Objective
Launch a charge into a uniform magnetic field and watch it curve: F = qv x B bends the path into a circle whose radius is set by momentum and field strength.
The idea
A charge only feels a magnetic force while it is moving across the field. That force never speeds it up - it only bends its path, curving it into a perfect circle.
Try this
- 1Send a charge into the field and watch the circular arc.
- 2Increase the speed and see the circle grow.
- 3Increase the field and see it shrink.
- 4Flip the charge sign and watch it curve the other way.
Watch for
- The magnetic force is perpendicular to both velocity and field.
- Radius r = mv / qB: faster, lighter, weaker field -> bigger circle.
- The force does no work - speed never changes, only direction.
- Negative charges curve opposite to positive ones.