1820, the Dutch scientist Oster (1777 ~ 185 1) accidentally discovered that when the current was in the wire, the small magnetic needle on the side shifted. Oster's experiments all use a straight wire, and then experts roll the wire into an irregular shape and plug it in to study the magnetic field of current scientifically. There is a magnetic field around the patch cord.
The direction of magnetic field is related to the direction of current, which is called the magnetic effect of current. Electromagnetism, that is, current produces magnetism according to conductive electromagnetic coils, such as solenoid valves, is made through these principles; Magnetism generates electricity, even if the electromagnetic coil cuts the magnetic field lines, it will also generate current. For example, generator sets are made by these principles, and large hydropower plants use rotating magnetic fields.
The laser cuts hundreds of tons of electromagnetic coils in the internal structure, generates current, and then converts the voltage to send the electricity to far places. Electromagnetism means that according to the current passing through a straight metal wire, an annular magnetic field will be generated in the space around the wire. The more current flows through the wire, the stronger the magnetic field. The magnetic field is annular and closely surrounds the periphery of the wire.
The direction of the magnetic field can also be determined according to the "right-hand spiral law", also known as "Ampere's law 1": hold the straight wire with the left hand and let the thumb deviate from the current direction, so that the bending direction of the four fingers is the magnetic field direction. The magnetic field generated by this straight wire is actually similar to the effect of placing a circle of small magnets with NS poles connected end to end around the wire.