What kind of effects does a magnetic field and magnetic force have on the motion of a charged
particle inside the magnetic field?
At the heart of the most important machines that exist in the world today, such as
printers, microwaves, and disk drives, there exist magnetic force and magnetic field. Magnetic
forces act quite similarly to electric forces as a charge first produces a field around itself,
allowing forces to arise because of this field. However, unlike electric forces, magnetic forces
and fields only exist for a particle that is in motion. This is due to magnetic fields acting
perpendicular to charges instantaneous direction of a motion. Since only moving charges can
have perpendicular forces asserted and magnetic field does no work on the charge, the charge
must be in motion for the magnetic field to have effect on its direction and motion. Once the
charge is in motion within the magnetic field, it can finally respond to this field and experience
magnetic force.
As previously stated, since the magnetic force never has a component parallel to the
particle’s motion, it can never do work on the particle even if the magnetic field is not uniform.
This means that the magnetic force can only affect the direction of a charge, with Newton’s laws
determining its motion. Because of the magnetic forces that the charge experiences in a magnetic
field, the charge will move in a plane perpendicular to a uniform magnetic field. This allows for
a charge that has an initial velocity that is perpendicular to the magnetic field to move in a circle
while maintaining constant speed. It was observed that for particles that has an initial velocity
that is not perpendicular to the uniform magnetic field, the motion is of a helix. This helical path
was the result of the particle having the components of both parallel and perpendicular to the
magnetic field. For charged particles in a nonuniform magnetic field, the motion is said to be
more complex and fluctuating. Particles can end up oscillating back and forth between two
different magnetic fields if it exists in a nonuniform magnetic field.
Studying magnetic field and magnetic forces gave me a better idea on how some of the
machines that I frequently use heavily depend on magnetism in order to work properly. For
example, by utilizing the fact that magnetic forces don’t affect the particle’s velocity or
magnitude, mass spectrometers are able to measure the precise mass of a molecule using the
equation of circular orbit in a magnetic field. Because these mass spectrometers block all ions
except those with pre-determined velocities, the radius of the ions can be determined once it
passes through the initial ‘test.’ Through this machine and the concept of magnetism, I am able
to get the precise mass of a compound and determine if a certain chemistry experiment worked
or not. Magnetic force’s effect on particles also allowed me to view Aurora Borealis during a trip
to Alaska. Due to charged particles from the Van Allen radiation belts being able to enter the
atmosphere after being trapped by the Earth’s nonuniform magnetic field, I was able to keep a
great memory from that summer trip and cross something off my bucket list.