both involve a charge carrier undergoing centripetal acceleration thereby producing radiation from the acceleration; so what's the difference?

## Answers and Replies

The difference has to do with the speed of the particle. If it is relativistic, it is synchrotron radiation.

1 person
different but related topic: i thought all antennas were just a straight wire, so it baffled me to see my living room tube TV screen get fuzzy every time i pointed my walkie talkie straight at the TV, since, i thoguht there should be no change in the field vector in the direction the antenna is actually pointing at. However.. i broke the cover open and i find this...

http://i.imgur.com/3LKb1jd.jpg

so i immediately thought cyclotron radiation. would this be correct?

wouldn't this imply that all inductors emit RF? if this why integrated circuits get shielded?

Inductors produce magnetic fields. When fed with changing current, the field is changing, which means RF.

Baluncore
iScience said:
i thought all antennas were just a straight wire
You were wrong. Antennas are only straight wires for beginners because they are easy to explain. Any change in the distribution of conductive objects near a TV antenna will change the local field. That may null the signal to the TV antenna.

If you stretch the helical wire out to a straight line and you will find it's length is related to the wavelength. Coiling the wire makes it a physically smaller antenna without major change in antenna performance.

iScience said:
so i immediately thought cyclotron radiation. would this be correct?
No. You are wildly jumping to conclusions. When you ride a bicycle, do you also expect the wheels to generate cyclotron radiation?

iScience said:
wouldn't this imply that all inductors emit RF?
Inductors have magnetic fields proportional to the current flowing. The energy in their magnetic field is what makes them inductors. If the current varies at radio frequencies, so does the field, then RF is emitted.

iScience said:
if this why integrated circuits get shielded?
Some ICs are shielded when they need to be. Most ICs are so small that they are not susceptible to relatively long wavelength radiation. It is generally the connection cables that pick up RF.

No. You are wildly jumping to conclusions. When you ride a bicycle, do you also expect the wheels to generate cyclotron radiation?

i'm working off the idea that cyclotron radiation is radiation produced by an accelerating charge carrier. when the walkie talkie is transmitting, i assume it is doing so through its antenna; or is this also a false assumption? if it is transmitting through its antenna, the path of the charge carriers is circuler in the x-y plane which means they will undergo constant acceleration, centripetal acceleration, does this not mean that they will produce cyclotron radiation? i thought cyclotron radiation was the acceleration of charges. Or MUST it be in a magnetic field?

regardless of whether or not "cyclotron" radiation must take place in a B-field, is my proposed mechanism the correct way the antenna is transmitting its signal?

and if the rim of a bike wheel was charged, and i ride it, why wouldn't the rolling motion produce radiation?..

Inductors have magnetic fields proportional to the current flowing. The energy in their magnetic field is what makes them inductors. If the current varies at radio frequencies, so does the field, then RF is emitted.

yes i know about the magnetic field and what makes inductors, inductors. Again, if charge carriers are going in circular motion, whether it's AC or DC, the charge carriers will undergo a constant acceleration while they're in the inductor and they will produce radiation via acceleration is this incorrect?

Drakkith
Staff Emeritus
On the scale of the electrons, the wire is very very very very very straight. Cyclotron radiation, if any is actually produced, must be very very minimal.

Baluncore
The real electrons in a conducting wire are moving at walking pace or less. In your antenna element, since one end is open circuit there can be no net flow, just a microscopic oscillation. So cyclotron radiation would not be expected.

The bicycle wheel has some free electrons in the alloy rim. The Earth's magnetic field is weak and the rim is rotating at about 50km/hr. But each point on the rim is taking a pedal curve, so again there is no real rotation.

Cyclotron radiation requires that the electron be free to be deflected by the magnetic field. That is not the case when confined to a conductor.

But each point on the rim is taking a pedal curve, so again there is no real rotation.

would you explain what you meant by this for me?

will a half sine wave be emitted? i don't care about the strength of the emitted radiation i just wanna know if there will be something emitted

Baluncore
There will be no cyclotron radiation.
The electrons are not free to be deflected since they are trapped in the conductor.

There will be EM radiation from the coiled antenna.

what do you mean by be deflected? are you referring to there being no way of getting them to undergo acceleration?

Baluncore