Electromagnetic Definition and 1000 Threads

Hey guys, I am just a simple high school student in a one-year physics course who wants to improve his ability in applied science and using physics to create new things (my dream is to be an inventor) I always had this idea of a Maglev (electromagnetic) hover car where it uses the messier...

does every electromagnetic radiation consist of photon?

Hi, I got a C+ in my EM theory (3rd year with Griffiths book) course. I have A+'s in everything else this semester, though (including quantum mechanics II). Is this something that would hurt my grad school chances severely? My GPA is 3.48 and my physics major GPA is 3.6, for reference...

Imagine a blob of continuous charge in vacuum, the fluid elements will exert a force on each other and thus radiate away energy to infinity and thus be forever lost, does this mean that charged continuums will always lose all of its energy?

I was reading about how a plane mirror reflects light and would like confirmation I have the right theory. It says that the metal coating of a mirror is a conductor in electrostatic equilibrium which means the electric field is zero. As the electromagnetic wave hits the mirror the electrons...

In Griffiths book, "Introduction to Electrodynamics" example 8.4 he calculates the angular momentum density for a set up that is a version of Feynman disk paradox. His answer for the angular momentum points in the z direction. But if we you assume that the r vector has component in the s...

What law is being obeyed by emr traveling out from a source eg a magnetic field does not get emitted from a magnet, why does a magnetic field get emitted (eg travel outwards at speed of light) from the alternating magnetic field present in a light bulb for example? I would appreciate any help...

Hi All, Just wanted to know, is there any experimental or observational evidence today, that electromagnetic fields can cause spacetime curvature? Either direct or indirect?

Greetings everyone, I need information about how semiconductor interacts with electromagnetic radiation, the absorption, scattering, transmission and reflection properties of semiconductors. I also need to associate this information with free charges or bound charges. I would be grateful for...

Hi guys, first time poster. My question is; How would a constant damping provided by an electromagnet affect the damping ratio (and logarithmic decrement) amplitude? And how would increasing the current through the electromagnet affect the damping? So far I've found Biot-Savart's Law which...

hi pf, i have been trying to understand since last few weeks how electromagnetic waves, say light travels? Not the way transverse waves do. It must require a medium. Then in vacuum how light travels? you may answer that with oscillating electric fields and magnetic fields at perpendicular to...

Homework Statement Hey all, I am working through a derivation that my professor gave me to do and I am having trouble understanding one of the formulas that he gave me, namely: "EM waves can be described as: E(x, t) = Eosin(2πx/λ)*sin(2πc/λ)" The the Eo*sin(2πx/λ) term makes sense to...

Homework Statement I'm currently trying to understand linear and circular polarization of electromagnetic plane waves. Let's say I have an electric field given by \vec{E}=Acos(kx-\omega t)\hat{x}+Bcos(kx-\omega t - \gamma)\hat{y} A is given and nonzero. I want to find what values of...

Dear all, I am a newbie in electromagnetic wave. Can you educate me, what will happen when an electromagnetic wave is blocked by a piece of flat metal placed in front of it? My intention is to build a thermal chuck using peltier for to measure femto amps from my device. I am worried if...

What is the quantum of an electromagnetic wave? Quantum of light is photon. What is the quantum of a gamma ray or an X-ray?

hi there, In this wikipedia article https://en.wikipedia.org/wiki/Electromagnetic_tensor we have the following invariant : FαβFμη [SIZE="3"]εαβμη = 8 E*B However the determinant is the square of this quantity divided by 8, i.e. ( E*B )2 . Now from the definition of the determinant...

Do electromagnetic waves expand as they travel across the cosmos? e.g. Do the wavelengths of emitted light, from distant galaxies, have longer wavelengths when they reach Earth than they did when they were emitted?

Homework Statement A plane monochromatic electromagnetic wave (polarized in x-direction and propagating in the z direction) is scattered by a free electron initially at rest. Homework Equations \vec{E}=E_0 \exp(i(kz-wt)) \hat{x} \vec{B}=\frac{E_0}{c} \exp(i(kz-wt)) \hat{y} The...

Hi here, I am trying to make an efficient ribbon microphone motor. My target is to get a highest possible output voltage so it can be plugged into a regular mic pre-amp. It should have possibly flat output on frequences 20Hz to 20KHz. I know that electric output depends on magnetic field...

I mean, what all can you modify in an electromagnetic wave? Wavelength and amplitude right? So, for example, why does my garage opener open my garage door and not my neighbor's? Does every single wireless device have its own specified wavelength that is just fractions of meter off from others?

Homework Statement A circular coil of radius r carries a current I. A magnetic induction B acts at right angles to a diameter of the coil. Show that the current experiences a torque T about the diameter given by T=Iπr^{2}Bsinω, where ω is the angle between the normal to the plane of the coil...

So I've seen this equation used to calculate the energy associated with an electromagnetic wave: E=hf E is energy, h is a constant, and f is frequency. Therefore, the energy is related to frequency alone. However, why wouldn't the amplitude of that wave have an effect on the energy? I...

We know that electromagnetic current can be written as j^{\mu}_{em} = \frac{1}{6} \bar{Q} \gamma^\mu Q + \bar{Q} \gamma^\mu \frac{\tau^3}{2} Q where Q = \begin{pmatrix} u \\ d \end{pmatrix} . We say this induces a transition with |\Delta I|=1, \Delta I_z =0 . What should we understand under...

I pay for chegg to help me with physics but sometimes I'm not quite sure if the site is right. Could you please tell me if I am doing the below problem correctly? My way is different than Chegg's so I would just like to make sure I am not wrong because I am getting different answer than that...

From what I've learned in physics, electrons falling from higher energy levels to a lower energy level emits an photon equal to that of the difference in energy between the two levels. Each atom has a set number of energy levels for the electrons, and thus each element can only emit a set number...

Author: Roger Harrington Title: Time-Harmonic Electromagnetic Fields (IEEE Press Series on Electromagnetic Wave Theory) Amazon Link: https://www.amazon.com/dp/047120806X/?tag=pfamazon01-20 Prerequisities: Undergraduate degree in Electrical Engineering or Physics, with appropriate...

So I am in the IB, and I have to do an extended essay. I'm doing it in physics, and I'm looking at the topic "What materials offer the best shielding against an electromagnetic pulse (EMP)?" I was thinking of measuring the electromagnetic pulse using an oscilloscope. The reason I want to...

iTunes University layman looking for answers and willing to do the work – just need some direction. I now understand electromagnetic waves can be created when molecules vibrate – which they all do. I understand the frequency of the light correlates to the frequency of the molecular vibration –...

How can discreet quanta of photon energy make up a continuous electromagnetic spectrum, whose wavelengths are any arbitrary value? Is there overlap of quanta, temperature dependency, or so many finely divided energy levels that the spectrum just appears continuous? Electron energies are...

As a part of a school project I am required to build an electromagnetic tether robot. The robot needs to stay a constant distance from an electromagnetic beacon. As well as keeping a constant distance the transmitter can change the desired distance. (eg. move closer/move farther commands). The...

Hey! How to transform the equation \bigtriangleup\vec E=\operatorname{div}(\operatorname{grad}(\vec E))=\epsilon_0\cdot\mu_0\cdot\frac{\partial^2\vec E}{\partial t^2} in Einstein Notation? Thank you all for your help!

Hello! In an electro-magnetic context, the power that an electric source of field delivers to the field itself may be written as p_S = - \mathbf{E} \cdot \mathbf{J} where \mathbf{E} is the electric field produced by the source and \mathbf{J} is the corrent flowing on the source, forced by...

I have indirectly sought the answer to this for some time (since I studied an introductory course in optics 'long' ago), but nobody has been able to give a satisfactory answer, and I have not been able to find the exact answer on the Internet either. My question is about optics, and more...

Hi all, I was going through the derivation for the electromagnetic field of point charges by Griffith(Introduction to electrodynamics page 437). I'm missing minus sign somewhere: The book says that:\nabla(\vec{n}\cdot\vec{v})=\vec{a}(\vec{n}\cdot \nabla...

Gamma ray can use to kill tumour because of higher frequency and therefore higher energy. The energy here is the number of time of the wave hit on the tumor or the amplitude of wave ? Thank you.

Homework Statement Derive the continuity equation for a charged particle in an electromagnetic field Homework Equations The time-dependent Schrodinger equation and its complex conjugate are i\hbar\frac{\partial \psi}{\partial t}=\frac{1}{2m}(-i\hbar \vec{\nabla} - \frac{e}{c}...

What is the relationship between photon and electromagnetic wave? I am trying to understand light, it is so weird. Light is not an electromagnetic wave, since it has different speed in different mediums. Light does not have mass (the mass that can be derived from the energy is not a real mass)...

Can I assume that anything with high enough speed will generate electromagnetic wave? Photons are not charged. But maybe because they move fast enough, they generate vortex electric field, since this field is changing, then you have a corresponding magnetic field with it, so you have an...

As we know EM waves have a wave length. Well, how do you measure them? I have the feeling there is a path from point A to point B and that path goes up and down at a regular rate and all photons travel along that wave-path and that they are no where else between A and B but on that path. But...

EDIT! Hmmm, sorry. What is the difference between the origin of the emf in a small current loop when; a) a magnet is stationary & the coil moves, b) the coil is stationary & the magnet moves This was the original message, now realized to be incorrect. A current is generated when a...

Homework Statement Prove that the electromagnetic wave equation:  (d^2ψ)/(dx^2) + (d^2ψ)/dy^2) + (d^2ψ)/(dz^2) − (1/c^2) * [(d^2ψ)/(dt^2)]= 0 is NOT invariant under Galilean transformation. (i.e., the equation does NOT have the same form for a moving observer moving at speed of...

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: