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10 views

How do capacitor plates maintain equal but opposite charges in a circuit?

I have a question regarding capacitors and their charge neutrality. When capacitors are used in circuits, the assumption is often made that the plates of the capacitors have equal and opposite charges....
0
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0answers
5 views

Is there a maximum limit on the distance beyond which we can't resolute an image using a reflector telescope in the visible light spectrum

Through Rayleigh's Criterion, it is implied that there is a maximum distance beyond which we cannot resolute an object. This limitation is due to the limitation in the size of the aperture of the ...
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1answer
19 views

Derivation of $\frac{d}{dt}\mathbf L = I \dot{\boldsymbol \omega} = \mathbf M - \boldsymbol \omega \times \mathbf L$

I would like to know how the above quantity is derived (Here $\mathbf{M}$ is the rate of change of angular momentum with respect to a non inertial frame).I tried looking at various sources and couldn'...
-1
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0answers
16 views

Does the potential gradually decrease as we move from higher potential level to lower potential level of acell

Does the potential gradually decrease as we move from higher potential level to lower potential level of acell through a conductor or It just remains the same throughout
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0answers
8 views

Puzzle based on a long-tail pair

I was recently given the following question as an optional extra on small signal analysis of transistor circuits which would not be covered in the tutorial. It is as follows: Under small (AC) signal ...
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0answers
8 views

What causes the charges in conductor to move towards lower potential terminal of cell

Whenever a conductor is connected to a cell,what causes the conventional positivecharges inside it to move towards the lower potential level of cell.. My question is whether the charges experience a ...
0
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2answers
18 views

What is the probability of QED interactions?

In Feynman diagrams of QED vertices of interaction are often labelled by the amplitude sqrt(alpha) where alpha is the e.m. fine structure constant. When higher order diagrams are constructed, each ...
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0answers
15 views

How does Cell mechanism transfer charges against potential difference

In case of a cell,the positive charges (conventionally)move from Higher potential to lower potential..but how actually it happens when charges reach to lower potential terminal of cell ,whether cell ...
1
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1answer
9 views

Does the number of accessible microstates decrease overall when heat is transferred?

We have two systems of ideal gas with different temperatures. $N$ & $V$ are being kept constant. The number of accessible microstates of each gas is thereby only influenced by a change in $E$. ...
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0answers
22 views

Is there only one “master” field in string theory?

Others have asked how many quantum fields there are according to the Standard model (How many quantum fields are there?). In a comment on that post, it was claimed that in string theory there is only ...
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0answers
11 views

Is it possible for $\beta$ be negative in Boltzmann probability distributions? [duplicate]

I am studying the basics of statistical mechanics and Boltzmann distribution. I tried to use the idea to find natural income distributions, through the method of maximization of probability using ...
0
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0answers
11 views

Representations of the Conformal Group in d Dimensions

In the first edition of Conformal Field Theory by P. Di Francesco, P. Mathieu and D. Sénéchal, to obtain the full generators of the conformal symmetry, they used a trick: First, study the action of ...
1
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1answer
44 views

Is $\nabla \times \mathbf{D} = \vec{0}$ necesary to apply Gauss Law in $\mathbf{D}$?

Electrostatic scenario. My professor told me that to use Gauss Law (at least in it's integral form) to find a vector field $\mathbf{D}$, $\nabla \times \mathbf{D}$ must be $\vec{0}$. When we derived ...
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0answers
18 views

Electron beam is a pure plasma?

I remember in a university experiment that we used a teltron tube that consisted of a vacuum tube (or gas tube to see the electrons) and an electron gun that emits electrons that enter a region of ...
-1
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2answers
53 views

“Micro” explanation for time dilation?

I understand the explanation, for example, about a light beam reflecting between two mirrors on the space craft. But what I am looking for is what aspect of traveling at very high velocities must slow ...
0
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1answer
14 views

Larmor equation and decelerated particles

From the Larmor equation: $P=\frac{q^2a^2}{6\pi\epsilon_0c^3}$ so an accelerated particle radiate. Is this true also for a decelerated particle?
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0answers
8 views

Inverse of Wave Reduction

Let's consider a system of three apparatuses. Sequentially these act as A device that measures momentum of an electron Parallel plates where electric field between them changes randomly. Same device ...
-2
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1answer
21 views

Any machines that use currents in nanoampere?

Milliampere and microampere is quiet common in human-made machines, are there examples of machines that use nanoampere currents?
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0answers
24 views

How is the vector potential integral derived?

I tried to find an answer to this but haven't yet. Going through Jackson's Electrodynamics, the following steps are used to determine the vector potential as the curl of $\mathbf{B}$. The context is ...
0
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0answers
11 views

Additions to the stress-energy tensor that leave equations of motion the same

In short: For a stress-energy tensor $T^{\mu\nu}$, what are possible additions that will leave the tensor equations of motion $\nabla_\nu T^{\mu\nu} = 0$ unchanged? Context: Any modification, $T^{\...
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0answers
8 views

Configuration Interaction for Hydrogen Molecule

Reading a book (do I need to cite?)on Quantum Chemistry, it introduces Configuration Interaction using excited slater-determinants in an Ansatz for a molecuar wave function. So the wave function will ...
1
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0answers
10 views

Efficient method to evaluate the Christoffel symbols and Riemann tensor in Bondi-Sachs coordinates

In General Relativity we may employ the so-called Bondi-Sachs coordinates $(u,r,x^A)$ adapted to a null foliation. The level sets of $u$ are null hypersurfaces and $(r,x^A)$ are coordinates on the ...
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0answers
6 views

What is the precise ECI frame for two-line elements?

I am trying to reproduce an SGP4 test vector (page 80 of http://www.celestrak.com/NORAD/documentation/spacetrk.pdf), at epoch + 0 (TSINCE=0 in the output table). It should be purely about geometry, no ...
1
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0answers
21 views

Gear Reduction -> Gear Multiplication. Will it work?

I've seen a few cool videos where there is series of gears such that the first gear spins extremely fast while the last gear doesn't appear to spin at all. I think it would be cool to build a machine ...
-3
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0answers
32 views

Is evolution a violation of natural law? [duplicate]

According to the laws of nature progression is always downward. One of these laws is the Second Law of Thermodynamics which says that isolated systems cannot increase in complexity. For example, a ...
2
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1answer
37 views

If the magnetic force doesn't do work then what does it?

Let's assume I have a conductive rod with mass $m$ and with steady current $I$. I can make the current flow in such a direction and magnitude that the magnetic force will make it move up, thus ...
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0answers
36 views

Why is a cell tower more dangerous than a stadium lights tower [closed]

Why a Wifi router with 100mW output power is suspected to be more dangerous (harmful for living things, perhaps has ionizing effect) than a 100W LED floodlight (assuming 50% efficiency of the LEDs ) ...
1
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3answers
26 views

is the centripetal acceleration have constant direction?

Suppose that we have a circular path which has a radius of $r$ and constant velocity $v$ that is tangent to the circle that the object moving around, I know that centripetal acceleration is expressed ...
2
votes
1answer
31 views

Does Bernoulli's equation describe why my curtains stick to the mesh?

I was sitting right in front of a big window (with a mesh) with curtains open, suddenly wind swooshes in, curtains sway forth and back. While they sway backward, they stick to the window(mesh) as if ...
0
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0answers
7 views

What is the geometry to achieve worst flow coefficient for a discharge hole in a pipe?

I was debating with a friend about discharge coefficient and how you can obtain the worst possible geometry for a flow of air in a tube, i.e.: reduce the mass flow rate as much as you can through a ...
0
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1answer
24 views

Question about a chapter in Feynman's book

I was reading six easy pieces by Feynman, and I had reached the section on the Conservation of energy This chapter was defintly one of the harder ones so far, especially considering that his ...
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0answers
12 views

Is the analytical dependence of the theoretical Higgs potential with temperature known?

At the very beginning of the unvierse, the Higgs potential had a paraboloid shape. After the electroweak Symmetry Breaking, it took the mexican hat shape. Is the analytical dependence of Higgs ...
0
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1answer
34 views

The Quantum Hall Effect

In the integral quantum Hall effect, one has that in regions where $_{Rxy}$ (the Hall resistance) is a constant, $R_{xx}$ surprisingly goes to zero. Why does that happen? Do impurities in the material ...
1
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0answers
26 views

Graph of $dQ/dt$ discontinuous

Charge is quantised then why how do we define $dQ/dt$ as current when graph of $Q$ v/s $x$ will be discontinuous and hence non-differentiable. Is it an approximation we use?
2
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2answers
40 views

Why can materials like sandpaper deform hard metals?

I don't have much of a physics background, so my assumptions might be somewhat incorrect. But I've recently seen how sanding tools can be used on materials that are powerful, such as stainless steel. ...
0
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1answer
18 views

Can bouyancy force result in action-reaction pair?

Question When a body is immersed in an liquid the liquid exerts buoyant force on it. But does the body also exert a reaction force equal to the buoyant force on liquid as per Newtons 3rd law.
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11 views

Markov Approximation and Master Equation Derivation

In deriving the master equation, I am coming across the Markov Approximation which says: Suppose environment $E$ and system $S$ interact and exchange some energy with each other. Then $E$ would ...
-3
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1answer
22 views

Current flows without any potential difference [duplicate]

why current if flowing if there is no potential difference. if no potential difference then no work is being done on charge so there should be no net displacement of charge but we know that the ...
-3
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0answers
51 views

Is evolution a violation of natural laws? [closed]

According to the laws of nature progression is always downward. One of these laws is the Second Law of Thermodynamics which says that isolated systems cannot increase in complexity. For example, a ...
0
votes
0answers
11 views

Regarding the meaning of the off-diagonal terms of the stress-energy tensor

It's often stated that the off-diagonal terms in the stress-energy tensor signify shear while the diagonal terms are normal pressure terms (you get a displacement in the direction you apply pressure). ...
0
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1answer
59 views

Quantum mechanically, is superposition a sum or a product?

This question may sound like a no-brainer, but I'm getting confused after watching this lecture (cf. the slide at minute 5:07). The context is to motivate the quantization of a field which, for the ...
0
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1answer
54 views

Question about some symbols in quantum mechanics

I'm tring to understand some symbols in physics formula for example in Ehrenfest’s theorem $$\frac{\partial}{\partial t}\langle \hat Q \rangle = \left\langle \frac{\partial \hat Q}{\partial t} \right\...
-1
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2answers
36 views

Why is the torque around axis 1 zero? [closed]

Consider a uniform cylindrical rod mounted on a horizontal frictionless axle through its center. The axle is carried on a turntable revolving with constant angular velocity Ω, with the center of ...
0
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1answer
25 views

Speed of a particle at a distance in an electric field [closed]

Four particles each of mass $m$ and charge $q$ are held at the vertices of a square of side '$a$'. They are released at $t=0$ and move under mutual repulsion. Find the speed of any particle when it's ...
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0answers
14 views

Fundamental Limits for Photon Detection

In quantum electrodynamics "photons don't have positions". The physical relevance and consequences of this fact has been discussed on this site 1. (Further relevant questions about the concept of ...
1
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0answers
36 views

Interpretation of different types of transformations on fields in the case of Poincarè group

I have problems understanding how transformations of Lorentz or Poincarè groups act on fields. We can think about two ways of transformation of a field $\phi_r(x)$: $$\phi_r(x) \rightarrow \phi^{'}_r(...
0
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2answers
15 views

How does current flow when all the electrons are already moved to neutralize the external charge given?

My textbook says the following: Suppose we put $+Q$ and $-Q$ charges at the two ends of a copper wire. The electrons will be accelerated due to an electric field towards $+Q$. They will thus ...
0
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0answers
17 views

Why is the CMB fluctuations (two-point correlation) approximately Gaussian?

I was learning about the Inflaton model and by quantizing it ,I can derive a $1/k^3$ power spectra , which is the Fourier transform of the fluctuation correlation function. But that doesn't give a ...
0
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1answer
39 views

Find minimum separation between two projectiles [closed]

Two particles $A$ and $B$ are launched simultaneously from point $P$ and $Q$ respectively as shown in figure. Find the minimum distance between particles in meters. Solution(brief outline): We will ...
1
vote
2answers
29 views

Drops and surface tension

When a drop of liquid splits into a number of drops, each drop tries to minimize its area but the overall surface area of drops increases. How does the overall surface area of the drops increase????

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