Why Does Cyclotron Frequency Depend Only on Magnetic Field Strength?

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SUMMARY

The cyclotron frequency of a charged particle is determined solely by the magnetic field strength (B), charge (Q), and mass (M) of the particle, as described by the equation F = BQ/(2πM). The frequency does not depend on the particle's speed or radius, as the magnetic field provides the necessary restoring force for the particle's motion. The electric field serves only to increase the amplitude of the particle's oscillation, while the period of oscillation remains constant regardless of amplitude. This relationship highlights the unique role of the magnetic field in governing the dynamics of charged particles in motion.

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  • Understanding of cyclotron motion and frequency
  • Familiarity with the concepts of magnetic fields and forces
  • Basic knowledge of simple harmonic motion (SHM)
  • Proficiency in algebraic manipulation of physical equations
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  • Study the derivation of the cyclotron frequency formula F = BQ/(2πM)
  • Explore the principles of simple harmonic motion (SHM) in the context of charged particles
  • Investigate the effects of varying magnetic field strengths on particle motion
  • Learn about the role of electric fields in charged particle acceleration
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Physicists, electrical engineers, and students studying electromagnetism or particle dynamics will benefit from this discussion, particularly those interested in the behavior of charged particles in magnetic fields.

Davidmb19
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According to the equation F=BQ/2pieM the frequency depends on the magnetic field and not the speed or radius of the particle. Can someone please explain why?

B= Magnetic field strength Q=Charge M=Mass

I think it's because of the force felt due to magnetic field so the time it reaches the dees depends on how large the force is eventhough, there's an electric field that accelerates the particle.
 
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It's an example of SHM. The frequency of SHM does not depend on the amplitude.
 
So why does it depend on the magnetic field strength? Is the reason similar to I said?
 
Davidmb19 said:
So why does it depend on the magnetic field strength? Is the reason similar to I said?
I didn't understand that part. What are 'dees' here?
 
haruspex said:
I didn't understand that part. What are 'dees' here?
 
Interesting video, but there is one serious error in it. Where it says va is the voltage, it means va is the frequency of the voltage.
Davidmb19 said:
I think it's because of the force felt due to magnetic field so the time it reaches the dees depends on how large the force is, even though there's an electric field that accelerates the particle.
So your question here is why does the natural frequency depend on the magnetic field strength but not on the electric field strength.
Again, by SHM analogy, the magnetic field supplies the 'restoring force', like the modulus of a spring. But you need to be careful with the analogy because the perturbation being restored is the particle's velocity, not its position.
The reversing electric field is not required to produce the SHM. Once circulating, a charged particle would tend to cycle around perpendicularly to the magnetic field at constant speed and frequency. The electric field only serves to raise the amplitude each cycle, and, as discussed, the amplitude does not change the period.
Alternatively, we can throw the analogies away as potentially misleading and just look at the dynamics. If the particle is circling with speed v at radius r then the centripetal force required is mv2/r. The radial force supplied is qBv. Equating these gives v/r = qB/m. Since the path length is 2 pi r, the period is 2 pi r/v = 2 pi m/(qB).
 
haruspex said:
Interesting video, but there is one serious error in it. Where it says va is the voltage, it means va is the frequency of the voltage.

So your question here is why does the natural frequency depend on the magnetic field strength but not on the electric field strength.
Again, by SHM analogy, the magnetic field supplies the 'restoring force', like the modulus of a spring. But you need to be careful with the analogy because the perturbation being restored is the particle's velocity, not its position.
The reversing electric field is not required to produce the SHM. Once circulating, a charged particle would tend to cycle around perpendicularly to the magnetic field at constant speed and frequency. The electric field only serves to raise the amplitude each cycle, and, as discussed, the amplitude does not change the period.
Alternatively, we can throw the analogies away as potentially misleading and just look at the dynamics. If the particle is circling with speed v at radius r then the centripetal force required is mv2/r. The radial force supplied is qBv. Equating these gives v/r = qB/m. Since the path length is 2 pi r, the period is 2 pi r/v = 2 pi m/(qB).

Sorry for the long response. Now that I think of that way it does make sense. Thanks.
 

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