0
votes
0answers
1 view

rectifiers physics fundamental of electronic devices

What value of filter capacitor is required to produce a 1% ripple factor for a full-wave rectifier having a load resistance of 1.5 k"ohms"? Assume the rectifier produces a peak output of 18 V.
0
votes
1answer
15 views

Why do planets move in fixed orbits?

Is it because the bending of space that occurs around the Sun creates a force acting on the planet which accelerates it towards the Sun (F=ma) while the planet has a tendency to move in a straight ...
0
votes
1answer
16 views

Quantization in Black Body Radiation [duplicate]

Why does energy need to be quantized to explain black body radiation? Wouldn't the approximate normal distribution of the kinetic energy of particles at a certain temperature be sufficient, ie. few ...
-2
votes
2answers
22 views

Finding the initial velocity of projectile

What is the formula for calculating initial velocity of projectile using the conservation of energy given the mass, height, angle ?
2
votes
0answers
11 views

Fluid flowing into small pores

I have some open porous foams with pore sizes ranging from 50-100nm. I want to flow water into this structure but even at 30 atmospheres it would NOT go in. I am looking for a way to calculate the ...
-3
votes
0answers
25 views

Why does this not make infinite energy?

Here's an idea I had for infinite energy: Get into a spaceship, and fly to a star or other large body and get into orbit. Then just harvest your kinetic energy somehow and keep going indefinitely. My ...
0
votes
0answers
16 views

Are Q1 and Q2 attracted or repelled to the sphere shown in the figure below?

Can you tell from the image below if Q1 and Q2 are attracted or repelled. Will Q2 only be attracted to the sphere if Q2 is enough bigger than Q1? Will the positive charge inside the shell attract ...
0
votes
0answers
12 views

How do you calculate the magnitude of the light waves emitted from an LED?

Question is in the title. My goal is to see if this is enough to make an interferometer using a surface-mount photodetector.
6
votes
1answer
57 views

What is the exact meaning of homogeneity in cosmology?

I understand that, in general, homogeneity is the physical attribute of being uniform in composition (" of the same form at every point"), but I'm slightly confused when it is used in cosmology as ...
0
votes
0answers
5 views

Finding the frequency of vibration of part of a system

The setup: 4 spheres of diameter 1 are suspended on a horizontal plane (magically). They are arranged in a square with length one. The velocity of a wave in the medium they are suspended in is equal ...
0
votes
0answers
22 views

Negative Sign in the Gravitational Potential Energy

This is the derivation of gravitational potential energy. (zero potential at infinity) $$U = -\int_\infty^r\vec{F}_\text{field}\cdot d\vec{r}$$ After the dot multiplication: $$U = -\int_\infty^r ...
0
votes
0answers
5 views

EW phase transition and baryogenesis

There are three Sakharov conditions of baryogenesis: CP symmetry violation. Baryon number conservation violation. Thermodynamical equilibrium violation. In SM the first one is satisfied by CKM ...
0
votes
1answer
17 views

Relativity and observable universe

Will cosmological horizon "expand" for an observer approaching the speed of light (at least in the direction of observer's motion) ?
0
votes
0answers
11 views

Find direction and magnitude of net electrostatic force on a point charge

Question: Find the direction and magnitude of the net electrostatic force exerted on the point charge $q_2$. Let $q = +2.4μC$ and $d = 33cm$. What I tried: I used the formula $F = kq_1q_2/d^2$ to ...
1
vote
0answers
44 views

What's the advantage of using bra-ket notation over inner-product notation? [on hold]

Both notations look pretty similar, and appear similar when undergo algebraic operations. Apart from personal taste (aesthetics) concerning commas (<,>) vs. pipes (<|>), what is (are) the ...
0
votes
1answer
14 views

derivation qm canonical ensemble

In classical mechanics the canonical ensemble can be derived from the microcanonical ensemble of two systems in weak interaction. Is a similar thing possible in quantum mechanics? Is there any good ...
1
vote
2answers
50 views

How does this youtube video demonstrate quantum entanglement? [on hold]

The following is an experiment that shows "spooky action at a distance" of quantum entanglement; that is, when we measure some properties of two entangled photons, we find that measuring property of ...
0
votes
0answers
44 views

Conservation of angular momentum - exercise

A sphere of mass $M$ is rotating with constant $w_0$ regarding the axis that intersects the north and south pole of the sphere. A bug of mass $m$ sits on the north pole and starts to walk along a ...
0
votes
0answers
48 views

What is the difference between configuration space and phase space?

What is the difference between configuration space and phase space? In particular, I notices that Lagrangians are defined over configuration space and Hamiltonians over phase space. Liouville's ...
0
votes
0answers
10 views

Ruthenium Dyes in Gratzel Cells

Can one replace the expensive 4d transition metal, Ru in Gratzel Cells by inexpensive 3d transition metals, such as Fe?
1
vote
1answer
25 views

Struggling with whether its $\pm p dV $

I am struggling to understand when calculating the work done by a gas whether it is postive or negative p. It my notes and in many other notes sometimes it is $-pdV$ and sometimes it is $pdV$. I ...
0
votes
3answers
33 views

Why do only heavy radioactive elements perform fission or fusion?

Why do only heavy radioactive elements perform fission or fusion? I mean what's so special about heavy elements which makes them ideal for nuclear fission? Also why do only neutrons show ...
0
votes
0answers
8 views

Functional form for k-logistic diffusion process

I'm trying to model a diffusion process characterized by subsequent logistic diffusion processes. To give a better idea of what I'm trying to model, you can take a look at the attached figure. In such ...
3
votes
2answers
257 views

Can I do something for being heavier to be lifted?

Playing with a friend, one started to try to lift the other, and then the other way back. We started to talk about "making some force" to be more difficult to lift - one could think about having more ...
0
votes
0answers
11 views

Chemical potentials of SM particles at high temperatures

Recently I've heard the statement that chemical potentials of SM particles on $T > 1 \text{ GeV}$ are very small, so that Gibbs potential reduces to free energy. How to prove this statement? Does ...
-2
votes
0answers
22 views

Resistors in series [on hold]

Let $P$ be the equivalent power of three resistors of powers $P1$, $P2$, and $P3$, and let $I$ be the current flowing through the circuit. We know that voltage is $V = v1 +v2 + v3$ and: $$V = PI\\ ...
-3
votes
1answer
23 views

Non zero accetion, varying speed

Can an object have non zero acceleration without having varying speed? How? Can you explain with an example please.?
4
votes
1answer
63 views

How does one express a Lagrangian and Action in the language of forms?

In Lipschitzs Classical Mechanics a Lagrangian is defined as: $L(q,q',t)$ for some trajectory $q(t)$ of a particle And the action is defined as: $S:=\int^a_b L(q,q',t) dt$ How does one ...
-2
votes
0answers
18 views

Max speed of a turning disk for an object to stay at rest

A coin is at rest relative to a disk moving with a angular speed of w: The coin weighs 0.010 kg The distance of the coin to the center of the disk is of 0.20 m The static friction is of 0.45N ...
3
votes
2answers
43 views

Why does the water bottle not rotate when it is half full?

Consider this water bottle: When it is full and thrown up in the air, it rotates at a constant velocity. When it is less than 1/8th full, the water bottle rotates even faster than when it was ...
1
vote
0answers
28 views

Can a microwave oven induce an accumulation of static charge in food?

I often "touch test" microwaved food to see if it is heated up enough to my preference. In doing so, I sometimes notice the characteristic tingle of a static discharge between the food and my finger ...
-1
votes
0answers
16 views

Finding the magnetic field [on hold]

A mechanical pendulum is made of a metal rod, one end of which is attached to a string. The mass of the rod is $m$ and the string length is $l$. The oscillation period of the thus obtained pendulum ...
-6
votes
0answers
25 views

Why there is no mention of Archimedes Principle in whole Fluid Mechanics? [on hold]

Why there is no mention of Archimedes Principle in whole Fluid Mechanics? Without Archimedes, today we can't see Boats & Submarines.
0
votes
0answers
8 views

from control torque to magnetic moment

I am designing a system which generates a magnetic field to make itself move in space (a cubesat with magnetorquers). This magnetic field is known as the magnetic control torque, i.e. it will torque ...
1
vote
3answers
18 views

What does it mean when we say that power of a bulb is 10 W? Since $V/I=$ resistance is a constant, how can power $=VI$ be a constant?

My question is simple. In Ideal situation, at constant temperature, we know that normal appliances like a filament bulb has straight Voltage vs Current graph, meaning its resistance is constant or ...
0
votes
0answers
5 views

Velocity Selective Coherent Population Trapping and recoil limit on temperature

I have read that it is possible to go under recoil temperature limit using VSCPT (Velocity Selective Coherent Population Trapping) and that this method is based on atoms trapping in quantum state in ...
0
votes
1answer
23 views

The significance of the pressure term within the momentum-energy tensor [duplicate]

EDIT: this question is based around my notion regarding the possible role of potential energy in the momentum energy tensor T$_{\mu\nu}$, The answer below resolves the question and I have deleted ...
0
votes
0answers
21 views

Need help in understanding tensorial simplification in a special case

The Lagrangian of N=2 supergravity's important terms for my purpose are (hopefully I simplified this correctly): ...
-2
votes
3answers
80 views

Do shadows have mass?

It sounds like a joke but I just want to know if shadows have mass, since shadows are formed when there is blocking of light. It forms a black pattern with no energy therefore it has no mass.
1
vote
1answer
57 views

Books on quantum mechanics with intuition [duplicate]

So, I know that there are a lot of questions about good books on quantum mechanics and I have read each one of them, and I go on and bought Griffiths' Introduction to Quantum Mechanics. But the fact ...
0
votes
0answers
14 views

Initial current, RC Circuit

The task goes like this: The voltage between the points A and B, in the circuit diagram below, is 100 V. What's the initial current through the resistor when we close the switch S? (Other components - ...
-2
votes
0answers
19 views

Finding displacement of spring [on hold]

Q) A block lies on a horizontal frictionless surface, and the spring constant is $50\,\mathrm{N/m}$. Initially, the spring is at its relaxed length and the block is stationary at position $x=0$. ...
0
votes
0answers
31 views

Molecules from atoms [migrated]

Why does two oxygen atoms combine to form a molecule and not 3 or 4?Also why does one sodium and one chlorine atom combine to form NaCl while two chlorine atoms are required to combine with one ...
0
votes
0answers
20 views

The minimum force required to lift a triangular prism

If I have an isosceles triangular prism of mass m with the angle at the top being $2\theta$ I want to work out the minimum force I would need to apply to the upper faces to lift the prism. Lets say ...
0
votes
0answers
36 views

Solving the Three-body problem numerically

I want to create a program in $Mathematica$ that solves numerically the Three-body problem by Euler-Lagrange's equations. I was searching some methods to sucessfully do it. So I found a way to solve ...
0
votes
0answers
12 views

Scattering and form factor

In Introductory Nuclear Physics by Krane (there's a PDF online), it is mentioned electron scattering on the nucleus to get a picture of the latter's shape, e.g., its radius. It is said the probability ...
0
votes
1answer
18 views

How can electric field accelerate fog dissipation?

I should emphasize that I view the problem as a 'research' rather than a 'textbook' level. However, as I am almost unfamiliar with the subject it may be that the answer is elementary and well-known. ...
0
votes
1answer
30 views

Voltage and volume, same SI symbol, how to discern between the two? [on hold]

Both are SI quantities that use the same symbol, namely $V$. It annoys me that I might be working with the wrong unit even though it's easy to see if it's voltage or volume by looking to the whole ...
0
votes
1answer
49 views

Suggestions for GR solved problems books

Study Topic: General Relativity I'm looking for a recommendation for either a dedicated problems and solved solutions book or, failing that, a textbook with a separate comprehensive solutions ...
4
votes
0answers
34 views

Why are $W$ bosons massless above electroweak scale? [duplicate]

Because of the Higgs mechanism, one must replace the Higgs field $\phi$ with $\phi_0 + \phi_1$ where $\phi_0$ is the vacuum expectation value. As far as I understand, the $\phi_0$ gives the mass term ...

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