In this paper, it is proposed that the magnetic field is an electric field that contracts in the direction of motion. This viewpoint is taken as the basic principle of analyzing the magnetic phenomena. The law of Lorentz force is proved by deduction, and any necessary correction is made. The law of electromagnetic induction is also proved by deduction, and the specific physical process of electromagnetic induction is clarified. The displacement current and Ampere circuit law is also proved by deduction. It is considered that the contraction of electric field in the direction of motion is the source of generation of magnetism, while the contraction of electric field in the direction of motion is fundamentally derived from the principle of constancy of light velocity. Since the magnetism has contributed the modern science and technology to the human beings, so it is convinced that the principle of constancy of light velocity is the most precious gift which the God has given to mankind. The motion with variable velocity of the electric field is also analyzed. It is pointed out that the generation of electric wave is essentially resulted from the distortion and contraction of the electric field caused by the propagation of the motion with variable velocity of the electron of the wave source at the velocity of light in its electric field. The electric field energy of the electric wave is propagated by the distortion of the electric field, while the magnetic field energy of the electric wave is propagated by the contraction of the electric field. The electric field energy is identically equal to the magnetic field energy. The electric field signal and the magnetic field signal are always in the same phase. The law of electromagnetic induction is derived from a distorted electric field. The common electromagnetic induction phenomenon is essentially a transmission and reception effect of electric waves. It is proved that the Ampere circuit law is derived from the displacement current, and that the displacement current is derived from the magnetic field, which is the electric field in motion. The propagation of electric wave is analyzed. It is pointed out that, if the propagation velocity of electric wave is greater than the velocity of light, the propagation effect of electric wave will be rapidly weakened. If the propagation velocity of electric wave is less than the velocity of light, the electromagnetic interference and radiation will be increased rapidly. Therefore, it is firmly believed that the actual velocity of light of about /s is the best propagation velocity of electric wave for mankind. It is considered that the actual velocity of light is another precious gift which the God has given to mankind.

magnetic field, electric field, special theory of relativity, lorentz force, electromagnetic induction, displacement current, principle of constancy of light velocity, electric wave