Electromagnetic Definition and 1000 Threads

Applications: garage door openers: 40.0 , standard cordless phones: 40.0 to 50.0 , baby monitors: 49.0 , FM radio stations: 88.0 to 108 , cell phones: 800 to 900 , Global Positioning System: 1227 to 1575 , microwave ovens: 2450 , wireless Internet technology: 2.4 to 2.6 . Which of the...

Dear ForumersI am having a bit problem understanding the phase relation between current source and the generated eletromagnetic field components. Assume a very small current element( a very small current running in direction x)(essentially an electric dipole) in a non-homogenous loss periodic...

Homework Statement One of the conditions that we must obtain for us to use the lumped circuit abstraction is that the timescale of interest in analysis of the circuit must be greater than the speed of electromagnetic propagation. What was discussed in class was how much greater. The answer...

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...

Good morning, in circuit theory I know that reacting power arise from phasors and represents a power which can't be used, because not delivered to any load, but continuously flows back and forth between the load and the generator with a zero mean during one period. I can't understand very well...

I often see the EM Hamiltonian written as $$H=\frac1{2m}\left(\vec p-\frac ec\vec A\right)^2+e\phi,$$ but this confuses me because it doesn't seem to have the right units. Shouldn't it just be $$H=\frac1{2m}\left(\vec p-e\vec A\right)^2+e\phi,$$ since the vector potential has units of momentum...

Hi all, I've a few quick questions about solenoids, just want to understand things better. As I understand it, the way a solenoid works is the iron core is sucked into the middle of the coil because this is where the coil achieves the highest inductance possible. Makes sense. Incidentally...

Hello all, This is just a question i have... I need to know the frequency (in order to meter it) from an electromagnetic source, and i know that a neodymium magnet will disrupts it. so, i want to know what range the neodymium will disrupt, in order to know what device will need to meter...

Author: Bo Thide Title: Electromagnetic Field Theory Download Link: http://www.plasma.uu.se/CED/Book/ Prerequisities: Contents:

Since temperature is no more than vibrating atoms (in Feynman's words), wouldn't that induce a changing electric field, just very slow in some cases? If so, is everything that is not 0 degrees kelvin radiating some kind of EM radiation? Like an ice cube, does it radiate small amounts of radio...

Hello, I am building a generator for a project in my physics class. I have lots of magnetic wire and 6 VERY strong neodymium magnets, their area isn't overly large (I'd say about 1.5x1.5 inches). How many coils would be best for me to make for the stator? I am making a circular spinning disk...

Hi all, I have a conceptual difficulty with the idea of induction of a current in a wire due to a changing magnetic field. Initially I was very comfortable with the idea. Upon seeing the typical setup of a square wire being rotated in a region of uniform magnetic field, I was happy to accept...

If we have a static electric charge, it generates an electric field. If that static electric charge is accelerating, it generates an electromagnetic field. What about if the electric charge is moving with uniform velocity? Is the field thus generated an electic field or an electromagnetic...

Would it just be the same as with two electrons? (or any other pair of particles with the same charge) I'm kinda in two minds, I suspect that is wrong because wouldn't the fact that they attract each other (instead of repelling) means that the diagram would be drawn differently?

Hello, I need to calculate/estimate the force between a solenoid electromagnet and a piece of iron on a certain distance from the magnets airgap, preferable in a simple way under ideal conditions rather than a very exact calculation. I have found the following formula at a couple of places...

Hello everyone i bought a kit for my senior project on electromagnetic levitation. It uses an electromagnet to suspend a magnet via force of attraction. It is stable because of two hall effect sensors and voltage regulator. The kit can make the magnet move in a sinusoidal and tangential motion...

Here is a picture of a situation I thought of: The circles between the magnets indicate a wire with current flowing in the direction given. This picture is a cross section of a loop of wire, looking down. Not included in this picture is the battery and non-conductive connecting materials...

Hello, Is there any difference between 50/60 AC current and a 50/60 Hz photon stream/electromagnetic wave propagating through a medium ?? Regards, Hex

Hello, when a coil rotates in a magnetic field an AC is produced at the ends of the coil but do that electrons come from the coil wire ? If yes, shouldn't the coil run out of electrons after some time ? thank you

Consider a magnet moving towards a coil. We know that the motion of the magnet will induce a current in the coil and the direction of this induced current is to oppose the motion of the magnet. Now does the magnet experience resistance to its motion immediately as soon as it starts...

I've been wondering how does this motor work (if it is not hoax in the first place) I was thinking about Ampere's force but apparently it doesn't really have an affect here. Any ideas?

how friction is an electromagnetic force?

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...

This thread is to move this discussion away from another thread in order to talk about it in more detail, so here is a brief recapitulation of how that went to make an opening for the discussion... A photon is quanta of electromagnetic radiation, and despite the name, despite there are, I...

We know that 1)a change in current and voltage in a coil may result in induction in other stationary coil..this induction is directly related to frequency..ie The higher the frequency the more intense the induction effect. 2)we also know that there is no induction in case of DC current flow...

We can determine what kind of elements exist in different planets by observing electromagnetic waves from planets' direction, but does anyone have any suggestion on how planets generate electromagnetic waves at the first place? Does anyone have any suggestions? Thanks in advance for any...

ElectroMagnetic Wave In Liquid.. Help with Index of Refraction?? Homework Statement Consider the propagation of an electromagnetic wave in some liquid. The y-component of its electric field is given by Ey(x,t)=4.3 x104 V/m sin(5.40E-2m-1x + 6.00E+0 x106 s-1 t). How large is the index of...

I first thought that electromagnetic induction disobeyed the law of conservation of energy since there is another current created by another current by changing it (AC). but then there is Lenz law that says when you have yourself an current and also a changing magnetic flux, there will be an...

Homework Statement 1. Explain the effects To the photocurrent as the light intensity increases To the photocurrent as the frequency of the light is increased To the speed of the photoelectrons as the radiation intensity increases To the speed of the photelectrons as the radiation...

Dear friends i know that a wave is linearly polarized if its components have a phase difference of n*∏ and is circularly polarized if phase difference is n*∏/2. But what if phase difference is neither ∏ nor ∏/2? like for E= ax exp(-j(βy-∏/4)) + azexp(-j(βy-∏/2))... thanks in advance...

I've always struggled with the commonly used measures of the intensity of electromagnetic radiation and it's catching up to me lately. Suppose \bar{P}(R,\phi,\theta) is the Poynting vector of an electromagnetic field (in spherical coordinates) with norm...

Imagine a stationary charge q located on the positive y-axis at a distance r from a stationary observer at the origin. Let us assume that the distance r is large enough such that the electrostatic field due to the charge is negligible at the origin. Now let us assume that the charge q is given...

hi, I try to use the Noether theorem to determinate the angular momentum of the electromagnetic field described by the Lagrangian density L=-FαβFαβ/4 After some calculation I find a charge Jαβ that is the angular momentum tensor. So the generator of rotations are (J^{23},J^{31},J^{12}) =...

An electromagnetic plane wave has an electric field and a magnetic field. Each component contributes equally to the energy density. Mathematically it is very straight forward to show this is true. The question is, "Fundamentally, why is this true?" Again, I'm not looking for a derivation...

Hi, my question is, if there is an interpretation for electromagnetic gauge fields, whose components are imaginary. This would lead to an imaginary magnetic field... Does anything like this exist? Or is it forbidden ny some first principal arguments? Thank you in advance for every input! Melvin

Hey all, just wondering over a very naive question but I couldn't really find the answer by looking through the web. So electromagnetic waves are self sustaining and they don't lose energy while traveling through space, except if the photons they're made out of do "collide" with matter which...

Homework Statement Two coils are place on an iron heart, like in the picture. The top Coil is connected to a galvanometer, the second could be connected to a power source. Homework Equations Will an electric current flow through the top coil when: a) connecting and then...

Is there a complex field that when properly interpreted yields the four components of electromagnetic vector potential, A_0, A_1, A_2, and A_3? Somewhat along the lines of the complex field ψ yielding information about a particles energy, momentum, and position probability. Thanks for any...

Yer.. I'm lazy and tired, did not enough research and found out that the radio/electromagnetic wave makes all the electrons move back and forth when the wave oscillates between the magnetic and electric fields... so you can see how much the current oscillates etc. But... um cameras work...

Can the magnetic wave have an influence on the electric wave?

Consider the time-reversal Lorentz transformation given by the 4x4 matrix: \Lambda_T = \begin{pmatrix} -1 & 0 & 0 & 0\\ 0 &1 & 0 & 0\\ 0 & 0 & 1 & 0 \\ 0 & 0 & 0 &1 \end{pmatrix}. In my relativistic quantum mechanics lecture, we discussed how the electromagnetic 4-potential...

Is there an equation for force due to electromagnetic radiation? For example, is there a force due to orange light?

Homework Statement Here is a question which frequently occurs on on our school test: "Prove Faraday's law of electromagnetic induction on the basis of principle of conservation of energy" I do not really know how to begin.Thanks!

First Post! So I was curious about how I could relate my new found knowledge of electromagnetic inductance on guitar pickups and I came across this on the internet: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Music_p004.shtml#background Which says, "All of these...

Homework Statement In what units is energy density measured? 1. Watts 2. Watts per cubic meter 3. Newtons per meter 4. Joules per cubic meter Homework Equations E = cB (as derived by Maxwell) The Attempt at a Solution This question is so basic yet I'm confused. I thought...

At one instant, the electric and magnetic fields at one point of an electromagnetic wave are E = (210 + 320 − 40) V/m and B = B0(7.5 − 7.5 + a) μT. Find a and B0 E=cB The Attempt at a Solution So I found a using E dot product B = 0 and I got the value a=-20.625 and this is...

A non conducting ring of mass m and radius R has a charge Q uniformly distributed over its circumference. This ring is placed on a rough horizontal surface such that the plane of the ring is parallel to the surface. A vertical magnetic field B=B0t2 τ is switched on. After 2 second from switching...

When an electromagnetic wave hits a conductor the transmitted part of the wave is damped considerably. I want to know if anyone can explain physically why the field is attentuated inside the conductor - i.e. what happens. I know the basic properties of a conductor: - Electrons free to roam -...

Lets take visible light for example. The frequency/wavelength determines the amount of energy and the type of wave(micro,radio,gamma ect.) The intensity or brightness is determined by the amount of photons. So what does the amplitude determine?

Hello, I know the electromagnetic field propagates in a 3D space so if I am horizontally aligned with the field I will receive its variation but what if I'm vertically aligned ? thanks