Definition of magnetic induction
The electric field force that the electric charge receives in the electric field is constant, and the direction is the same as or opposite to the electric field direction at that point. The magnetic field force (amperance) of a current in a magnetic field is related to the direction in which the current is placed in the magnetic field. When the current direction is parallel to the direction of the magnetic field, the amperage of the current is minimal, equal to zero; when the current direction and the magnetic field direction When vertical, the current is most affected by the ampere.
The point charge q is subjected to the force f when the velocity v moves in the magnetic field. Under the given conditions of the magnetic field, the magnitude of f is related to the direction of charge motion. When v is in or opposite to a particular direction, the force is zero; when v is perpendicular to this particular direction, the force is maximum, which is Fm. Fm is proportional to |q| and v. The ratio is independent of the motion charge, reflecting the nature of the magnetic field itself, defined as the magnitude of the magnetic induction, ie. The direction of B is defined as the direction in which the right hand spiral advances when the direction of the maximum force Fm of the positive charge is turned toward the direction of charge motion v. After B is defined, the force of the moving charge in the magnetic field B can be expressed as F = QVB, which is the Lorentz force formula.