Physics · Force on a moving charge in uniform magnetic and electric fields

An electron is projected into a magnetic field along the lines of force. Then

An electron is projected into a magnetic field along the lines of force. Then

  • A. there will be no effect on its motion
  • B. the electron will travel along a circle and its speed remains unchanged
  • C. the electron will follow the path of a parabola and its speed will increase
  • D. the velocity will increase in magnitude but its direction will remain unchanged.

Step-by-step solution

The magnetic force on a charged particle is given by F = q (v × B). When the velocity is parallel to the magnetic field lines, the cross product is zero, so no force acts on the electron. Therefore, its motion remains unchanged.
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