Register to reply 
Accelerating charged particle radiation reaction 
Share this thread: 
#1
Mar2012, 05:04 AM

P: 34

It is known that if a charged particle accelerates then it emits electromagnetic wave (energy). If so then this means that the work we do on particle, W=F*s, doesn't all go to particles kinetic energy, E=0.5*m*v^2. Then this means that Newton's F=m*a doesn't hold for charged objects, particles, masses, etc.. Is that true? If yes, then what resists particle to accelerate to the speed it deserves ( F*s=0.5*m*v^2, solve for v ). I hope i could explain my point. I am sorry i ask a lot about electromagnetism but it is so damn confusing to me, i cant find peace if i dont understand it properly.



#2
Mar2012, 07:25 AM

Sci Advisor
HW Helper
Thanks
P: 26,157

hi roboticmehdi!
(try using the X^{2} button just above the Reply box ) some of the work goes into the electromagnetic field, whose energy density increases F = ma still holds, but you have to include the force from the field! however, the effect is negligible in practice … a lot less than the air resistance which we also usually ignore! 


#3
Mar2012, 10:38 AM

P: 34




#4
Mar2012, 11:59 AM

Sci Advisor
HW Helper
Thanks
P: 26,157

Accelerating charged particle radiation reaction
what would be the body with mass m in that equation? 


#5
Mar2012, 12:28 PM

P: 34




#6
Mar2012, 12:29 PM

P: 34

i dont how to do this sorry. in my upper post some of my comments are inside the quoted text. dont miss it.



#7
Mar2012, 02:21 PM

P: 34

anybody has other answers to my question ?



#8
Mar2012, 02:24 PM

P: 617

We don't typically use F = m a directly with electromagnetic waves, but it is still there in principle. We talk more in terms of energies than forces. The power radiated by an antenna, for instance, is not calculated as the force times velocity, but rather as the energy flow rate. The conservation of energy equation in electromagnetics accounts for both a force giving kinetic energy to a charged particle and also causing energy to radiate away.



#9
Mar2112, 04:10 AM

Sci Advisor
Thanks
P: 2,351

This is a problem that is unsolved in classical electrodynamics. Classical point particles interacting with their own radiation field leads to equations with weird properties, predicting among other things selfacceleration.
The best source to learn about this difficult problem is the book F. Rohrlich, Classical Charged Particles, World Scientific 2007 


Register to reply 
Related Discussions  
Classical charged particle's reaction to its own retarded field  General Physics  41  
Relativity: radiation caused by a charged particle moving through a magnetic field  Advanced Physics Homework  0  
Charged particle movement close to single charged plate  Classical Physics  3  
Does a UNIFORMLY accelerating charge radiate? What about radiation reaction force?  General Physics  1  
Radiation Reaction Force (or Self Force of charge particle)  Advanced Physics Homework  7 