Consider the following image: A proton enters a magnetic field at right angles to it, as shown above. The direction of force acting on the proton will be

The direction of the magnetic force on a moving charged particle is determined by the Lorentz force law and the Right-Hand Rule. A proton is a positively charged particle. According to the Right-Hand Rule, if you point your right thumb in the direction of the velocity (v) and your index finger in the direction of the magnetic field (B), your palm or middle finger points in the direction of the force (F). In the provided scenario, the proton moves from left to right (velocity) and the magnetic field is directed from top to bottom. Applying the rule: thumb to the right, index finger down, the palm points into the page. This force acts at right angles to both the velocity and the magnetic field. Therefore, the force acting on the proton is directed into the page.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 12: Magnetic Effects of Electric Current > EXERCISES > p. 207