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I know that an accelerated charge produces a changing electric field and so propogates electromagnetic waves.I want to know the reason or the mathematical reasonings.
thanks
thanks
James50 said:Imagine a skipping rope with a person at either end. If you flick the rope while the other holds it still, a wave travels along it. This wave in the rope is analogous to electromagnetic radiation, and your hand is the accelerating charge. The greater the acceleration, the stronger the wave.
So if you have a charge, just sitting there, it will just have radial electric field lines which only represent a potential to do work. Now, accelerate that charge and a kink will develop in those lines. This kink, as it moves away from the charge (at the speed of light, no less!) is propagating energy. The kink will be largest in the direction perpindicular to the acceleration of the charge.
If you want to know the maths, check out Maxwell's equations and the Poynting vector on wikipedia. Be warned, you will need to know something about differential equations and operators!
Here you goShyan said:I meant how is it that an accelerating charge produces a changing electric field.
How that can be derived from maxwell equations?
thanks
santo35 said:great...but i don't think all acclerating charges are capable of producing EM waves..coz if that was the case then all the electrons in plane current carrying wire shud produce EM waves...i think those charges which are ossilating in SHM can produce EM waves...which would thus cause harmonic variation in Electric and magnetic field ...
am i wrong ?
Would EM radiation of frequency 50 Hz get absorbed by everything? Is it true in general that the higher the frequency, the less absorption there is? I know that with 50 Hz there is less scattering (so that the sky is blue rather than red), but there should be more absorption.James50 said:You are right and wrong - wrong to think that what you said is incorrect, but right to assume it would happen. Yes, all AC currents in normal wires produce EM radiation. However, at a frequency of 50Hz under a fairly low current, the energy propagated in the EM radiation isn't too great. How do you think, for example, radio and television transmissions are sent? Using an electronic oscillator - which is effectively just an AC current (at very high frequency) attached to a great big whopping transmitting aerial.
Aren't the magnetic and electric fields of light the same strength, in Gaussian units?Remember - electromagnetic radiation (light, photons) is just a "harmonic variation in electric and magnetic field", as you put it. Light is just a an electric field (and magnetic, but it is considerably weaker)
But if you look at the electrons in a current individually, they are accelerating and crashing, but overall they have an average drift speed proportional to the current. When they accelerate and crash, doesn't this produce radiation?Of course, if you're talking about direct current, that's a little different because it is always going in one direction and is generally assumed to be at a constant current (depending on the layout of the circuit, and what you've got plugged in). Even in direct current you can get acceleration mind. But even assuming all direct current in a circuit is of constant current (direct just means unidirectional), you must still loop it back to its start point, it must still be accelerating accelerating around a centre point. Cyclotron radiation, for example, could be argued to be be DC or AC. It gives off an AC EM wave, but only because it travels DC-style around a centre.
RedX said:Would EM radiation of frequency 50 Hz get absorbed by everything? Is it true in general that the higher the frequency, the less absorption there is? I know that with 50 Hz there is less scattering (so that the sky is blue rather than red), but there should be more absorption.
Aren't the magnetic and electric fields of light the same strength, in Gaussian units?
But if you look at the electrons in a current individually, they are accelerating and crashing, but overall they have an average drift speed proportional to the current. When they accelerate and crash, doesn't this produce radiation?
James50 said:I think you should check out how Gaussian units actually work, and what their point is.
James50 said:Again, you are misunderstanding the point of Gaussian units.
An electric field is a force field that surrounds any charged object. It is created by the presence of an electric charge and exerts a force on other charged particles within its vicinity.
When a charged particle, such as an electron, is accelerated, it creates a disturbance in the electric field, causing it to propagate outwards from the particle at the speed of light. This disturbance is known as an electromagnetic wave.
The strength of an electric field is directly proportional to the acceleration of a charge. This means that as the acceleration of a charge increases, the electric field strength also increases.
Yes, an electric field can be shielded or blocked by using materials that conduct electricity, such as metal. These materials can redirect the electric field lines, preventing them from reaching a certain area.
Understanding the electric field of an accelerated charge is crucial in many fields of science and technology, such as electromagnetism, electronics, and telecommunications. This knowledge helps us understand and manipulate the behavior of charged particles, leading to various technological advancements.