Question

What is the SI unit and define magnetic field

Answer 1

A region in space where magnetic force is experienced is called Magnetic field.
The SI unit of magnetic field is tesla (T).

1 T is defined as the magnetic field in which a particle carrying a charge of 1 coulomb at a speed of 1 meter per second perpendicular to said field experiences a force with magnitude 1 newton, according to the Lorentz force law.