Charged particle in a magnetic field
Send a positive ion into a uniform magnetic field and watch the Lorentz force bend its path into a circle.
When the velocity is perpendicular to the magnetic field, the Lorentz force is always perpendicular to the velocity: it changes only the direction of motion, not the speed, so the particle moves in uniform circular motion. The orbit radius grows with mass and speed, and shrinks as the charge and the magnetic flux density increase.
Orbit radius vs. flux density
The particle's speed, mass and charge use the current settings.
Think about it
With the particle speed and all other conditions unchanged, if the magnetic flux density is increased to 2 times its original value, how does the orbit radius change?
The orbit radius is halved. From r = mv/(qB), the radius is inversely proportional to the magnetic flux density B.
Model assumptionsNon-relativistic positive ion · Velocity always perpendicular to the uniform field · Gravity and electric fields neglected · Orbit radius drawn on a square-root scale
Data log
Set the parameters and click “Record data”. Record several rows with different parameters to plot their relationship and fit a straight line; pause and record at different times to study how a reading changes with time.