Asked in FBISE Physics 2023 — Paper 1 2023Moderate

A charge is at rest in a magnetic field, then the magnetic force on charge is:

Correct answer: D. Zero

  • A. qvB sinθ
  • B. qvB cosθ
  • C. qvB
  • D. Zero

Explanation

The magnetic force on a charge is given by the Lorentz force law, which can be stated as: F=q(v×B)where:F is the magnetic force,q is the charge,v is the velocity of the charge, andB is the magnetic field.If a charge is at rest (i.e., its velocity v is zero), then the magnetic force on the charge is zero. This is because the cross product of zero (the velocity) and any vector (the magnetic field) is zero. So, even if the charge is in a magnetic field, if it's not moving, it won't experience a magnetic force.

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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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