Under the influence of a uniform magnetic field,a charged particle mov...
The time period of the charged particle is
given by

Thus, time period is independent of both v and R.
View all questions of this testUnder the influence of a uniform magnetic field,a charged particle mov...
Understanding the Motion of Charged Particles in a Magnetic Field
When a charged particle moves in a uniform magnetic field, it experiences a force known as the Lorentz force, which acts perpendicular to its velocity. This force causes the particle to move in a circular path.
Key Factors in Circular Motion
- Centripetal Force: The magnetic force acts as the centripetal force, keeping the particle in circular motion.
- Magnetic Force Formula: The magnetic force acting on a charged particle is given by F = qvB, where:
- q is the charge of the particle,
- v is the speed of the particle,
- B is the magnetic field strength.
- Centripetal Force Requirement: For circular motion, the required centripetal force is given by F = mv²/R, where:
- m is the mass of the particle,
- R is the radius of the circular path.
Deriving the Time Period
When equating the magnetic force to the centripetal force:
- qvB = mv²/R
From this, we can derive the relationship for the radius R:
- R = mv/(qB)
Now, the time period T of one complete rotation is given by:
- T = Circumference / Speed = (2πR) / v
Substituting R from the earlier relationship:
- T = (2π(mv/(qB))) / v = (2πm)/(qB)
Conclusion: Independence of T
- Dependence: The time period T depends solely on the mass of the particle (m), charge (q), and magnetic field strength (B).
- Independence from v and R: This shows that T is independent of both the speed (v) and the radius (R) of the circular path.
Thus, the correct answer is indeed option B: the time period of rotation is independent of both v and R.