Champs magnétiques

A magnetic field is an invisible vector field represented by the symbol B, measured in tesla (T). All magnets have a magnetic field around them. Oersted demonstrated that a current-carrying conductor creates a magnetic field in surrounding space. The field strength decreases with distance from its source.

A moving charge experiences a magnetic force described by the cross-product of velocity and magnetic field vectors. The force magnitude depends on the charge amount, particle speed, and magnetic field strength. The force direction is perpendicular to both velocity and field, determined using the right-hand rule.

The right-hand rule determines magnetic force direction on a moving charge. Point your fingers in the velocity direction, curl them toward the magnetic field direction, and your thumb points in the force direction. This method provides a consistent way to find force orientation without calculation.

Static charges produce only electric fields that do not affect magnets. Magnetic force only occurs when charges move relative to a magnetic field. When charges are stationary, there is no magnetic force, but moving charges create magnetic fields that exert forces on other magnets.

The Lorentz force is the vector sum of electric and magnetic forces acting on a charged particle. It represents the total electromagnetic force experienced by a moving charge in combined electric and magnetic fields. This unified concept shows how electric and magnetic forces interact.

The SI unit for magnetic field strength is the tesla (T), named after inventor Nikola Tesla. The gauss (G) is a common non-SI unit. One tesla equals 10,000 gauss, providing a conversion factor between these measurement systems used in physics applications.

The magnetic force magnitude depends on the angle between velocity and magnetic field vectors. Maximum force occurs when velocity is perpendicular to the field. The force magnitude is calculated as F = QvB sin(θ), where θ is the angle between the vectors.