Giroraio de Larmor
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Larmor radius is the radius of curvature of a charged particle's circular path in a magnetic field. Calculated using rL = (m·v⊥)/(q·B), where m is mass, v⊥ is perpendicular velocity, q the charge, and B the magnetic field strength. This formula derives from the Lorentz force acting as a centripetal force.
This calculation is essential in plasma physics, particle accelerators, and astrophysics. For instance, it helps predict solar wind particle trajectories in Earth's magnetic field. It's also used in fusion reactors to analyze ion motion in magnetic confinement.
Important considerations: 1) The formula requires only the perpendicular velocity component (v⊥). 2) Units must be consistent (SI: kg, m/s, C, T). 3) Relativistic effects are not included; adjustments are needed for velocities near light speed.
Frequently asked questions
Why is perpendicular velocity used in the formula?
The perpendicular component (v⊥) is critical because the magnetic force acts solely in this direction, causing circular motion, while the parallel component results in linear movement.
What units should I use for parameters?
Use SI units: kilograms (kg) for mass, coulombs (C) for charge, teslas (T) for magnetic field, and meters per second (m/s) for velocity.
What are real-world applications of this calculation?
It's used in aurora studies, plasma confinement in fusion reactors, and particle analysis in accelerators.
Does the calculation account for relativistic effects?
No. For velocities near light speed (10^8 m/s), relativistic adjustments are required.
How to handle negative charges?
Use the absolute value of charge (q). The sign doesn't affect the radius, only the rotation direction.