A.2.15—Magnetic force Fm
- Syllabus
- First assessment 2025
- Objective
- —
- Level
- SL
Identify Magnetic Force
Magnetic interaction
A magnetic force acts on a moving charge or current in a magnetic field. Its direction is perpendicular to the relevant velocity/current and magnetic-field directions.
Apply the direction rule
Use the stated right-hand rule or vector relationship, then reverse the result for a negative charge. Parallel motion and field give zero magnetic force in the ideal model.
Common trap
A magnetic field can change the direction of velocity without doing work on an ideal moving charge; do not automatically infer a speed change from a magnetic force.