# Tagged Questions

The classical theory of electric and magnetic fields, both in the static and dynamic case. Also covers general questions about magnets, electric attraction/repulsion etc. Distinct from electrical-engineering.

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### Possible dangers of power lines radiation, wi-fi and gsm technology [closed]

I'd like to know more about the topic mentioned in the title. I have 3 questions. I'd be happy to hear your thoughts on any of those. So if high voltage power lines can cause harm to a human in some ...
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### Where does the permittivity of free space constant come from

Does anyone know why the permittivity of free space is defined as: $\epsilon_0 = \frac{1}{\mu_0 c^2}$ ?
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### How much does the magnetic force change in a solenoid with the distance between turns?

I was looking for answer in my physics book and in Internet but not. I guess that more distance should be an smaller magnetic field but I do not know how much.
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### Biot-Savart for current carrying wire

A homework question has made me doubt my understanding of the application of the Biot-Savart law. Question: The magnetic field 43.0 cm away from a long, straight wire carrying current 5.00 A is ...
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### Different frequencies working together

How do the different waves of EM spectrum present in the environment not interfere with each other? If they do, how does everything work properly? The radio waves of mobile phones and wi-fi work ...
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### For AC current is it better to have a solid or a strandled wire?

For alternating current in wires there are two effects that make energy losses (increase effective resistance): Skin effect which comes since alternating current produces alternating magnetic field ...
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### Equation of Trajectory [closed]

I was reading about Lorentz force law and motion of a charged particle under Electric field or magnetic field and I understood how they move in it. But as I was moving further I came across the ...
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### How does the magnetic field gain energy through the induced non-conservative electric field?

This is a further question derived from this question about storing energy in an inductor. The accepted answer showed that, during the current increasing, it is the induced non-conservative electric ...
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### Near Infrared for distance determination

Would near-infrared be an efficient frequency to use in determining the distance from the source of the infrared signal to an object, maybe in the range of 5 to 20 meters away? I need a formula for ...
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### Why does the superposition principle work? [closed]

I am reading Feynman volume 2. (I was reading Griffiths at first.) I don't really understand why the superposition principle of electrical forces (or fields) works. Is there anything deeper in that? ...
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### Difference between spin and polarization of a photon

I understand how one associates the spin of a quantum particle, e.g. of a photon, with intrinsic angular momentum. And in electromagnetism I have always understood the polarization of an EM wave as ...
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### In which direction due to a polarizing grid the photon's electric field is oriented?

After a photon passes the slit, is it's electric field oriented perpendicular or parallel to the slit and why this is so?
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### What topics do I need to study electromagnetism on the quantum scale? [closed]

What topics do I need to study (in order) so that I can study electromagnetics on the quantum scale? What is the name of the discipline studying electromagnetism on the quantum scale? Do I need to ...
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### How are the Lorentz force, Maxwell's third law and Faraday's law of induction clasically related?

Faraday's law of induction can be used in any situation where the magnetic flux is changing through a closed conducting loop. While giving the correct answer, it seems to me that for the following ...
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### Is there a material that could “convert” near infrared frequency to infrared?

I have a laser with a wavelength of 650 nm (visible red light) and was wondering if there is some sort of material that could be used to absorb and disperse a different frequency of light around (900 ...
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### Does a magnetic field do work on a moving rod?

In a case such as this one, my textbook says that I might be tempted to think the magnetic force is doing work (against the moving rod). It then says this isnt the case because "charges move ...
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### Speed of an electromagnetic soliton in free space

What is the speed of an electromagnetic soliton in free space? Is it equal to 'c' ? P.S. My understanding of the Fourier transform says it's not.