Overview of Magnetic Induction Strength

Magnetic induction refers to a physical quantity that describes the strength and direction of a magnetic field. It is a vector, commonly represented by the symbol B, and the international unit is Tesla (symbol T). Magnetic induction is also known as magnetic flux density or magnetic flux density. In physics, the strength of the magnetic field is represented by the magnetic induction intensity. The greater the magnetic induction intensity, the stronger the magnetic induction. The smaller the magnetic induction intensity, the weaker the magnetic induction.

There is a magnetic field around the current (moving charge), and its important external performance is: it has the effect of magnetic field force on the moving test charge, current-carrying conductor or permanent magnet introduced into the field, so the effect of the magnetic field on the moving test charge can be used to describe the magnetic field , and thus introduce the magnetic induction intensity B as the basic physical quantity to quantitatively describe the characteristics of each point in the magnetic field, and its status is equivalent to the electric field intensity E in the electric field. 

The reason why this physical quantity is called magnetic induction intensity, but not magnetic field intensity, is because the term magnetic field intensity has been used to represent another physical quantity in history. The difference: magnetic induction intensity reflects the interaction force, which is the two reference points A and B The stress relationship between the two, and the magnetic field strength is a unilateral quantity of the main body, regardless of whether the B side is involved or not, this quantity is unchanged.

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 velocity v in a magnetic field. Under the conditions of a given magnetic field, the magnitude 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, it reflects the nature of the magnetic field itself, and 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 received by the positive charge turns to the direction of charge motion v, the direction in which the right-handed spiral advances. After the definition of B, the force of the moving charge in the magnetic field B can be expressed as F= QVB, which is the Lorentz force formula.

In addition to defining B by the Lorentz force, 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.