Electrodynamics without fields?
Can one describe electrodynamics without any reference to fields? I think you can. Using the Heaviside-Feynman expression for the electromagnetic field due to an arbitrarily moving charge, together...
View ArticleWhat causes gas particles to accelerate so that P = F / A
Dear Physics Forums, Pressure is force / area, and force is mass * acceleration. When you have a gas in a container, it's said to exert a pressure on its container. Therefore, the particles are...
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Confused about forces - can anyone help?
In the first diagram below, there is a horizontal board and it is attached to a vertical board via a pivot, P, but is also hooked via a nail (red), and the vertical board is resting on the ground. If I...
View Articlewhy does valence electrons not produce electric field in the space?
let X be any hypothetical isolated neutral atom and X- be the anion formed when X gain 1 electron this extra electron is in the valence energy orbit(band) and X- being charged produces electric field...
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Balancing forces on a bicycle wheel
Hi, (this is not a homework question) If I have a bicycle with COM, M (in line with the center of the wheels, C) on an incline, angle Φ, and the bicycle is NOT moving at all because the brake is on at...
View ArticleLangrangian in non-inertial frames?
I'm not entirely sure how to treat non inertial frames in the lagrangian formulation, do the normal rules still apply?
View ArticleEquation of Virtual Work VS Potential Energy
For linear elastic materials (3D General)... The virtual work equation looks exactly like the equation for potential energy except that in the potential energy equation, the internal work term has a...
View ArticleAny limitation on Ohm's Law?
I have been thinking about Ohm's Law in one particular situation. say I have a trace on top of a ground plane on a pcb. A signal is driven from point A and terminated by a load at point B. Looking at...
View ArticleDodgy step in the Far field approximation
The Fresnel diffraction integral is: [itex] A(x_0 , y_0 ) = \frac{i e^{-ikz}}{λz} \int \int dx dy A( x , y ) e^{\frac{-ik}{2z} [(x - x_0)^2 + (y - y_0)^2]} [/itex] When we want to obtain the Fraunhofer...
View ArticleWhere does the energy go if I raise and lower a block?
Okay, let's say I'm holding a wooden block. I then raise it above my head, then lower it to it's original position. Neither the kinetic or gravitational potential energy of the block has changed, so I...
View ArticleConservation of angular momentum
Hi, I am by now very used to the concept of conservation of momentum and energy, however i had never solved a problem using the conservation of angular momentum. Well, in the case where angular...
View Articleelectric flux and charge
eletric flux and charge have same units ie coloumb is it a coincidence or some similarity exists btw these two? electric flux density D= εE is used for calculating flux ψ not E .why?(read tht it is...
View ArticleCoriolis force - Question about sign
Dear all I have a question concerning the Coriolis acceleration expression. I learnt it as Ac = -2ω x v, where ω is the vector which indicates the rotation axis direction of Earth and v the velocity of...
View ArticleTotal Work out of Three Bodies (Thermodynamics)
The problem is: Having three bodies with thermal capacities (C) as sources of heat to a heat machine, what is the maximum work I can extract from this system, given that the bodies are at temperatures...
View ArticleEquation for transverse wave
What is [an] equation for a transverse wave with no boundary conditions, as a function of x and t? I want to model a fluctuation string where neither of the ends are bound.
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Causing levitating magnet rotation
I have a device like this one: http://www.youtube.com/watch?v=kA_hw_lY-OY (All of them work the same) Here's an image: I want to make it spin without touching it with hands. I tried using magnets of...
View ArticlePlotting potential of 2 bodies.
Hi everyone, Im currently following an example of this paper: http://ocw.mit.edu/courses/aeronauti...7F09_Lec18.pdf And have reached a standstill on page 5. Im trying to plot the pseudo potential of...
View Articletrajectory of objects in imperfect conditions.
I am familiar with standard distance-time models for paths of projectiles in perfect conditions, ie, where the curvature doesn't play a role, and where gravity is constant no matter the height. My...
View ArticleEntropy is a measure of energy availiable for work ????
"Entropy is a measure of energy availiable for work". Can someone explain this to me? Give some examples that show in what sense it is true. It has to come with a lot of caveats, proviso's etc. because...
View ArticleCockcroft-walton generator, How to increase voltage?
Hey guys, I have a question concerning CW generator which might be a bit stupid: How can we increase the voltage by using an AC source, capacitors and diodes ? Capacitors is used to store charge, diode...
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