Tesina in inglese sull'elettromagnetismo e i motori (2 pagine formato doc)
Magnetic forces exist around the Earth,in a region known as magnetosphere.Here is a mix of electrically charged particles,and its structure is determined by magnetic phenomena.
When currents flow through two parallel conductors,the magnetic fields of the conductors attract each other when the current flow is in the same direction in both conductors, and repel each other when the flows are in opposite directions.
When a current starts to flow in a conductor, a field moves out from the conductor itself and induces a current in it in the direction opposite to the original flow of current.
When a conductor is moved back and forth in a magnetic field, the flow of current in the conductor will change direction as often as the physical motion of the conductor changes direction.
Many devices generating electricity work on this principle,producing an oscillating form of current called “alternating current”.Alternating current (AC) is generally used as a source of electric power,both for industrial and domestic applications.. The voltage of AC may be changed to almost any value desired through a simple electromagnetic device called transformer.