Magnetic field by that loop. Ampère's law is always valid for steady currents and can be used to calculate the -field for certain highly symmetric situations such as an infinite wire or an infinite solenoid. In a modified form that accounts for time varying electric fields, Ampère's law is one of four Maxwell's equations that describe electricity and magnetism. A charged particle moving in a -field experiences a "sideways" force that is proportional to the strength of the magnetic field, the component of the velocity that is perpendicular to the magnetic field and the charge of the particle. This force is known
Electromagnetic coil to which current is applied, which creates the magnetic field, is called the "primary winding". The other windings are called "secondary windings". Many electromagnetic coils have a magnetic core, a piece of ferromagnetic material like iron in the center to increase the magnetic field. The current through the coil magnetizes the iron, and the field of the magnetized material adds to the field produced by the wire. This is called a ferromagnetic-core or iron-core coil. A ferromagnetic core can increase the magnetic field and inductance of a coil by hundreds or thousands of times over what it would be without