Calculating the magnetic field of the infinite solenoid and understanding the Ampere circuital law from the magnetic field of moving charges

The magnetic field of the infinite solenoid is calculated using a new method. An infinitely long charged line moving along a closed curve on the plane perpendicular to the infinite line will generate an electric current and so the magnetic field of the infinite solenoid. Through the electric–magnetic field relation, the magnetic field of the infinite solenoid is simply obtained and the reason why the magnetic field is a constant is clearly shown. Further, Ampere's circuital law is analyzed from the particle point of view using the electric–magnetic field relation. These discussions are helpful to the understanding of the magnetic field of the infinite solenoid and Ampere's circuital law for students and teachers of electromagnetism.