Definition and calculation formula of magnetic induction intensity

The electric field force that the electric charge is subjected to in the electric field is certain, and the direction is the same or opposite to the electric field direction of the point. The magnetic field force (Ampere force) that the current is subjected to somewhere in the magnetic field is related to the direction in which the current is placed in the magnetic field. When the direction of the current is parallel to the direction of the magnetic field, the ampere force on the current is the smallest, which is equal to zero; when the direction of the current is parallel to the direction of the magnetic field When it is vertical, the ampere force of the current is the largest.

A point charge q is acted upon by a force f as it moves with a velocity v in a magnetic field. Under the conditions of a given magnetic field, the size of f is related to the direction of charge movement. When v is along a special direction or opposite to it, the force is zero; when v is perpendicular to this special direction, the force is the largest, which is Fm. Fm is proportional to |q| and v, the ratio has nothing to do with the moving charge, and reflects the nature of the magnetic field itself, which is defined as the magnitude of the magnetic induction, ie. The direction of B is defined as: when the direction of the maximum force Fm on the positive charge turns to the direction of charge motion v, the direction of the right-handed spiral. After B is defined, the force on the moving charge in the magnetic field B can be expressed as F= QVB, which is the Lorentz force formula.

Calculation Formula:

In addition to using the Lorentz force to define B, B can also be defined according to the ampere force df=Idl×B on the current element Idl in the magnetic field, or according to the torque M=m×B on the magnetic moment m in the magnetic field B, three definitions, the methods are the same, and they are completely equivalent.

B=F/IL=F/qv=Φ/S

F: Lorentz force or Ampere force;

q: charge amount;

v: speed;

E: electric field strength;

Φ (=ΔBS or BΔS, B is the magnetic induction intensity, S is the area): magnetic flux;

S: area;

L: The length of the conductor in the magnetic field.

Definition: F=ILB.

Expression: B=F/IL.