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An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. [2] For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. [3] Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used.
Dynamos and alternators require a source of power to drive their field coils. This could not be supplied by their own generator's output, without some process of ' bootstrapping '. Henry Wilde , an electrical engineer from Manchester, England, developed a combination of magneto and electro-magnet generator, where the magneto was used only to ...
Except for permanent magnet generators, a generator produces output voltage proportional to the magnetic flux, which is the sum of flux from the magnetization of the structure and the flux proportional to the field produced by the excitation current. If there is no excitation current the flux is tiny and the armature voltage is almost nil.
An early example of electromagnetic rotation was the first rotary machine built by Ányos Jedlik with electromagnets and a commutator, in 1826-27. [2] Other pioneers in the field of electricity include Hippolyte Pixii who built an alternating current generator in 1832, and William Ritchie's construction of an electromagnetic generator with four rotor coils, a commutator and brushes, also in 1832.
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal nĚ‚, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
The magnetic field lines are indicated, with their direction shown by arrows. The magnetic flux corresponds to the 'density of field lines'. The magnetic flux is thus densest in the middle of the solenoid, and weakest outside of it. Faraday's law of induction makes use of the magnetic flux Φ B through a region of space enclosed by a wire loop.
The rotating magnetic field is the key principle in the operation of induction machines.The induction motor consists of a stator and rotor.In the stator a group of fixed windings are so arranged that a two phase current, for example, produces a magnetic field which rotates at an angular velocity determined by the frequency of the alternating current.
The simplest type of linear alternator is the mechanically powered flashlight (shake type). This is a torch (UK) or flashlight (USA) which contains a coil and a permanent magnet . When the appliance is shaken back and forth, the magnet oscillates through the coil and induces an electric current .