Free Charge Moving in Uniform Magnetic Field
- Since the magnetic force always acts at right angles to the charges motion, the magnetic force can do no work on the charge. The B-field cannot speed up or slow down a moving charge; it can only change the direction in which the charge is moving.
- The general path of a moving charge in a constant magnetic field is that of a helix with its axis parallel to the direction of the magnetic field.
If you stand in such a way that you are looking directly into the oncoming magnetic field, the a positively charged particle will be seen to rotate in clockwies circle where as a negatively charged particle will rotate in counterclockwise circle. See Charge Particle moving in a Uniform B-Field IP Simulation..
- The component of velocity of the charged particle that is parallel to the magnetic field is unaffected, i.e. the charge moves at a constant speed along the direction of the magnetic field.
- If the particle has a component of velocity parallel to the magnetic field, then its circlular motion will drift at a constant speed (equal to that of its parallel-velocity component, vll) along the magnetic field producing an overall helical motion.
- The component of the velocity perpendicular to the magnetic field,
is what cause the particle to executes uniform circular motion perpendicular to the magnetic field.
- The radius of the circular can be found by equating the magnetic force on the charge with the centripetal force.
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B-Field is into Paper
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- Negatively charged particles circulate in the opposite direction as positively charged particles. The direction can be found using the right-hand-rule applied to the perpendicular component of the velocity. See Charge Particle moving in a Uniform B-Field IP Simulation.
- The angular frequency w at which a charged particle revolves about the magnetic field (normally called the cyclotron frequency) is independent of the speed of the particle.
