When a particle of charge q and mass m enters into a uniform magnetic field B moving with a velocity v perpendicular to the direction for the field it describes a circular path of radius___________________?
Correct answer: B. R=mV/qB
- A. R=qB/mV
- B. R=mV/qB
- C. R=qmV/B
- D. R=qmB/V
Explanation
The magnetic force supplies centripetal force: qvB = mv^2/r. Rearranging gives r = mv/(qB), with radius r in m, mass m in kg, velocity v in m s^-1, charge q in C, and field B in T. The likely wrong choice is a, which is essentially the reciprocal dependence and has incorrect dimensions.
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About Charged Particle in a Magnetic Field
A charged particle moving through a magnetic field experiences the Lorentz force, which is perpendicular to both its velocity and the field. The motion may be circular or helical, with questions involving radius, angular frequency, time period, and work done. A stationary charge feels no magnetic force.
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