Charged Particles in E and B fields

If the charged particle is NOT moving then it will not experience a force in a B field. In an E field the force is calculated using F = E q where E is the strength of the field and q is the charge.

If the particle is moving then it will experience a force in both types of field. A moving charge constitutes a current and these do experience forces in B fields.

The direction of the force on a moving charge in a B field is found using Fleming's left hand rule. However, as the particle is deflected the direction of its velocity changes, and therefore so does the direction of the force.

Electric Field

  • The direction of the force does not change
  • The particle accelerates in the direction of the field
  • The path is parabolic
  • The particle loses EPE and gains KE

Magnetic Field

  • The force is always at right angles to the velocity
  • The acceleration of the particle is centripetal
  • The path is circular
  • No energy is transferred. The particle does not speed up.