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0

I suppose your question corresponds to a DC current. In that case, if you have a solenoid made with ferromagnetic wire, you have at the core of the solenoid the same field than in a copper solenoid. But while the magnetic field INSIDE de copper is very small, when using ferromagnetic wire the B field inside it is great. In DC circumstances there are no more ...


0

I suppose that the moving wire is a closed circuit and that the magnetic flux enclosed is time-dependent. The Faraday’s law is of course always applicable. The current will not be infinite. Yes R=0 but, what about the self inductance L? It is never zero, in such a manner that the total E field will be null. If you make the calculations the electric field in ...


0

You must obtain the magnetic field due to the solenoid according to the approximate calculations according to its dimensions. If the magnet is small you can easily found the torque, and also the force when it is in a region of non uniformity.


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There are no sextupoles in the expansion! All $n$-poles have numbers $n$ which are powers of two, i.e. $n=1,2,4,8,16,32,$ and so on. The case $n=1$ is the monopole, the actual charge. Its electric field goes like $1/r^2$ – let's adopt the electric notation. The $n=2$ dipole is a pair of $n=1$ charges of opposite signs, shifted relatively to each other. The ...


2

I'm not exactly sure about your procedure, maybe adding some context would help, however spherical harmonics are represented by two numbers: $Y^m_\ell$. If you go to the third order ($\ell=3$) you have for $m=\pm1,\,\pm3$ a clear sextupolar shape: In accelerator physics the sextupolar term is extremely important and we also have dedicated magnets to ...


1

In special relativity, in the rest-frame of the proton, the moving magnet m appears as a magnet m’ and an electric dipole p’. The electrostatic E field created by the proton makes rotate this electric dipole, actually the magnet. And the E’ created by the electric dipole is the responsible for the force the proton experiences. Remark that you will not found ...


0

the trm "weight" in its own mean the net mass of the metal + the gravitational force. we see that the non-metals are not attracted towards magnets. earth, being a giant magnet, attracts metals only. thus, the weight of the non metals is mass + gravitational force on the other hand, metals have higher masses too. so their weight is mass + gravitational force ...


1

There are often material limits to how high the magnetic flux density can get. So no matter how much more current (not voltage) you apply you'll find the magnetic field stops increasing. Notice how the curves start to flatten out for different materials (reference): The relation between the magnetizing field H and the magnetic field B can also be ...


1

Yes, a sheet of a superconducting material will act as a magnetic screen because magnetic fields cannot penetrate into superconductors. Actually a plate of a simple ferromagnet is not a bad magnetic screen and will block most of the magnetic field, though not all. As Jon Custer points out, there is a high relative permittivity ferromagnet called mu metal ...


0

In a homogeneous field, the paramagnetic material does not move - why should it? An acceleration towards permanent magnets just happens as their field is not homogeneous. You (partially) align the magnets in the paramagnetic material with the magnetic field and bring them closer together, this releases energy. If you want to separate the objects again, you ...


1

A paramagnetic material is something that has a magnetic field even without the presence of an external field, but the external net effect is roughly zero. The internal atoms or molecules of the substance have magnetic diopoles meaning the substance itself is made up of billions of tiny magnets. The thing with paramagnetic materials is these dipoles are ...


0

The glass bob will reach the ground earlier as acceleration due to gravity is independent of a falling body's mass. Being an insulator, no induced current is developed in it due to Earth's magnetic field.


1

You should write down all the equations of you LC circuit and that may help. The short answer is that when you close the switch and let current flow out of the capacitor, it can't flow right away because the rapidly changing current sets up an opposing voltage in the inductor. V = L di/dt And so the current increases slowly, reaching a maximum (as you ...


1

As the voltage between the capacitor's plates decreases, so should the current flowing through the circuit. I don't follow your reasoning here. Recall that, for an ideal capacitor, we have: $$i_C = C\frac{dv_C}{dt}$$ In words, the current through the capacitor is proportional to the rate of change of the voltage across, not the instantaneous value ...


0

I assume the first part, up to But how exactly does it happen? defines and explains your question, and then you show what you think about it so far? It looks like the point where it goes wrong is about what the inductor does. There is nothing about "split-second" and relativistic, it behaves in a pretty symmetric way to the capacitor. It's "dynamic" ...


0

I'm not completely clear what you are asking, but isn't this just an instance of elastic scattering? i.e. the dipole oscillates in phase with the electric field of the incoming wave and emits dipole radiation with the same phase. The example I'm familiar with would be Thomson scattering from free electrons, which oscillate like classical electric dipoles. ...


0

Using the Gauss's law (see this Link), the solution is as follow, $$ \Phi (r) = \left\{ {\begin{array}{*{20}{c}} {\frac{q}{{4\pi \varepsilon {r_1}}}\,\,\,\,for\,\,\,r \le {r_1}}\\ {\frac{q}{{4\pi \varepsilon r}}\,\,\,\,for\,\,\,{r_1} \le r \le {r_2}}\\ {0\,\,\,\,\,\,\,for\,\,\,r \ge {r_2}} \end{array}} \right. $$


0

You can use a Boltzmann distribution at any point in time to describe the density of electrons as a function of position (or potential) only if there are e-e collisions. These collisions thermalize the distribution of electrons and allow you to define a temperature. The distribution you start off with (I assume this is what you mean by "initialization") ...


1

Forces do not always induce motion. Instead, they can be counteracted by other forces. In this case, we can clamp the wires into a form. Any force created by the current is counteracted by the form, so the wires don't move. Steady current, static wires, constant force. Since there is no motion in this case, there is no work done. You are correct that ...


0

Although Logan wrote a correct solution, I find it is almost always helpful to draw yourself a diagram: Vector $\vec v$ is the velocity, and $\vec B$ is the magnetic field. You want to get $\vec p$, which requires you to add $\vec m$ to $\vec v$. Thus the problem is reduced to finding $\vec m$, which is the projection of $\vec v$ onto $\vec B$. This can ...


0

Yes, electromagnetic waves do indeed propagate through continuous induction. In fact, this was the brilliant feature that Maxwell added to the theory that allowed him to write down equations that can be formed into wave equations. Faraday had shown that changing magnetic fields induce electric fields, which we now write as $$ \nabla \times \vec E = - ...


-1

Well actually the electric field never propagates. Yeah it's true the e-field just inducecs a magnetic field which actually propagates and when it reaches another antenna it reproduces the same current that made it (this is how really a chagigng m-field produces a changing e-field and vice versa). Then this induced e-field again produces another m-field. ...


1

Well most texts tell you that light is an EM wave and will give you an image of a sine wave and then they start to define things like frequency, amplitude etc., leaving you to think that EM waves are like that zig-zag thing on the graph. But actually in nature what oscillate are the fields. The E-field, i.e. a region around a charged particle. When a charged ...


1

This is just a vector projection problem. The fact that one of the vectors happens to represent a magnetic field is irrelevant. The component of velocity perpendicular to the magnetic field is the total velocity minus the component parallel to the magnetic field. I.e., it's the velocity minus it's projection in the direction of the magnetic field (also ...


0

To accelerate charges you use directly or indirectly EM fields. In accelerator tubes directly, for physical bodies indirect with surface electron-electron interaction. Part of this EM effect escape at the same moment and you get radiation. Same situation when the particles moved in circles or stopped. Writing this I realize that it could be explaint in ...


0

Reading in the disclaimer section: The authors of this website are not responsible for ridicule, which can cause yourself by an effort to reproduce the devices described here. The authors of this website are not responsible for the time you may waste reading this website. They are also not responsible for the time you may waste by trying ...


1

As Wikipedia clearly lays out, the concept of a free energy generator - a machine that will perform work on external systems eternally and without needing external intervention - is inconsistent with either the first or the second law of thermodynamics. There exist, as yet, no credible and reproducible experiments that shed any type of doubt on either of ...


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You should read the (rather funny) disclaimer on that site: This website presents a serious risk of damaging your self-confidence in case you decide to take any content of this website seriously and try unsuccesfully to utilize it any usefull way. "Free energy" is not possible due to energy conservation.


8

Imagine the field lines of a point charge - they all point outwards of the charge in a radial direction. Now consider the following statement: the change of the field does not propagate instantaneously, but it has to propagate through local interaction. When we nudge into the charge, a ripple in the field propagates to tell the other field lines "hey guys, ...


1

I think understanding cerenkov radiation qualitatively might help a bit. Cherenkov radiation results when a charged particle, most commonly an electron, travels through a dielectric (electrically polarizable) medium with a speed greater than that at which light would otherwise propagate in the same medium. Moreover, the velocity that must be ...


6

Your second method is correct. To compare, say, the magnetic field with what you find in Jackson, you really need to realize that there's an assumption that you have unit basis vectors there, and that the cross product is actually a hodge dual (which will invoke factors of the square root of the determinant of the metric). These will make direct ...


0

It is incorrect to state that The magnet is only braked by the friction of the axis and the air. It is not clear to me exactly what you're proposing, but whenever you deliver electrical energy to some external system you will slow down the rotation of the coil. This is usually through an inductive torque caused on the rotating coil by the currents that ...


0

The second form is the way in which the metric was written in the age of Kaluza and Klein. Why? out of embarrassment. If you keep the scalar field when considering the action you get an scalar. That was an undesired feature those times and that's why they hid it making it constant (actually they made it equal to 1). Now, is there a reason why the first is ...


1

The electric field inside a conductor should be zero. But this is not necessary flux entering it should be equal to flux leaving. Thats why we get this answer.


2

The fraction of a wavelength used for antenna design is driven by the need to transfer the maximum power to and from the antenna. This is done by matching the impedance to the antenna. The standard $\lambda/2$ value is where the impedance resonates and there is no reactance, just real resistance, making the antenna easier to match to. This is the reason ...


0

Given that this was a Physics class, it is likely that the complexities of antenna design were understated or ignored entirely. Indeed, it is part art (experience) and part sophisticated analytical and numerical modeling. With the above in mind, the "best" simple antenna one can construct is either a half-wavelength ($\lambda/2$) dipole antenna (center ...


2

One: I honestly don't know. I was already hard for me to find this experiment in german - although german is my mother tongue. ^^ I finally succeeded with Ringentladung, which I tried to translate into english but the only thing I could find is this. Maybe a native speaker can help here? Two: The electric discharge - which causes the gas in ...


2

I immediately have an issue with the idea of the magnetic field "moving." But you don't need such an idea. Assume that, in the lab frame, there is a uniform B field pointing 'up' which is to say that at every spatial point in the lab, the value of the B field is $$\vec B = B\hat z$$ Also, assume that the E field is zero everywhere in the lab ...


1

There are the EMS, an add-in to Solidowrks, so you can simulate in 3D: (payed). Others: Amperes Quickfield MagNet Open source: MaxFEM


1

The lightning rod is based on two principles theorized by Benjamin Franklin. Lightning dissipation theory, and lightning diversion theory. Lightning Dissipation Theory This theory says that if you point a pointy metal object toward a polarized cloud, the metal object will be able to bleed off some of the energy from the cloud. Thus preventing a lightning ...


0

As many people have already said in their answer, if you ask yourself what is the force between any two charged particles which have some velocities at some time in the frame of reference of the lab, then what you find is the Lorentz force: $\mathbf{F} = q(\mathbf{E} + \mathbf{v} \times \mathbf{B})$. Now, the problem is when you try to resolve the dynamics ...


1

Suppose in some reference frame S, we have two stationary charged particles, $q_1$ and $q_2$. The force experienced by the first particle due to the second is given by $\textbf{F}_{12} = k \frac{q_1 q_2}{r^2_{12}} \hat{r}_{12}$, where $k$ is Coulomb's constant, $q_i$ is the charge of the respective particle, $r_{12}$ is the distance between the two ...


0

I would leave special relativity out of the picture. I mean: magnetism is a relativistic effect, in the sense that it pops out from the application of (special) relativity to electrostatics, but their relationship is more conceptual and may deserve a new question entirely devoted to the matter. Long story short, you don't need special relativity to ...


0

Lorentz's force is acting on the charge $$F = q(E+v\times B)$$ If the charge is moving in an uniform electric field $E$, there will be no $B$ and the force is $F = qE$. In the case of a non-uniform electric field (e.g. a point charge), the electric field at the charge will change in time and thus, by the Ampere's law, a $B$ will be induced. But usually (in ...


3

Coulomb's law is not precisely true when charges are moving-the electrical forces depend also on the motions of the charges in a complicated way. One part of the force between moving charges we call the magnetic force. It is really one aspect of an electrical effect. That is why we call the subject "electromagnetism." There is an important general ...


0

Yes, Coulomb's law is accurate for moving charges. It is applied in, for instance, molecular dynamics simulations.


0

This may be cheating, but I think the problem is easier if you use conservation of energy. If you set the gravitational potential energy reference to the height of m1, then initially you have $$ U_i = k\frac{q^2}{d}. $$ The final energy will have a gravitational potential energy and an electrical potential energy: $$ U_f = mgh + k\frac{q^2}{r} $$ A bit of ...


0

I worked the problem out a ways and it involves quite a bit of tedious algebra. The technique I used was to include the electric force in the Fx and Fy equations by looking at the angle that $ \hat{r}$ (the vector between the two charges) makes between the charges. For example, the equation i came up for Fx is $T_x - \frac{Kq^2}{r^2} \cos{\theta} =0$ where ...


2

We don't really understand why charge is quantized. Nor we do know if there ought to be magnetic monopoles. These two things seem linked. Dirac gave an argument for charge quantization in the early days, but this presupposed the existence of a magnetic monopole. In Maxwell's equations, it would be completely natural to imagine the existence of magnetic ...


0

An electromagnetic field, in order to start being harmful to humans, would have to be strong enough to dictate ion motion in our nervous system, and electrical signals to and from the brain. After all, everything we experience is the result of electrical signals. I took 16 Tesla ( magnetic field units ) to levitate a frog. I would assume that's also probably ...



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