Fields Definition and 1000 Threads

Homework Statement A parallel plate has p.d. V with one end 0V and the other +V. B-field of strength B has direction along plates. An electron is released from rest at 0V plate. Show that if V is less than e(DB)2/(2m) the electron will not reach the other plate. Homework Equations...

Homework Statement I am going through the example problems in the book and it shows me how to find the electric field of a line of charge, which is this http://imageshack.us/a/img24/8932/img0303fq.jpg I get to this part where they change ΔQ to (Q/L)ΔY...

With my term-end examinations fast-approaching, I sat down to revise my entire senior year physics syllabus. As I was reading through electromagnetic induction, I found myself in the same state of utter confusion that I found myself in when I first studied about Lenz's Law and Eddy Currents. But...

I don;t really know how should I "tackle" this problem. The only thing I got is the answer for a) i) 1.9 * 10^11 J. It's a problem from IB Oxford Study Guide. http://img59.imageshack.us/img59/4986/fiz6.jpg I would be very grateful if You could help :) Thanks!

Homework Statement Prove Z[x]/pZ[x] is an integral domain where p is a prime natural number. Homework Equations I've seen in notes that this quotient ring can be isomorphic to (z/p)[x] and this is an integral domain but I don't know how to prove there is an isomorphism between them and...

One component of a magnetic field has a magnitude of 0.0266 T and points along the +x axis, while the other component has a magnitude of 0.0648 T and points along the -y axis. A particle carrying a charge of +2.96 × 10-5 C is moving along the +z axis at a speed of 4.71 × 103 m/s. (a) Find the...

Homework Statement An example problem I am reading is about the electric field of a uniform ring of charge. I attached the diagram provided in the problem. What confuses me is that the electric field lines in the y-direction cancel out. Wouldn't the fields have to cross, if they were to...

Hey yall. This is a question from my homework but it's so basic that it's just to help with the concept for me. So the question is this: A small object A, electrically charged, creates an electric field. At a point P located 0.250 directly north of A, the field has a value of 40.0 directed to...

Imagine nine vertical and parallel lines drawn side by side. They represent infinite planes of uniform voltage. The first line has 0 V. The 2nd line has 1 V. The 3rd has 2 V and so on, with the 9th line having 8 V. The distance between each line is 1 cm, which is 0.01 meter. There is an...

Homework Statement 1st Problem (a) Consider the electric potential V = C . r, where C is a constant vector. Find the electric field E(r). (b) For a given uniform electric field E = E(0)z^, using part (a) find the electric potential for this electric field...

Homework Statement A small conducting sphere of mass 5.0x10^-3 kg attached to a string of length 20 cm, is at rest in a uniform electric field E. There is a charge of -5.0x10^-6 coulomb on the sphere. The string makes an angle of 30° with the vertical. Calculate the tension in the string...

Homework Statement one capacitor is charged until its stored energy is 4.0 J, the charging battery then being removed. a second uncharged capacitor is then connected to it in parallel. if the charge distributes equally what is now the total energy stored in the electric fields? where the...

Homework Statement The Lagrange method does work for some velocity dependent Lagrangian. A very important case is a charged particle moving in a magnetic field. The magnetic field can be represented as a "curl" of a vector potential ∇B = ∇xA . A uniform magnetic field B0 corresponds to a vector...

Hello, I have a few questions (with regards to conducting hollow spheres) . 1: What is the difference between a charge in the sphere and an excess charge coming out of the sphere or the charge resting on the outside of a sphere? 2: Image a conducting sphere that has a shell of a small...

Hi I am working on a optimization problem involving vector fields. In order to define a objective function I need a measure (scalar quantity) of some properties of the vector field. The vector field comes from a finite element analysis, that is the vector field is calculated on a discretized...

Can anyone tell me why it is necessary to express a field as annhilation and creation operators? I just don't see why we need a field to explain the creation of particles in relativity, after all two colliding particles with enough energy produce some more.

Although I retired from active physics research almost 2 decades ago, there's a question that has annoyed/intrigued me for almost 40 years... In Classical Field Theory, matter has 2 intrinsic properties, namely mass and charge. Given Newton's 2nd Postulate, {\bf F}_{net} = m {\bf a}, I've...

Hi, A current carrying wire creates a magnetic field around it, as shown here: http://courses.ae.utexas.edu/ase463q/design_pages/fall02/wavelet/3_sour8.gif As far as I am aware this usually doesn’t cause a power loss. Even if there is a flux on a nearby conductor there will be no power loss...

Homework Statement Let f(x) = x6 + x3 + 1 in Z_2[x]. Show that f(x) is irreducible. Let E = Z_2[x]/(f(x)), and let αdenote the image of x in the quotient field. Show that E* = <α>. Homework Equations I have solved the first part, but what does E* mean? I have seen the asterix in...

Homework Statement Four charged particles are at the corners of a square of side a as shown in the figure below. (Let A = 5, B = 2, and C = 7.) Homework Equations The Attempt at a Solution Well, I first found the electric due to each particle individually...

Homework Statement In the figure below, determine the point (other than infinity) at which the electric field is zero. (Let q1 = -2.45 µC and q2 = 6.50 µC.) Homework Equations The Attempt at a Solution Here is a little commentary my author gives on this problem: Each...

Homework Statement An isotropic quasimonochromatic point source radiates at a rate of 100 W. What is the flux density at a distance of 1 m? What are the amplitudes of the E- and B- fields at that point? Homework Equations I think (but not at all sure) that the equation for flux density...

Gauss equations state that the flux of a gaussian surface is equal to the sum of all the electric field times the surface area. Although he stated this in theory, how was he able to prove it possible. What measuring device do people use to prove that this theory is correct?

Homework Statement see attachment for question wording. a) find acceleration b) find horizontal displacement c) find final velocity vx=4.0*10^6m/s ε=4.0*10^2 N/C Δdy=0.02m mass of electron = me = 9.11*10^-31kg charge of electron = qe = -1.6*10^-19 C Homework Equations suvat...

Suppose we are far from a 1000 watt source of constant radio frequency electric dipole radiation, say R/λ > 1000. Suppose this antenna is in outer space so there is no matter to make things more complicated. Stop time. Does there exist some localized (say 90 percent of the field energy in...

Homework Statement I have a coaxial cable with current density Jo in the center, with radius a, going in -z_hat direction. This generates a magnetic field. The outside of the cable, radius c, also carries a current density Jout going in the +z_hat direction. This generates its own magnetic...

Author: Steven Weinberg Title: The Quantum Theory of Fields Amazon Link: https://www.amazon.com/dp/052167056X/?tag=pfamazon01-20 Prerequisities: Contents:

Homework Statement How do you find the electric fields of regions between parallel infinite sheets of charge? The set up: 3 parallel infinite sheets of charge a,b,c from left to right. Region 1 is to the left sheet a. Region 2 is between sheets a and b. Region 3 is between sheets b and c...

Hello, this is my first post here, so hopefully I do this in the right way... Homework Statement A hollow spherical conductor carries a net charge of 21.5 μC. The radius of the inner hollow is 5.2 cm and thee full radius of the sphere is 7.8 cm. At the center of the sphere, in the...

Homework Statement Let F be an infinite field (that is, a field with an infinite number of elements) and let V be a nontrivial vector space over F. Prove that V contains infinitely many vectors. Homework Equations The axioms for fields and vector spaces. The Attempt at a Solution...

Coulomb's Law F = kqq/r^2 Why does the intensity of a uniform electric field not get weaker in the middle? I would understand this if the intensity over distance was a linear function, but it isn't. The force near one of the plates would approach infinity, because r^2 is so small... but in...

Homework Statement Having issues determining what I am doing wrong, so perhaps one of you can pin point it. I have the solution, and I am extremely close to the same result, however, I am nonetheless wrong. Find the conservative vector fields potential. \vec{F}(x, y, z)=[(2xy-z^2)...

In the Standard Model of particle physics are we to think of the electron(positron) field and the photon field as separate fields? Is it possible to think of the electron(positron) field and the photon field as just different "modes of vibration" of some more basic field? Can this line of...

Suppose I want to try and guess the fields of a short laser pulse. We know that fields that satisfy Maxwell's equations minimize the action E^2 - B^2 (say far from charge and current)? For a plane wave E^2 - B^2 = 0? Will a general solution of maxwell's equations satisfy E^2 - B^2 = 0...

Scientists can produce laser pulses of order one wavelength in "length" see, http://www.bbc.co.uk/news/science-environment-19489384 Do Maxwell's equations admit solutions of such short pulses? Can one approximate such a solution by multiplying a plane electromagnetic wave by the...

Hi all! I want to ask about vector fields. So if I had any kind of field for example \bar{F}(x,y) = (0,x) which represents a river or somthing similar and I put into the river a particle, or point-like body how can I get the path, or curve (flwo line?) from the vector field? I mean that path...

Can the products of high-energy particle collisions include the creation of electromagnetic/strong/weak/gravitational fields (whether transient or not) in parallel with or in lieu of other new particles? IH

I still have a long time to decide, but I am interested in the fields of particle physics, astrophysics, and cosmology. Here are my questions about them: 1. What field has the best outlook for the future? 2. Is there a degree that provides flexiblitiy in the choice? 3.What fields have the most...

Problem: Let f be monic irreducible polynomial over a field F, k be monic irreducible polynomial over a field K, deg f = deg k. Let u be common root of f and k. Prove (or disprove by counterexample), that f=k over field (F intersection K), i.e. polynomials f and k are identical. Proof would be...

Homework Statement Given some ElGamal private key, and an encrypted message, decrypt it. Homework Equations Public key (F_q, g, b) Private key a such that b=g^a Message m encrypted so that r=g^k, t=mb^k Decrypt: tr^-a = m The Attempt at a Solution My problem is finding r^-a...

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