Chapter-4|Moving Charges and Magnetism| NCERT 12th Physics:
The toroid is a hollow circular ring on which a large number of insulated turns of a metallic wire are closely wound.
Toroid is used in devices such as synchrotron in which high magnetic field is required.
Note: Since there is no current is flowing inside or outside the toroid so there is no magnetic field (outside or inside).
So we have to calculate magnetic field at point P only.
Let I be the current, r be the mean radius, n be the number of turns per unit length and B be the Magnetic field inside the toroid.
The line integral of magnetic field around closed path of circle of radius r is-
Force on Moving Charge in a Uniform Magnetic Field:
In case of motion of charge in a magnetic field, the magnetic force is perpendicular to the velocity of the particle.