What are magnetic fields and how do they interact with charged particles?

Magnetic fields are regions of space where magnetic forces are experienced by magnetic materials or charged particles.

Magnetic fields are created by moving charges or magnetic materials. The strength of the magnetic field is proportional to the current or magnetic moment of the source. Magnetic fields can be visualised using magnetic field lines, which indicate the direction and strength of the field. The direction of the field is from north to south outside the magnet and from south to north inside the magnet.

Charged particles interact with magnetic fields through the Lorentz force. The Lorentz force is perpendicular to both the magnetic field and the velocity of the charged particle. It causes the particle to move in a circular path, known as a cyclotron motion. The radius of the circular path is proportional to the velocity and the strength of the magnetic field. This is the principle behind the operation of cyclotrons and other particle accelerators.

The interaction between magnetic fields and charged particles has many applications in physics and engineering. It is used in electric motors, generators, MRI machines, and particle accelerators. Magnetic fields also play a crucial role in the behaviour of the Earth's magnetic field, the aurora borealis, and the Van Allen radiation belts. Understanding the properties and behaviour of magnetic fields is essential for many fields of science and technology.