Why is the trajectory of the positively charged particle curving down, to the bottom of the screen, when moving in the magnetic field?

Because the force F is always at 90 degrees to the velocity of the particle.

Explanation:

The factors that determine the path of a particle in a uniform magnetic field depend on

The magnetic flux density

The charge on the particle

The speed of the particle

Why is the trajectory of the positively charged particle curving down, to the bottom of the screen, when moving in the magnetic field?

Because the force F is always at 90 degrees to the velocity of the particle.

This can be illustrated by the equation

F = BQVSINØ

The magnetic force is always acting perpendicular to the particle velocity and its direction can be found using the left hand rule.

the amount of current in the coil

d. air pressure decreases as altitude increases.