Fields Definition and 1000 Threads

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 with the Lorentz force law, one can write down an expression for the electromagnetic force...

Are SM particles expected to really be i) simple excitations of their associated fields, ii) particulate matter which happens to be very conveniently (and precisely) modeled as excitations of such fields or iii) we can't judge one way or the other in the present state of our knowledge? If they...

Homework Statement Consider two infinitely long cylinders with radius a and b and currents: J = (Jo r)/a for r less than a -Jo for a less than r less than b Find the magnetic field in 1) r less than a 2) a less than r less than b 3) r greater than bHomework Equations The...

Has anyone come across an example where electromagnetic fields have been applied during crystallization processes. For example to modify crystal properties like magnetization or to change the polymorphism. In principle the use of electric / magnetic fields should change the formation of a...

If we set up an experiment in a chamber with distinct perpendicular oscillating i) electric and ii) magnetic fields, cycling at a frequency representative of visible light, will the chamber suddenly light up? If not, why?IH

I find it difficult to visualise how the magnetic field generated by a coil can be the same as the field of a permanent magnet. Are the magnetic fields the same or is it just that the effects are the same in that they both attract iron or magnets in the same fashion? Visualising the field...

Hi, I have a doubt in plotting the vector field. In the post https://www.physicsforums.com/showthread.php?t=155579 it is mentioned that a vector field could be plotted for F (x,y) by, marking the (x,y) as the tail and F(x,y) as the head portion. If so, then consider the function...

Please take a look at my program. Please help. I want to allocate memory dynamically for one field in structure. I tried to write the code but it has error. I posting a paint document for you to see. Help me please. Please tell me why is my code not working properly and what needs to be done...

I was trying to think of more impossible electric fields than my book has. I understand it is anything that breaks the rule that the path integral is zero. One example is a circular field. I was trying to picture some more complicated 3d examples. Are all magnetic fields an impossible...

Just wondering if this statement is true, GMm/R^2=v^2/R

1) Show that (R,*,+) is a ring, where (x*y)=x+y+2 and (x+y)=2xy+4x+4y+6. Find the set of unit elements for the second operation. I understand that the Ring Axioms is 1. (R,+) is an albein group. 2. Multiplication is associative and 3. Multiplication distributes. I just don't understand how to...

I guess I have no problem with time dilation for stuff moving at less than c, but the step from less than to to c, is confusing me.

Homework Statement An atom H has a charge +q (=proton) and -q(=electron). q = 1,6.10^-19. The electron is circeling around the proton at r distance r = 0,53.10^-10m. What is the force as a result of the electrostatic interaction between the proton and electron Homework Equations...

Question: Which vector field is conservative? I added two pictures of the vector fields in the paint document. So far the only things I know about conservative vector fields are.. 1. Net change is 0 for a closed path 2.there is some function f such that F = ∇f (F being the conserv...

En and Ec are the non-conservative and conservative electric field respectively. I've quoted this from the textbook I'm using (University Physics by Young and Freedman 12th edition). Now, it seems to me that the author just invoked the assumption that the inductor have negligible resistance...

The diagrams aren't coming through on my system, but the text is readable: http://books.google.com/books?id=hlRhwGK40fgC&pg=SA13-PA6&lpg=SA13-PA6&#v=onepage&q&f=false First off, I'm pretty sure he re-uses ##\rho_\omicron## to mean different things at different points in the discussion...

I was reading the Wikipedia page on "Mass in Special Relativity" (http://en.wikipedia.org/wiki/Mass_in_special_relativity) and I came across two equations: M = m/sqrt(1-v2/c2) and p = mv/sqrt(1-v2/c2) along with the following quote: Einstein's comment seems to suggest that the...

Hello! I am a bit confused about how I can use covector fields on a differentiable manifold. John M. Lee writes that they can be integrated in a coordinate independent way so I thought that the covector fields could give me a coordinate independent way of calculating distance over a manifold...

Homework Statement I need to prove that in any field : (a+b)^2=a^2+2ab+b^2 Homework Equations The Attempt at a Solution i don't know how to start the proof ... I know all the attributes of fields but i got stuck

I know that physically, they describe relationships whereby, for instance a vector field, for each point in three dimensional space (a "vector"), we have a "vector" which has a direction or magnitude. Now I once asked what the difference between a vector field and a vector function is and the...

If my question is lacking something in terms of its validity, please let me know (I am not too seasoned in electric fields) :) Here is the source of my question: http://phys.org/news198350025.html Ok... The brain produces it own electric field, by firing neurons and the chemicals that produce...

Hi, I've been trying to understand electricity... and series of questions came into my mind.. 1. I know if i move a conductor in an external magnetic field, it induces EMF, but I don't really understand INDEPTH how CHANGE in MFlux induces EMF? I think something to do with EF and MF... 2...

I am new to web design so forgive me if I come off as ignorant. Would some one direct me to a page or give me information on how to make my submit form fields required? Here is my current code: <form name="contact" action="process.php" method="post"> <label>Name</label><br /> <input...

Just posting to ask if anyone has any tips to give for a student in a Junior level Electromagnetic fields class. We usually get about 10-20 problems/week and I manage to only get 6-7 of them done every time. Also, though I generally do well with it, I'm struggling to find the energy to read...

Homework Statement What will be the net magnetic field at a point, if two mutually perpendicular magnetic forces are acting on it? Homework Equations The Attempt at a Solution

What kind of mathematical disciplines/fields take part in what's called "applied mathematics"? As far as I know, it's Differential Equations, Calculus, Statistics and Linear Algebra. What other fields are there? I'm sure there are some others.

My teacher's notes don't explain this. What are free and bound charges, and why are the H and D field defined like they are?

Recently a device invisible to a static magnetic field was described. The device features a cylinder with two concentric layers. While the inner layer consists of a superconducting material that repels magnetic fields, the outer layer is a ferromagnetic material that attracts them. Placed in a...

Let's say I get my undergrad degree in EE, but then decide to go to a different major for graduate school (i.e. PhD). Which of the following would it be feasible (or even possible) for me to switch to: - Economics - Computer science (theoretical) - Computer science (applied) - Applied and...

I want to know what exactly is magnetic and electric field fringing and what is the cause of it?

Image of the problem: It should be very straightforward: derivate p twice and insert it into the equation. I can do all that, but what is the R̅ vector supposed to be? I've read the literature, but it uses a different formula (that I'm not allowed to have with me to the exam) and it never...

I know that energy density of Electric and Magnetic Fields are (ε/2)*E2 and [1/(2μ)]B2 respectively. But I can't understand how we get those expressions. Would be really happy if you could clear my problem. Thanks a lot

Homework Statement The figure shows a zero-resistance rod sliding to the right on two zero-resistance rails separated by the distance L = 0.53 m. The rails are connected by a 10.9-Ω resistor, and the entire system is in a uniform magnetic field with a magnitude of 0.750 T. (a) Find...

This has been bothering me for a while. Consider a varying magnetic flux through a closed loop. Faraday’s law says the integral of E around the loop is V. This seems to be OK if the loop itself is split and joined with some resistance and with a voltmeter we measure across the resistor. However...

I want to prove that: Ker(T*)=[Im(T)]^\bot Everything is in finite dimensions. What I'm trying: Let v be some vector in ImT, so there is v' so that Tv'=v. Let u be some vector in KerT*, so T*u=0. So now: <u,v>=<u,Tv'>=<T*u,v'>=0 so every vector in ImT is perpendicular to every vector...

In a capacitor, specifically a parallel plate capacitor, ideally we have that capacitance is a function of permittivity, separation, and plate area. Does permeability play any role? Is all the energy stored in the electric field? Please consider this in a charge static state and also when...

I'm having trouble understanding the exponential map for nonlinear vector fields. If dσ/dt=X(σ) for vector field X, then how does one interpret the solution: σ(t)=exp[tX]σ(0) ? If X is nonlinear, then X is not a matrix, so this expression wouldn't make sense. If X is a...

Why do magnetic fields only apply force to charges/currents that are perpendicular to the field? Does it have something to do with the orientation of the field created by the moving charge in relation to the field it is in?

How can I prove that the set of all planar vector fields forms a vector space? Thanks for any input!

Hello! Im trying to read some mathematical physics and have problems with the understanding of vector fields. Th questions are regarding the explanations in the book "Geometrical methods of mathematical physics".. The author, Bernard Schutz, writes: "Given a coordinate system x^i, it is often...

Homework Statement Point charge 2.5 microC is located at x = 0, y = 0.30 m, point charge -2.5 microC is located at x = 0 y = -0.30 m. What are (a)the magnitude and (b)direction of the total electric force that these charges exert on a third point charge Q = 4.5 microC at x = 0.40 m, y = 0...

In the light that QED suggests the speed of interaction is infinite, are there any experiments which makes it clear that mediating fields are retarded in classical electrodynamics ? Whereas, on the theoretical grounds the causality requires time assymetric interaction, but do we have any...

Hello, Okay so I got a BS in physics and was so eager to work and get financially stable that I jumped into the IT world. Job outlook is pretty good. My pay has been steadily increasing and after only about 3 years of being in the field, I'm in the low 60k range. This was also due to a...

Just like calculus (single as well as multi-variable) and linear algebra are not only useful but really similar to classical mechanics. What are the branches of mathematics that I need to know in order to have that same feeling of deja-vu when studying electricity/magnetism and waves/optics? I...

If the Lagrangian is Hermitian, then fields and their complex conjugates are not independent. That is, you can solve the EOM for one field, and if you take the complex conjugate of that field, then that's how the complex conjugate field evolves: you don't have to solve the Euler-Lagrange...

what fields of math progress the most "continuously"? i have a physics BS, and have left acamedia to work. but i have an interest in going back some day and doing research, probably in math. i do some amateur math tinkering on my own, but i try hard to keep it valid and to avoid straying into...

Which is the engineering field more close to physics ? I heard about engineering physics... And even about photonics engineering, are experts in these fields to be considered even physicists ?

In some texts the author tries to interpret operations like Curl. Some say the curl of a vector field shows the amount of rotation of the vector field But some of them say,if you put a wheel in a fluid velocity field which is like the vector field at hand,if it can rotate the wheel,then it has...

Homework Statement What is the electric field in the middle of the square in magnitude and direction? four charges are arranged at the outer corners of the square in order from left to right , then top top to bottom respectively +q,-2q,-q,+2q.Homework Equations The Attempt at a Solution...

Homework Statement We have an uniformly charged disk with total charge q, which is rotating around its axis with constant angular velocity w. Calculate electric and magnetic field in the axis and in the rotation plane. Calculate the radiated power in one cicle. Homework Equations...