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
Induction coil radio transmitters, arc lighting and quack medical electrotherapy devices from the 1880s to the 1920s. Today its only common use is as the ignition coils in internal combustion engines and in physics education to demonstrate induction. An induction coil consists of two coils of insulated wire wound around a common iron core "(M)". One coil, called the "primary winding" "(P)", is made from relatively few (tens or hundreds) turns of coarse wire. The other coil, the "secondary winding," "(S)" typically consists of many (thousands) turns of fine wire. An electric current is passed through the primary, creating a magnetic field.