 views ### Free particle on sphere The Lagrangian of free particle on a unit sphere is L=\frac{1}{2}m \sum_{I=1}^3 \dot{x}_I^2 + \lambda (\sum_{I=1}^3x_I^2 - 1), where \lambda is the Lagrangian multiplier. The equations of ... 0answers 46 views ### General relativity tattoo [closed] I apologise for asking this question on here but I feel it was the best place. I am huge fan of Einstein and want to get a Tattoo of one his general or special relativity equations put on my back. E=... 2answers 22 views ### Why is the magnetic field produced in an electric wire circular? If electric current is the movement of electrons, to what do the electrons in a wire get attracted to get a circular magnetic field? 0answers 5 views ### Measuring momentum in a 2 height well In a 2 height finite square well we know that qualitatively the position wavefunction will have a lower amplitude in the side of the well with a smaller potential energy (since it will be travelling ... 0answers 18 views ### Wrong application of optical theorem I am trying to use optical theorem* ( given in box 24.2 in Quantum Field Theory and the Standard Model, M. Schwartz ). I am trying to calculate the imaginary part of this diagram for the scalar field: ... 1answer 21 views ### Do neutron star merger studies probe beyond vacuum GR? When mergers involving neutron stars and / or black holes are simulated (e.g. when predicting gravitational wave signatures for these mergers), obviously complicated numerical relativity calculations ... 1answer 28 views ### Expressing a quantum mechanical state as a linear combination of the basis kets of an observable I have a question. Suppose we have a quantum mechanical system, of which we can measure 3 different observables. Each of the observables has an eigenvector spectrum and we can express a state as a ... 3answers 13 views ### Expression for total potential energy in coupled systems I was reading through applications of Lagrangian mechanics and the case of coupled oscillators. The example provided is the famous two pendula length l mass m hanging from the ceiling connected by ... 1answer 31 views ### Interpreting spherical harmonics angular momentum eigenstates I'm trying to get some intuition behind the spherical harmonics being the angular momentum eigenstates in quantum mechanics. Firstly, am I correct in saying that we can imagine the angular momentum (|... 5answers 165 views ### An unintuitive situation related to work and energy Consider an object which has been given a speed v on a rough horizontal surface. As time passes, the object covers a distance l until it stops because of friction. Now, Initial kinetic energy = \... 0answers 16 views ### Thermodynamics - Temperature Increase Velocity I came across a thermodynamics problem that I don't know how to solve. Here's what I tried to do: Problem: A cylinder filled with 1.7\space mol of an ideal gas has an initial volume Vi = 3.1*10^-3\... 1answer 22 views ### Relation between time-derivatives observed from fixed and rotating frames I will begin by stating the question and then I will explain my doubt. The relation between time-derivatives of a vector \vec{u} observed from fixed and rotating frames (with a common origin) is$$ \... 1answer 22 views ### Question concerning phase curves and Lissajous figures I want to draw the "orbits" of a spherical pendulum under small oscillations. In this case its equations are given by$\ddot{x}_{1}=-x_{1}$and$\ddot{x}_{2}=-x_{2}$. Of course the potential ... 1answer 42 views ### How would a light bulb filled with$H_2$gas behave? I am modifying light bulbs trying to use unique bottles and jars for the envelope. I was thinking I could prevent the filament from oxidizing by removing all$O_2$before sealing it, and an easy way ... 3answers 46 views ### Can you explain the meaning of buoyancy, written here? I got this Archimedes' principles from a website named smithplanets.com Can you explain why we cut the volume of water equivalent to the weight of an object when the object is floating in the water ... 0answers 13 views ### How do you articulate a vector for a waterfall falling towards the center of the earth? I'm trying to envision and think of a vector that represents a waterfall falling towards the center of a sphere (earth) that's scaling down in size towards zero as it approaches the center, as such ... 0answers 15 views ### Could antimatter have disapeared from the universe simmilarly as observed matter from collisions of black holes? As matter inside a neutron star or black hole can vanish through collisions could be possible that antimatter did so more than matter in the very beginning of the universe through a high energetic ... 3answers 32 views ### Expressing a wave on a string using fourier series Where does time function of wave on string go when expressed in the Fourier series? A Standing wave on string of length$L,$fixed at its ends$x=0$and$x=L$is:$\quad y(x, t)=A \sin (k x) \cos \...
The second Newton's law of motion is : $\vec{a} = \frac{\vec{F}net}{m}$ I wanted to ask what was the need to define first law when we can easily derive from second law that when $\vec{F}net=0$ then \${\...