All Questions
70
questions
0
votes
1
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50
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Simple thought experiment -> requirement for EM radiation pops out
Thought experiment (all ideal components): Two 1F capacitors wired in parallel (or ring), with open switches separating them, one cap is uncharged, and the other cap is charged with 1 Coulomb->1Volt->...
2
votes
4
answers
764
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
0
votes
1
answer
250
views
Electromagnetic Wave (Without Magnetic and Electric Field)
As I know, every electromagnetic wave has magnetic and electric field component (perpendicular to the direction of wave). I have a doubt about this, as a hot iron bar also emits EM waves, and as ...
- 11
0
votes
1
answer
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 ...
2
votes
3
answers
1k
views
How do near-field EM fields change to far-field EM waves at an antenna
What is the mechanism by which the near-field non-traveling electromagnetic fields in the vicinity of an antenna are changed into the far-field electromagnetic waves traveling at the speed of light? ...
- 249
1
vote
1
answer
146
views
Pair production
I have read following equation of pair production
Platinum + 2 gamma --> electron + positron
this equation I think obeys all laws and true.
But there are two books which are saying following ...
- 55
0
votes
2
answers
2k
views
Why electrostatic field is conservative?
I know, curl of static electric field (i.e. electric field generated by a time independent charge distribution) is zero, I know it can be derived from a scalar potential etc. But I want some intuitive ...
- 53
0
votes
1
answer
563
views
Electric waves for a static field?
I have a doubt about electromagnetic waves. Can we say that a static electric field is still composed of waves, even if they don't spread in space (as the field is static and so it doesn't evolve over ...
- 479
6
votes
3
answers
2k
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Feynman on Inverse Square Law of EM Radiation
I've been reading through (and listening to) a collection of lectures form Richard Feynman's Lectures on Physics. In lecture #2, titled "Basic Physics", he makes the following statement:
Although ...
1
vote
1
answer
90
views
Name of electric force
during a lab experiment, i noticed that a metal ball has a much harder time rolling on metal rails when their is a current passing through it and the rails. I was wondering why and if there was a name ...
- 1,473
2
votes
2
answers
154
views
Should static electricity affect a Crookes radiometer?
I've been playing around with a Crookes radiometer for fun and I happened across something I can't figure out.
I know the fundamentals of the radiometer (e.g. partial vacuum, thermodynamics, etc.), ...
- 121
0
votes
1
answer
82
views
Why don't conductive objects change color when electric dipoles are induced in them?
I was playing around with a comb, my hair, and pieces of paper when it occurred to me that inducing a dipole on the pieces of paper meant that many valence electrons previously on the side closer to ...
- 556
0
votes
0
answers
71
views
Frequency of Electromagnetic Radiations/Waves?
"A charge that is accelerated will produce variable electric
and magnetic fields. These are electromagnetic waves.
If the charge oscillates with a frequency f, then the
resulting EM wave will have a ...
- 1,441
3
votes
0
answers
162
views
Is frictional heat just electromagnetic interactions creating infrared radiation?
Example: Rub your index finger on a sheet of paper and you will feel that it will get noticeably hotter
Is the reason you feel this increase in heat (technically an increase in kinetic energy of the ...
- 283
4
votes
1
answer
639
views
Why is the susceptibility $\chi(t)$ real?
So my question is quite simple I suppose, and perhaps trivial. It is known that the frequency domain susceptbility $\chi(\omega)$ is complex, and that the two parts can be related with the Kramers-...
- 1,521