All Questions
Tagged with electricity electromagnetic-radiation
67 questions
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Confusion about EM waves in a conductor, AC in wires, and skin effect
I am trying to get my head around these different points:
From Maxwell's equations we find that an electromagnetic wave in a conductor decays in amplitude with a characteristic length of about 1 cm in ...
- 197
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1
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102
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(A10) If light is an EM wave, can it interfere with electrons in a live wire, leading to a change in the wire's current?
Here's my question: If light is an electro-magnetic wave, with oscillating magnetic and electric fields, wouldn't light interfere with the free electrons flowing (slowly) in a wire, as the electric ...
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38
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If light is made up of electromagnetic waves, then if I put a magnetic close to a laser beam, shouldn't the light bend? [duplicate]
Light always moves in a straight line unless gravity acts on it strongly, but since it is made of electric and magnetic waves, shouldn't it be pulled towards different charges and magnetic, or is ...
- 439
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How does DC loses energy?
I am new to it, so please help. As I know, AC current is back and forth motion of electrons, which radiates electromagnetic waves, so there is energy radiation from power line to our home. But in case ...
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77
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What is the microscopic physics of DC voltage propagation?
When a battery is connected to a circuit the voltage appears to the circuit as half a pulse and is propagated as an em wave, as any other pulse would be. This em generation must be the result of ...
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In a van de Graaf generator, when a spark happens, is an electromagnetic wave produced? If yes, in which direction?
In a van de Graaf generator, when a spark happens, electrons moves from one globe to the other globe.
Is an electromagnetic wave produced?
If an electromagnetic wave is produced, why is it produced?
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2
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112
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Couldn't understand the reasoning on the propagation of the electromagnetic wave in the vacuum?
Since the solution of the wave function in vaccum gives two progressive plane waves $f(x-ct)+g(x+ct)$ depending on $x$ the direction of propagation, in the other side we have the $\operatorname{div}(...
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How does electric field apply force on charges?
As far as I understand magnetic field applies force on charges or charged/ magnetic materials via the electromagnetic waves(or photons) emitted by moving electrons. And electric field also uses ...
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3
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339
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Why do we use wires/conductors to transport energy?
I am currently studying Maxwell equations and I learned that copper wires are essentially just wave guides for EM waves. Why do we not use an insulator to guide the wave and transport the energy which ...
- 287
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41
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Does altitude play a role in the strength of electric fields?
After many controlled trials, I can conclude that the same device - e.g. a monitor - will emit far higher electric fields upstairs than downstairs, from the same distance, and in environments that ...
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Energy transfer with electromagnetic waves
As we know that the electrical energy is transferred via electromagnetic waves from the source to the load. My question is that, even if there is transfer of energy through the electromagnetic waves, ...
- 972
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Current produced by EM wave in circuit
I have a specific question regarding the current produced by an EM wave interacting with a simple square circuit with constant resistance $R$. Let's say the EM wave can be explained by the simple ...
- 161
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Is it okay to sleep with the wifi router next to me? [closed]
Where I sleep I have my wifi router right above me. I don't know if this is safe for my health since it emits radiation.
Some people say that it should be safe since the radiation emitted is non-...
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Is EM radiation released when metals, that have free electrons, are accelerated? [duplicate]
I have read that charged particles, when accelerated, emit Electromagnetic Radiation. This was the basis for rejection of the Rutherford's atomic model. But is this statement complete?
Metals have ...
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Can electric field pass through a charge particle so that the charge particle behind the one can get energy?
Can an electric field pass through a charged particle? As the field is energetic it would get absorbed by charge as I think 🤔. Let assume that there are two electrons one behind the other such that ...
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What is causing the acceleration of charges in an ideal TEM transmission line?
As I understand, in an ideal TEM transmission line we can set up the telegrapher equations and solve to show that the line propagates voltage and current waves.
My confusion arises when we recognize ...
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How does electric energy travel at speed of light when electron drift speed is so slow it cannot dissipate the voltage difference in that time?
Edit: Please let me clarify I read answers on this topic and I know the analogy of sound wherein although the air molecules from source don't reach you as sound, the wave pushes on neighboring ...
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Why an electron bound to a nucleus does not emit photons when accelerated?
I think electrically neutral materials do not generate electromagnetic radiation/photons when accelerated, but I might be wrong. If I am correct though, why is it that accelerated ions generate ...
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Can I describe whole Electromagnetism only with electric field $\vec{E}$?
Is it possible to write all Maxwell's equations only in terms of $\vec{E}$ (without $\vec{B}$)? The common formulation of Electromagnetism is governed by the equations below:
The Lorentz Force: $$\vec{...
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49
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Why is there an upper bound to the frequency at which an electronic device can be operated? [closed]
Why is there an upper bound to the frequency at which an electronic device can be operated? For example, the frequency of electricity that we receive at home is 60Hz (in the USA).
What will happen if ...
- 1,437
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563
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What is the equation of partial standing wave
What is the equation of a partial standing wave which is formed by adding two opposite traveling waves with different amplitudes: $y(z,t) = A\cos(\omega t + bz) + B\cos(\omega t - bz)$ .
This is ...
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79
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Point charge potential and electric field [closed]
What is the difference between the 2D and 3D electric field and the potential. Why is it that the potential increases when going from the 2D to the 3D representation but the electric field decreases? ...
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555
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Phase difference between source voltage and inductor voltage
What will be the phase difference between the source voltage and the inductor voltage? Will the two voltages be in phase or will be out of phase. How much out of phase they will be?
Note that there ...
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Why do clothes produce sounds after being in front of a computer for a long time?
Quite often, after sitting in front of the computer not moving a whole lot for a long time my upper body clothes (usually sweaters) make soft crackling sounds when moving or specially when taking them ...
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creating a varying electric field across a copper strip
Hi I am trying to create a varying electric field (by position on copper strip) across a copper strip by attempting a standing wave pattern. the following is a diagram
may I have some guidance on how ...
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1k
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Skin depth; EM wave and AC
When I google skin depth, I get the following definition,
Skin effect is the tendency of an alternating electric current (AC) to
become distributed within a conductor such that the current ...
- 455
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716
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Electric Field inside an ideal conductor
I have some doubts about the electric field inside an ideal conductor (let's call it E). Precisely, I have read two different descriptions
1) On physics books I read that the electric field inside in ...
- 1,329
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157
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What is the theoretical maximum efficiency of converting electricity to EM radiation? Is there such a thing?
It turns out LEDs can have an efficiency of more than 100%, i.e. they output more light energy than electrical energy goes in. The 'missing' energy is taken from their thermal energy so the LED cools ...
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2k
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Skin Effect Explanation
I do not understand some things about the Skin Effect.
Its Wikipedia definition is:
Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
- 1,329
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What is the theoretical maximum efficiency for LEDs?
Whatever efficiency you want to give in converting electricity to light. I'm guessing it would depend on the type of LED. I imagine limitations come from various reasons. It would be cool if there ...
user234190
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Why doesn't electric field of an electromagnetic wave cause an electric shock?
An electromagnetic wave can have an electric field magnitude of more than 1000 V/m, which is a very high potential difference. When the light shines on you, why don't you feel an electric shock?
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810
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How does an antenna capture the energy of EM radiation?
I am having trouble reconciling the descriptions I have read of how antennas work to recieve and transmit radiation.
My simple understanding is that in recieveing the oscilating electric field of an ...
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247
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Electric force between two parallel plates one of which got a rough surface
So if I have two parallel metal sheets separated by 0.1 meters with air as a dielectric with a breakdown strength of 3MV/m and I'm applying a voltage pulse that goes from 0 to 100kV in few ...
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4
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796
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Is the vacuum permittivity a result of defining other units first?
From Coulomb's law
$$F=\frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}$$
If instead we defined the charge of a coulomb to be $\sqrt{\epsilon_0}$ times it is now, the force would be exactly the ...
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Could the tether of a space elevator be used as a single-wire transmission line?
If you're unfamiliar with single-wire transmission lines: https://en.wikipedia.org/wiki/Single-wire_transmission_line
It seems that a material with high conductivity (eg: certain configurations of ...
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38
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Does power dissipate on real conductor when charge move from charged object to neutral charged object?
for example we have charged sphere and we have neutral charged sphere
After we connect them with real conductor (few Ohm resistance) some charge will move from charged sphere to neutral sphere.
Will ...
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Do the wires having AC current emit EM waves? [duplicate]
When ac current is passed through a wire, the electrons in the wire oscillate to and fro in the wire (due to change in polarity of current in the wire). If the ac current is of frequency, say 50Hz, ...
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Toroidal shaped Tesla Coil
Since toroidal shaped transformers perform better than conventional E core transformers. Would a Tesla Coil that is shaped in a toroidal shape perform better than Tesla coils that is shaped ...
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684
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How does current flow in a conductor if the electric field in a conductor is always 0? [duplicate]
How do EM waves propagate inside waveguides made of conductors and how does current flow inside a conductor from a high voltage to a low voltage if the Electric field inside a perfect conductor is = 0 ...
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1
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288
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Electromagnetic shielding with metal box and wire inside
I want to know if this model will have a good electromagnetic shielding or I mean it will have low radio waves losses. There is a box of aluminium foil let say 0.5x1x0.1m (50 to 100 to 10 cm) and ...
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Power losses for electromagnetic waves radiation in copper wire with high frequency current [closed]
How to calculate electric power losses to radiation of electromagnetic waves in copper wire with high-frequency current?
For example, I have a copper wire with known diameter and length and I send ...
- 786
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79
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How do you make electricity from the whole EM spectrum? [duplicate]
If we can make electricity from visible light then why can't we make electricity from all of the EM spectrum? If someone had an antenna or a plate of some sort to attract electromagnetic waves and ...
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2
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$\pm$ sign in electromagnetic wave ratio of $E$ and $B$ for regressive/progressive case
I found on textbook that the magnitude of electric field $E$ and magnetic field $B$ in a plane electromagnetic wave are always related by the fact that
$$\frac{E}{B}=\pm v$$
Where $v$ is the ...
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How do I find the intensity of this radio wave?
Now, I'm not sure if this is enough information to go off, but I'll give it a shot.
I'm trying to find the intensity of an electromagnetic wave using the formula $\frac{1}{2} c \epsilon_0 E_0^2$, ...
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What happens to wave energy if i excite wave guide with frequency below than cutoff?
Suppose I excite waveguide with frequency less than cutoff frequency. According to solutions of Maxwell equation energy of the wave must decay exponentially. Where does the energy disappear or lost in ...
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Why isn't the electronics in an EMP gun destroyed when it is fired?
Why isn't the electronics in the EMP gun destroyed along with the surrounding electronics? I have been researching electro-magnetic pulses and am confused with how the electronics inside such a gun ...
user126665
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How is it possible to even develop any current in an inductor?
Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as
$$V= -L\frac{di}{dt} -iR,$$
where $L$ is the inductance of inductor and $R$ is its ...
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3
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108
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Radiation due to current
Generally we equate change in potential energy to change in kinetic energy but in case of a charged particle like electron this is inconsistent. Consider a case: An electron(of charge e)from rest is ...
- 522
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Can we use a photon to use it as a changing field in an electric generator? [closed]
In an electric generator we use a changing magnetic field to create electricity. But what if we use a photon's oscillation of EM waves to generate electricity in a metal wire as we do in an electric ...
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What is the frequency of each of the moving electrons in a DC current?
I know that the DC current has 0 frequency. But what about each individual moving electron that makes up that DC current? Of course there has to be a frequency as all moving electrons are vibrating at ...
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