Electric_generator - Wikiparency

# Electric generator An **electric generator** converts mechanical power into electrical power by electromagnetic induction: when the magnetic flux through a coil changes, an electromotive force is induced in it, emf = −dΦ/dt (Faraday's law). A coil turning in a steady field produces an alternating voltage, emf = NBAω sin ωt.[^up2-13] In a [[Hydroelectricity|hydroelectric]] station the generator sits on the same shaft as the [[Water_turbine|water turbine]], and the grid frequency fixes how fast it must turn: frequency equals the number of poles times the speed in rpm divided by 120, so a slow hydro runner needs many poles to make 60 Hz. <div class="microsim-player"> <iframe src="https://wikitube-3d-microsims.netlify.app/Electric_generator.html" width="100%" height="620" frameborder="0" loading="lazy" sandbox="allow-scripts allow-same-origin" allow="accelerometer; gyroscope" title="Electric generator — p5.js microsim"></iframe> </div> *Microsim (THY-106): spin the rotor and add poles; the frequency readout shows when the machine is in step with a 60 Hz grid. ILLUSTRATIVE: the voltage amplitude is normalized to its 60 Hz value.* Videos: [16:9](https://wikitube-3d-microsims.netlify.app/media/Electric_generator_16x9.mp4) · [9:16](https://wikitube-3d-microsims.netlify.app/media/Electric_generator_9x16.mp4) ## Terminology A generator's rotating part is the rotor and its stationary part the stator; the winding in which the useful voltage is induced is the armature, and the field is set up either by permanent magnets or by field windings carrying direct current. Machines producing direct current are often called dynamos, and those producing alternating current alternators. ## History Michael Faraday's experiments of 1831 showed that a changing magnetic field induces an emf, and that moving a magnet relative to a coil produces a voltage only while it moves.[^up2-13] Practical dynamos followed in the next decades and were soon coupled to water wheels: on September 5, 1882, five Brush dynamos driven by a waterwheel on Upton Island below St. Anthony Falls in Minneapolis sent current to arc lamps on Washington Avenue.[^mnopedia1882] ### Direct current generators Early generators used a commutator to rectify the alternating emf of a rotating coil into direct current, as the Brush dynamos in Minneapolis did for arc lighting.[^mnopedia1882] ### Synchronous generators (alternating current generators) Large power-station generators are synchronous machines: a rotor carrying field poles turns inside a stator winding, and the machine's frequency is locked to its speed by f = p·n/120 for p poles at n rpm. A two-pole machine makes 60 Hz at 3,600 rpm; a hydro generator turning at 200 rpm needs 36 poles. ## Specialised types of generator Generators are distinguished by the current they produce and by how their field is supplied. ### Direct current (DC) DC generators use commutators or rectifiers; they have largely been replaced by alternators with electronic rectification. ### Alternating current (AC) AC generators include synchronous machines, which dominate central power stations, and induction generators, which are common in wind turbines. ## Common use cases Generators range from power-station machines of hundreds of megawatts to small portable sets and bicycle dynamos. ### Power station In hydroelectric, steam and gas-turbine plants the generator converts the turbine's shaft power to electricity with efficiencies above 90%; combined with an efficient water turbine, a hydroelectric unit delivers close to 90% of the water's potential energy as electricity.[^murphy-11] ## Equivalent circuit For analysis a generator is represented by an ideal source of emf in series with its internal impedance; the terminal voltage falls below the emf as current is drawn, and when the machine is used as a motor the induced back emf opposes the applied voltage.[^up2-13] ## See also - [[Hydroelectricity]] - [[Water_turbine]] - [[Alternating_current]] - [[Electric_motor]] ## References [^up2-13]: Ling, Samuel J.; Sanny, Jeff; Moebs, William (2016). *University Physics, Volume 2*, ch. 13 "Electromagnetic Induction" (§13.1 Faraday's law, p. 546; §13.6 Electric generators and back emf, p. 570). OpenStax. https://openstax.org/details/books/university-physics-volume-2 [^mnopedia1882]: Huber, Molly. "Hydroelectricity in Minneapolis, September 5, 1882." *MNopedia*, Minnesota Historical Society. https://www.mnhs.org/mnopedia/search/index/event/hydroelectricity-minneapolis-september-5-1882 [^murphy-11]: Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet*, ch. 11 "Hydroelectric Energy," pp. 173–181. eScholarship, University of California. https://escholarship.org/uc/item/9js5291m ### Portal Books - Ling, Sanny & Moebs (2016). *University Physics, Volume 2* — [OpenStax](https://openstax.org/details/books/university-physics-volume-2); on the [[PORTAL_Physics]] shelf. - Murphy, Tom W., Jr. (2021). *Energy and Human Ambitions on a Finite Planet* — [eScholarship](https://escholarship.org/uc/item/9js5291m); on the [[PORTAL_Energy]] shelf.  **Microsim — three.js (Wikitube framework):** *Electric generator* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/matter/Electric_generator.html" data-title="Electric generator"></div> *Built from `MICROSIM_GUIDE/specs/sims/Electric_generator.json`; part of the [[PORTAL_Matter|Matter portal]] spine (section sims and See-also variants).*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Electric_generator) : [Wikitube](https://en.wikitube.io/wiki/Electric_generator) · pinned revision [1352133178](https://en.wikipedia.org/w/index.php?oldid=1352133178) · 2026-09-10 ## Previous hub tags Hubs: `Life_Physics`, `Systems`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Energy]], [[PORTAL_Physics]]. --- *Thury station wave · 2026-09-10 · drafted · microsim THY-106 (p5.js) · parent [[Hydroelectricity]].*