The magnetic force on a moving charge does no work on it because the force is
Correct answer: B. always perpendicular to the velocity
- A. very small
- B. always perpendicular to the velocity
- C. always opposite to the velocity
- D. not a real force
Explanation
Work is the dot product of force and displacement, and a force at right angles to the motion contributes nothing, so the kinetic energy and speed of the particle never change. Only the direction of travel is altered. This is why a magnetic field can steer a particle beam but cannot accelerate it, which is the job of the electric field in an accelerator.
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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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