Physics HL · Chapter 19: Motion in Electric and Magnetic Fields
Chapter 19 Wrap-Up
Consolidate path classification, force-balance logic, and q/m workflows into one reliable exam method.
Estimated time: 8 minutes
One Workflow That Solves Most Chapter 19 Problems
Start with geometry: draw v relative to E and B. Then classify each velocity component: electric fields change components parallel to E, magnetic fields curve components perpendicular to B, and crossed-field setups combine both. Choose equations only after that classification. This order reduces most problems to familiar mechanics templates.
For electric-only stages, use both kinematics and energy for cross-checking. For magnetic-only stages, remember speed is unchanged unless another force is present. For crossed fields, compare v with E/B first; this instantly predicts deflection direction before arithmetic.
Chapter 19 Key Takeaways
- Uniform electric fields produce straight or parabolic motion depending on entry direction.
- Uniform magnetic fields produce straight, circular, or helical trajectories depending on velocity decomposition.
- Magnetic force does zero work and cannot change kinetic energy by itself.
- Circular-motion radius in B is r = mv/(|q|B), with period T = 2pi m/(|q|B).
- Crossed-field selector condition is v = E/B when electric and magnetic forces oppose.
- Combining electric acceleration and magnetic bending gives q/m extraction and beam-species separation.
No new simulation is added in this wrap-up because this stage is synthesis. Re-run the chapter lab in all three modes and predict direction, radius, and energy trend before reading metrics; prediction-first practice is the fastest way to lock in field-motion intuition.