4.5.115 - Charged-particle radius in a magnetic field

Derive and use r = mv/(BQ) for the radius of a charged particle moving perpendicular to a magnetic field.

Use - charged-particle radius in a magnetic field to connect the rule to the data and decision in the question.

This matters because - charged-particle radius in a magnetic field determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply - charged-particle radius in a magnetic field to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: - Charged-particle radius in a magnetic field is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.