A positively charged particle projected towards west is deflected towards north by a magnetic field. The direction of the magnetic field is

The direction of the magnetic force on a moving charged particle is determined by the Right-Hand Rule. For a positively charged particle, the thumb points in the direction of velocity (v) and the fingers point in the direction of the magnetic field (B); the palm then indicates the direction of the magnetic force (F). In this scenario, the particle is moving towards the West (thumb) and is deflected towards the North (palm). To satisfy this orientation using the right hand, the fingers must point vertically upwards. Mathematically, the Lorentz force is given by F = q(v × B). If velocity is along the negative x-axis (West) and the force is along the positive y-axis (North), the magnetic field must be along the positive z-axis (Upward) to satisfy the cross-product direction for a positive charge.