For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by the Greek letter or Î½ (nu) (see e.g. Planck's formula).
An inductor, also called a coil or reactor, is a passive two-terminal electrical component that stores electrical energy in a magnetic field when electric current is flowing through it. An inductor typically consists of an electric conductor, such as a wire, that is wound into a coil. When the current flowing through an inductor changes, the time-varying magnetic field induces a voltage in the conductor, described by Faraday's law of induction. According to Lenz's law, the direction of induced electromotive force (e.m.f.) opposes the change in current that created it.
The adductor machine works the muscles on the inside of the thighs, particularly the adductor muscles. Their job is to bring the legs in, or adduct them, and to laterally rotate the thigh. The abductor machine works the gluteus medius, gluteus minimus, and gracilis.