All Questions
Tagged with electricity electromagnetic-radiation
67 questions
19
votes
5
answers
18k
views
Is there any example where electric and magnetic fields are not perpendicular?
Perpendicular electric and magnetic field creates light or other electromagnetic waves. Is it a necessary property to have a perpendicular fields? If not what would happen when the fields are not ...
- 1,985
14
votes
7
answers
12k
views
Why is electricity not transmitted wirelessly?
Why is electricity not transmitted wirelessly such that we don't need to span cables on the earth's surface? As in: electricity is transmitted wirelessly from the power plant to the household.
- 2,729
10
votes
1
answer
4k
views
What’s the relationship between thermal radiation and Johnson thermal noise?
All objects above absolute zero emit radiation due to random collisions between the atoms they are made of. The spectrum of radiation emitted varies according to the temperature of the object, I ...
- 5,704
7
votes
3
answers
714
views
Applicability of the concept of voltage in electrodynamic circuits
In electrostatics, we have $$\nabla \times \vec{E} = 0$$. Hence, we can define a scalar potential $V$, where $$\vec{E} = -\nabla V$$. We know from Faraday's law that $$\nabla \times \vec{E} = -\frac{\...
- 933
7
votes
3
answers
349
views
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 ...
- 171
6
votes
3
answers
2k
views
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?
6
votes
1
answer
152
views
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 ...
5
votes
6
answers
769
views
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 ...
5
votes
4
answers
11k
views
How does the movement of electrons produce radio waves?
I'm mostly wondering about radio frequencies. I understand that voltage is the movement of electrons, and that the antenna acts as a light bulb, emitting at radio frequencies, following the reverse ...
- 151
5
votes
3
answers
340
views
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
4
votes
1
answer
151
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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 ...
- 3,256
4
votes
1
answer
1k
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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 ...
4
votes
1
answer
497
views
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
3
votes
3
answers
108
views
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
3
votes
2
answers
2k
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Why doesn't alternating current produce light while a vibrating single particle with a charge will
If a vibrating atom can produce light why can't an alternating current of electrons do the same?
EDIT: When I use the term "light" I mean all EMR
- 611
3
votes
4
answers
810
views
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 ...
- 150
3
votes
1
answer
829
views
Why does electromagnetic waves travel slower in well isolated conductor?
Wikipedia writes, that
Propagation speed is affected by insulation, so that in an unshielded copper conductor ranges 95 to 97% that of the speed of light, while in a typical coaxial cable it is ...
- 615
2
votes
2
answers
16k
views
Microwaves vs Gas or Electric Coil heating of a water boiler in a typical household
Wouldn't it be more energy efficient and or safe to use microwaves to heat our home's water boiler instead of using dangerous gas or hot electric coils that could catch other things on fire? I'm kinda ...
- 3,911
2
votes
1
answer
5k
views
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-...
2
votes
1
answer
2k
views
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
2
votes
4
answers
796
views
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 ...
- 191
2
votes
1
answer
142
views
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
2
votes
3
answers
2k
views
Producing electricity from all wavelengths of electromagnetic spectrum
Is it possible to produce electricity from all wavelengths of electromagnetic spectrum beside visible light ?Like using gamma rays or x-rays .
- 29
2
votes
1
answer
102
views
(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 ...
- 23
2
votes
1
answer
77
views
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 ...
- 425
2
votes
1
answer
119
views
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 ...
- 133
2
votes
1
answer
336
views
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
2
votes
0
answers
257
views
Alternative solar panels
I was doing a bit of thinking recently, when I stumbled on an interesting idea. In a simplified sense, solar cells function by absorbing light and converting it into electrical energy. Since visible ...
- 191
1
vote
4
answers
12k
views
Why do like charges repel and opposite charges attract? [duplicate]
Why do like charges repel and opposite charges attract?
1
vote
1
answer
552
views
What is the pressure of a gas required to ionize the gas using an electron gun?
How dense does a gas (Argon in particular ) have to be to in order to ionize it using electron bombardment and weak magnetic fields. Is there a correlation with the density of a gas and the easiness ...
- 279
1
vote
1
answer
15k
views
Why the electric bulb turns on almost instantly when the switch is closed? [duplicate]
The electron drift speed is estimated to be very low.How could there is current almost the instant a circuit is closed??
By the discussions it is known that The information about beginning of the ...
- 5,839
1
vote
2
answers
89
views
Can a laser work forever if constant electricity is provided?
Can a laser work forever if constant electricity is provided? If we take a laser and provide it with constant electricity will the reactions in the semiconductor generate photons forever?
- 1,923
1
vote
3
answers
2k
views
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
1
vote
1
answer
565
views
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 ...
- 11
1
vote
1
answer
1k
views
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
1
vote
2
answers
376
views
$\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 ...
- 2,637
1
vote
1
answer
44
views
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 ...
- 1,923
1
vote
1
answer
725
views
transfer of electricity through electromagnetic waves
Is it possible to transfer electricity from one place to another without the help of physical wires.
- 47
1
vote
1
answer
48
views
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
1
vote
1
answer
247
views
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 ...
- 11
1
vote
1
answer
1k
views
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, ...
- 714
1
vote
1
answer
288
views
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 ...
- 786
1
vote
0
answers
35
views
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 ...
- 65
1
vote
1
answer
79
views
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? ...
- 97
1
vote
0
answers
35
views
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 ...
- 111
1
vote
1
answer
716
views
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
1
vote
0
answers
97
views
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 ...
- 111
1
vote
1
answer
684
views
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 ...
1
vote
1
answer
79
views
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 ...
0
votes
3
answers
555
views
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 ...
- 1,453