< home >  3-15-2021   

   SOURCE:  http://www.tfcbooks.com/tesla/contents.htm   "TWENTY FIRST CENTURY BOOKS" >  http://www.tfcbooks.com/

Tesla's Writings
Table of Contents

  1. A New System of Alternate Current Motors and Transformers, AIEE Address, May 16, 1888 ( http://www.tfcbooks.com/tesla/1888-05-16.htm )
  2. Phenomena of Alternating Currents of Very High FrequencyElectrical World, Feb. 21, 1891
  3. The Tesla Effects With High Frequency and High Potential Currents, Introduction.--The Scope of the Tesla Lectures.
  4. Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891
  5. Experiments with Alternate Currents of High Potential and High Frequency, IEE Address, London, February 1892
  6. On Light and Other High Frequency Phenomena, Franklin Institute, Philadelphia, February 1893, and National Electric Light Association, St. Louis, March 1893
  7. On the Dissipation of the Electrical Energy of the Hertz ResonatorElectrical Engineer, Dec. 21, 1892
  8. Tesla's Oscillator and Other InventionsCentury Illustrated Magazine, April 1895
  9. Earth Electricity to Kill MonopolyThe World Sunday Magazine — March 8, 1896
  10. On ElectricityElectrical Review, January 27, 1897
  11. High Frequency Oscillators for Electro-therapeutic and Other PurposesElectrical Engineer, November 17, 1898
  12. Plans to Dispense With Artillery of the Present TypeThe Sun, New York, November 21, 1898
  13. Tesla Describes His Efforts in Various Fields of WorkElectrical Review - New York, November 30, 1898
  14. On Current InterruptersElectrical Review, March 15, 1899
  15. The Problem of Increasing Human EnergyCentury Illustrated Magazine, June 1900
  16. Tesla's New DiscoveryThe Sun, New York, January 30, 1901
  17. Talking With PlanetsCollier's Weekly, February 9, 1901 
  18. Inventor Tesla's Plant Nearing CompletionBrooklyn Eagle, February 8, 1902
  19. The Transmission of Electrical Energy Without WiresElectrical World, March 5, 1904
  20. Electric AutosManufacturers' Record, December 29, 1904
  21. The Transmission of Electrical Energy Without Wires as a Means for Furthering PeaceElectrical World and Engineer, January 7, 1905
  22. Tuned LightningEnglish Mechanic and World of Science, March 8, 1907
  23. Tesla's Wireless TorpedoNew York Times, March 19, 1907
  24. Possibilities of WirelessNew York Times, Oct. 22, 1907
  25. The Future of the Wireless ArtWireless Telegraphy & Telephony, Van Nostrand, 1908
  26. Mr. Tesla's VisionNew York Times, April 21, 1908
  27. Nikola Tesla's New WirelessThe Electrical Engineer - London, December 24, 1909
  28. Dr. Tesla Talks of Gas TurbinesMotor World, September 18,1911
  29. Tesla's New Monarch of MachinesNew York Herald, Oct. 15, 1911
  30. The Disturbing Influence of Solar Radiation On the Wireless Transmission of EnergyElectrical Review and Western Electrician, July 6, 1912
  31. How Cosmic Forces Shape Our DestiniesNew York American, February 7, 1915
  32. Some Personal RecollectionsScientific American, June 5, 1915
  33. The Wonder World To Be Created By ElectricityManufacturer's Record, September 9, 1915
  34. Nikola Tesla Sees a Wireless VisionNew York Times, Sunday, October 3, 1915
  35. Tesla's New Device Like Bolts of ThorNew York Times, December 8, 1915
  36. Wonders of the FutureCollier's Weekly, December 2, 1916
  37. Electric Drive for Battle ShipsNew York Herald, February 25, 1917
  38. Presentation of the Edison Medal to Nikola Tesla, May 8, 1917
  39. Tesla's Views on Electricity and the WarThe Electrical Experimenter, August 1917
  40. My InventionsElectrical Experimenter, February-June and October 1919
  41. Famous Scientific IllusionsElectrical Experimenter, February 1919
  42. The True WirelessElectrical Experimenter, May 1919
  43. Electrical OscillatorsElectrical Experimenter, July 1919
  44. Rain Can Be Controlled and Hydraulic Force Provided . . . , Syracuse Herald, ca. February 29, 1920
  45. When Woman is BossColliers, January 30, 1926
  46. World System of Wireless Transmission of EnergyTelegraph and Telegraph Age, October 16, 1927
  47. Nikola Tesla Tells of New Radio TheoriesNew York Herald Tribune, September 22, 1929
  48. Our Future Motive PowerEveryday Science and Mechanics, December 1931
  49. Tesla Cosmic Ray Motor May Transmit Power ‘Round EarthBrooklyn Eagle, July 10, 1932
  50. Pioneer Radio Engineer Gives Views On PowerNew York Herald Tribune, September 11, 1932
  51. The Eternal Source of Energy of the Universe, Origin and Intensity of Cosmic Rays, New York, October 13, 1932
  52. Tesla Invents Peace RayNew York Sun, July 10, 1934
  53. Tesla on Power Development and Future MarvelsNew York World Telegram, July 24, 1934
  54. Dr. Tesla Visions the End of Aircraft In WarEvery Week Magazine, October 21, 1934
  55. The New Art of Projecting Concentrated Non-dispersive Energy Through Natural Media, circa May 16, 1935
  56. A Machine to End WarLiberty, February 1935
  57. Tesla Predicts Ships Powered by Shore BeamNew York Herald Tribune, May 5, 1935
  58. Tesla Tries to Prevent World War IIProdigal Genius, 1944 — Unpublished Chapter 34   






https://www.tesla.com/blog/all-our-patent-are-belong-you <  Elon Musk on TESLA  

H Tesla-Machine-1907-tramsmit-Energy.JPG

Patents No. 649,621 ... 


Patents No 645,576... 


SOURCE: https://patentimages.storage.googleapis.com/8a/95/f3/1b1780c6941fb9/US1119732.pdf 

A  B  C  D  E  G  H  P 

Referring to the accompanying drawing, the figure is a view in elevation and part Section of an improved free terminal and  circuit of large surface with supporting structure and generating apparatus.

The terminal D consists of a suitably shaped metallic frame, in this case a ring of  nearly circular cross section, which is covered with half spherical metal plates P, thus constituting a very large conducting Surface, Smooth on all places where the electric charge principally accumulates. 

The frame is carried by a strong platform expressly provided for safety appliances, instruments of observation, etc., which in turn rests on insulating supports F

These should penetrate far into the hollow space formed by the terminal, and if the electric density at the points where they are bolted to the frame is still considerable, They may be specially protected by conducting hoods 
as H

A part of the improvements which form the subject of this specification, the transmitting circuit, in its general features, is identical with that described and claimed in my original Patents Nos. 645,576 and 649,621.


The circuit comprises a coil A which is in close inductive relation with a primary C, and one end of which is connected to a ground-plate E, while its other end is led through a separate self-induction coil B and 
a metallic cylinder B' to the terminal D.

 The connection to the latter should always be made at, or near the center, in order to secure a symmetrical distribution of the current, as otherwise, when the frequency is very high and the flow of large volume, the performance of the apparatus might be impaired. 

The primary C may be excited in  any desired manner,  from a suitable source of currents G, which may be an alternator or condenser, the important requirement being that the resonant condition is established, that is to say, that the terminal D is charged to the maximum pressure developed in the circuit, as I have specified in my original patents before referred to. 

 The adjustments should be made with particular care when the transmitter is one of great power, not only on account of economy, but also in order to avoid danger. 

 I have Shown that it is practicable to produce in a resonating circuit as  E A B B D  immense electrical activities, measured by tens and even hundreds of thousands of horse-power, and in such a case, if the points of maximum pressure should be shifted below the terminal D, along coil B, a ball of fire might break out and destroy the support F or any thing else in the way. 

For the better appreciation of the nature of this danger it  should be stated, that the destructive action may take place with inconceivable violence.

This will cease to be surprising when it is borne in mind, that the entire energy accumulated in the excited circuit, instead of requiring, as under normal working conditions, one quarter of the period or more for its transformation from static to kinetic form, may spend itself in an incomparably smaller interval of time, at
a rate of many 40 millions of horse power. 

The accident is apt to occur when, the transmitting circuit being strongly excited, the impressed oscillations upon it are caused, in any manner more or less sudden, to be more rapid than the free oscillations. 

It is therefore advisable to begin the adjustments with feeble and somewhat slower impressed oscillations,  strengthening and quickening them gradually, until the apparatus has been brought under perfect control. 

To increase the safety I provide on a convenient place, preferably on terminal D, one or more elements or plates either of somewhat Smaller radius of curvature or protruding more or less beyond the others (in which case they may be of larger radius of curvature) so that, should the pressure rise to a value, beyond which it is not desired to go, the powerful discharge may dart out there and lose itself harmlessly in the air. 

Such a plate, performing a function similar to that of a safety valve on a high pressure reservoir, is indicated at V

Still further extending the principles underlying my invention, special reference is made to coil B and conductor B'

The latter is in the form of a cylinder with smooth or polished surface of a radius much larger than that of the half spherical elements P , and widens out at the bottom into a hood H, which should be slotted to avoid loss by eddy currents and the purpose of which will be clear from the fore going. 

The coil B is wound on a frame or drum D of insulating material, with its turns close together. 

 I have discovered that when so wound the effect of the small radius of curvature of the wire itself is overcome 
and the coil behaves as a conductor of large radius of curvature, corresponding to that of the drum.

This feature is of considerable practical importance and is applicable  not only in this special instance, but generally. 

 For example, such plates at P P  of terminal D, though preferably of large radius of curvature, need not be necessarily so, for provided only that the individual plates or elements of a high potential conductor or terminal are arranged in proximity to each other and with their outer boundaries along an ideal symmetrical enveloping surface of a large radius of curvature, the advantages of the invention will  be more or less fully realized. 

The lower end of the coil B -which, if desired, may be extended up to the terminal D-should be somewhat below the uppermost turn of  coil A. 

This, I find, lessens the tendency of the charge to break out from the wire connecting both and to pass along the Support F (prime). 

Having described my invention, I claim: 



 hhhhhh  :::::  

Tesla-649-621-image-1of1.JPG  TeslA-Commutator.JPG Tesla-645-576-image-1of1.JPG   H



 hh  hhhhhhhh 


CONDUCTORS   (WORK  3-13-2021 )

    LIKE WATER BEING MOVED IN A TUB <  "magnetic flux" > 

"magnetic flux" https://en.wikipedia.org/wiki/Magnetic_flux



 https://www.youtube.com/watch?v=RjrQUyaImrc < VIDEO  < Motional emf   

 Electromagnetic Induction > Motional EMF : Change in Magnetic Flux induces EMF 

 1. Changing the area of the loop of conductive wire
 2. hhhhhhhhhhhhhhhhh
 3. hhhhhhhhhhhhhhhhhh

 Generating an EMF through a variation of the magnetic flux through the surface of a wire loop can be achieved in several ways:

1. the magnetic field B changes (e.g. an alternating magnetic field, or moving a wire loop towards a bar magnet where the B field is stronger),
2. the wire loop is deformed and the surface Σ changes, ( Changing the area of the loop of conductive wire)
3. the orientation of the surface dA changes (e.g. spinning a wire loop into a fixed magnetic field) 

 Q: Why does (A) a metal loop turning in an electric field [AND, (B)  an electic field moving in the presence of a metal loop]  produce a current ?

Both of these EMFs, despite their apparently distinct origins, are described by the same equation, namely, the EMF is the rate of change of magnetic flux through the wire.

 A: (1)When a conductor is moved through a magnetic field, the magnetic field exerts opposite forces on electrons and nuclei in the wire, and this creates the EMF. The term "motional EMF" is applied to this phenomenon, since the EMF is due to the motion of the wire.
(2) In other electrical generators, the magnets move, while the conductors do not. 
... In this case, the EMF is due to the electric force (qE) term in the Lorentz Force equation. The electric field in question is created by the changing magnetic field, resulting in an induced EMF, as described by the Maxwell–Faraday equation (one of the four modern Maxwell's equations).[28]

 induced an emf  
 SOURCE: https://en.wikipedia.org/wiki/Electromagnetic_field 
 SOURCE: https://en.wikipedia.org/wiki/Lorentz_force 
 "...  EMF
The magnetic force (qv × B) component of the Lorentz force is responsible for motional electromotive force (or motional EMF), the phenomenon underlying many electrical generators. When a conductor is moved through a magnetic field, the magnetic field exerts opposite forces on electrons and nuclei in the wire, and this creates the EMF. The term "motional EMF" is applied to this phenomenon, since the EMF is due to the motion of the wire.

In other electrical generators, the magnets move, while the conductors do not. In this case, the EMF is due to the electric force (qE) term in the Lorentz Force equation. The electric field in question is created by the changing magnetic field, resulting in an induced EMF, as described by the Maxwell–Faraday equation (one of the four modern Maxwell's equations).[28]

Both of these EMFs, despite their apparently distinct origins, are described by the same equation, namely, the EMF is the rate of change of magnetic flux through the wire. (This is Faraday's law of induction, see below.) Einstein's special theory of relativity was partially motivated by the desire to better understand this link between the two effects.[28] In fact, the electric and magnetic fields are different facets of the same electromagnetic field, and in moving from one inertial frame to another, the solenoidal vector field portion of the E-field can change in whole or in part to a B-field or vice versa.[29]  ..."



 2 Bar Magnet  https://www.intemag.com/permanent-magnets  

bar magnet is a permanent magnet 

 "Bar Magnet" "induced" "current"

  VIDEO >  https://www.youtube.com/watch?v=Ylgb8FFMgd4  <

 "the current will change its direction"
 "perpenicular to the magnetic field" 
 " How do we connect the coil to an external circuit?"
    avoid tangling
 " use brushes and slip-rings" 
  " so, basically we have two metallic rings" 
  " each ring is connected to ONE wire only"
  " these wires are also connected to carbon brushes - which is also conducting"
   "touching the rings - but not stuck to it"
    " when the coil starts rotating - the rings rotate along with the coil"
    " continuously changing its direction "Alternating Current" 

    "DC generator ... get rid of the "slip-rings"...
     "to maintain the current in the same direction...
    " the brushes change contacts - every half-rotation" 
    "automatically, by attaching "split-rings"...

    "an arrangement that automatically changes contacts ... called "commutator" 










"consumer" "transmission" "to transformer" connection to supply energy to the grid

"net metering"  to send power to DPL

"Intend primarily to offset part or all of your electricity requirements without the intention of generating excess power."

In twin letters copied to the Ohio Environmental Protection Agency, an attorney for AES Ohio Generation gives notice that “ownership and operation” of the J.M. Stuart ..."
 "... DPL prepares to sell two Adams County power plants
— DPL Inc. is preparing to sell two Adams County power plants it retired last year. In twin letters copied to the Ohio Environmental Protection Agency, an attorney for AES Ohio Generation gives notice that “ownership and operation” of the J.M. Stuart power station and the Killen power station will be transferred to Kingfisher Development Co., effective Friday. ... "


 SOURCE: https://energycentral.com/news/dpl-prepares-sell-two-adams-county-power-plants

 "...   NEWS
DPL prepares to sell two Adams County power plants
  Like Comment
Dec 17, 2019 7:37 am GMT 291 views
By: By Thomas Gnau, Dayton Daily News, Ohio

Dayton Daily News

Dec. 17--DPL Inc. is preparing to sell two Adams County power plants it retired last year.

In twin letters copied to the Ohio Environmental Protection Agency, an attorney for AES Ohio Generation gives notice that "ownership and operation" of the J.M. Stuart power station and the Killen power station will be transferred to Kingfisher Development Co., effective Friday.

The letters say AES intends to apply to the EPA to transfer the permits for both stations to Kingfisher, which has a Fenton, Mo. mailing address.

A spokeswoman for Dayton Power & Light Monday confirmed that the stations remained retired and that a sale is pending. She declined to offer further immediate details, saying an announcement is planned for Friday.

Kingfisher Development has the same street address as Aton Environmental, an environmental and real estate services company in Missouri. The company performs environmental assessments, among other services, for its clients.

A message seeking comment was sent to a representative of Aton.

Arlington, Va.-based AES Corp. owns DPL. DPL Inc.'s subsidiaries include Dayton Power and Light.

In May 2018, DPL said the two stations had been retired, in response to "declining market conditions."

While the plants operated, DP&L directly or indirectly employed nearly 700 people at the two coal-fired power plants.

J.M. Stuart station is a 1,755 megawatt facility co-owned by AES Ohio Generation, Vistra Energy and American Electric Power (AEP) with coal-fired and diesel-fired generating units.

Killen Station is a 618 megawatt facility co-owned by AES Ohio Gen and Vistra Energy with a coal-fired generating unit and combustion turbine.


(c)2019 the Dayton Daily News (Dayton, Ohio)

Visit the Dayton Daily News (Dayton, Ohio) at www.daytondailynews.com  ..."

 https://www.transmissionhub.com/wp-content/uploads/2018/12/MACH-Gen-FEB-27-2014-App.pdf < 8700+ pages 


 VIDEO >  https://www.youtube.com/watch?v=Ylgb8FFMgd4  


 electricity.html  < this page

   Electric generator (A.C. & D.C.) | Magnetic effects of current | Khan Academy   


































 "the current will change its direction"
 "perpenicular to the magnetic field" 
 " How do we connect the coil to an external circuit?"
    avoid tangling
 " use brushes and slip-rings" 
  " so, basically we have two metallic rings" 
  " each ring is connected to ONE wire only"
  " these wires are also connected to carbon brushes - which is also conducting"
   "touching the rings - but not stuck to it"
    " when the coil starts rotating - the rings rotate along with the coil"
    " continuously changing its direction "Alternating Current" 

    "DC generator ... get rid of the "slip-rings"...
     "to maintain the current in the same direction...
    " the brushes change contacts - every half-rotation" 
    "automatically, by attaching "split-rings"...

    "an arrangement that automatically changes contacts ... called "commutator" 



 solenoid  https://en.wikipedia.org/wiki/Solenoid   https://passive-components.eu/solenoids-explained/  



 Earth rotates between two magnetic poles  arrange copper on earth to create current harvest energy

- https://physics.aps.org/articles/v9/91
 "...  Chris Chyba of Princeton University and Kevin Hand of the Jet Propulsion Laboratory in Pasadena, California, saw a way forward.  ..."





 periodic Table  https://en.wikipedia.org/wiki/Periodic_table




 "...  a fundamental property of a material that quantifies how strongly it resists or conducts electric current.   ..."


 place conductor in magnetic field   "place conductor in a magnetic field" 


 SOURCE: http://physics.highpoint.edu/~jregester/potl/E&M/Magnetism/MagneticPolesFields.htm
Introduction    I assume at some point in your life you have played with magnets. The most basic kind is the bar magnet. If you hang a bar magnet so that it is free to pivot, it will turn so that one end points towards the north, more or less. This is the principle behind the compass, and the end of the magnet that indicates north is called the north pole of the magnet. The other end, logically enough, points south and is called the south pole.

... If two magnets are brought near each other, with like poles facing each other, they will repel; opposite poles attract.

... If you bend a bar magnet into a U shape, you have made a horseshoe magnet.

... Like an electric field, the magnetic field is a vector located at every point in space  ..."

  "bend" "magnet" "shape" "bar" "horseshoe"

 "magnet" "shape"

 "bar magnet" 



 Turning a conductor in a magnetic field produces q current 



 VIDEO >  https://www.youtube.com/watch?v=Ylgb8FFMgd4  <     

 commutator      https://en.wikipedia.org/wiki/Commutator_(electric)  

 split rings - https://en.wikipedia.org/wiki/Circle_cotter 

brushes - https://en.wikipedia.org/wiki/Brush_(electric)

slip rings  - https://en.wikipedia.org/wiki/Slip_ring

 eddy current

185.20 KB complete



AC-DV-Generator-Kahn-Academy-02-11sec.JPG  ----- turbine 

AC-DV-Generator-Kahn-Academy-03-18sec.JPG  ------- kinectic force (water) hitting turbine blades

AC-DV-Generator-Kahn-Academy-04-22sec.JPG -------- hydroElectric AND windturbine nacelle

AC-DV-Generator-Kahn-Academy-05-40sec.JPG < does NOT exist 

AC-DV-Generator-Kahn-Academy-04-40sec.JPG < ???????? WHY turn inside of a circle

AC-DV-Generator-Kahn-Academy-06-44sec.JPG  ------- making electric current begin

  home wall panel plug electrical receptacle home wall panel plug electrical power socket
      "transmission" "transformer" "electrical receptacle" "home" "wall" "power"
SOURCE: https://inspectapedia.com/electric/Electrical-Short-Circuits.php 
 "...  Where does Electricity in a Building Come From?
Sketch of electrical service to a home (C) Carson Dunlop Associates [ https://inspectapedia.com/electric/0500s.jpg ]

  The real source electrical power at most buildings is an electric utility company which operates an electrical generator (a power station). 
 The electric utility brings power from its power generators into a neighborhood where power is to be used by means of electrical transmission lines or power lines (big heavy wires). ... For efficiency, electrical power is usually delivered into a neighborhood at very high voltage levels. 
 In the neighborhood high voltage is converted by local power transformers (those big boxes or "cans" you see on some electric utility poles) to the  lower voltage levels (240V or 120V) used in most buildings. ... From the overhead (or in some communities buried) power transmission lines and transformer, a local power distribution wire (also overhead or buried) brings electrical power close to the building being served with power.

 IMAGE > ...the service entrance conductor  - service entry cable - "service drop" from utility pole     www.CarsonDunlop.com

  https://en.wikipedia.org/wiki/Service_drop  :: https://en.wikipedia.org/wiki/Weatherhead


... A service entry cable (SEC) (which is the responsibility of the building owner) connects the local power distribution wire to an electric meter mounted on or close to the building, and from the electrical meter, the service entry cable continues in to one or more main electrical panels on or inside the building. ... Sketch courtesy of Carson Dunlop Associates.

  [ SOURCE: https://www.thespruce.com/electrical-service-panel-basics-for-homeowners-1821532 ] 
"... What Is the Electrical Service Panel? ... The electric service panel is the connection between the external wires coming from the street and the internal wires of your home's electric system. The service panel is the central distribution point that connects the service wire or service drop—the main wire coming from the outside into the house—to the exit wires that split off and service different parts of the house. These exit wires are called branch circuits or branch wire circuits. ... In single-family residences, the owner of the building owns the electric service panel, not the electric company. Thus, the owner is responsible for all issues related to the electric service panel.
... Circuit Breaker Service Panels and Fuse Boxes... ...Electric service panels have a number of different names: fuse box, fuse panel, circuit breaker panel. Today, most homes have what is officially called the "electrical service panel", or simply, the service panel. A circuit breaker panel is not exactly the same as the fuse box ; because, it has mechanical, toggle-switch circuit breakers, not fuses, but it does perform the same function. The older fuses screw or pull in or out, as opposed to the rocker-style method of installing and removing circuit breakers.
... All of your home's power is located in the service panel. The electrical service panel provides 100, 200, or more amps of power to a home. Homes built between 1950 and 1965 may have these 60-ampere fuse boxes, often with four fuses. 
... Power comes into the house from a service drop, connects to the service lugs within the service panel, and is split into separate circuits throughout the house.  ..."

 [  ... Power comes into the house from a service drop, connects to the service lugs within the service panel, and is split into separate circuits throughout the house.  ..."  ] "Electric service drop", connects to the"service lug" within the service panel

1. This booklet is issued by Horry Electric Cooperative, Inc. (HEC) as a guide for obtaining and installing electric service.
It contains information on the types of electric service available, conditions for service, the standards for material and
construction in regards to the Member’s service entrance installation  ..."

... The electrical panel provides a place for mounting of fuses or circuit breakers which protect the building wiring from overheating and short circuits as a way to reduce fire risk. Inside of a building electrical power is distributed to various rooms through individual circuits, each of which is fed from the electrical panel(s).

However, for practical purposes, the source of electricity at an individual home or other building may be thought of as the circuit breaker panel or fuse box from which electrical power is distributed throughout a home or other building. Junction boxes and wall outlets may be thought of as secondary sources of electrical power since they convenient points at which a building occupant can connect electrical devices anywhere in a building.

See ELECTRICAL DEFINITIONS for definitions of "Volts", Watts, Amps, etc.  ..."

AC-DV-Generator-Kahn-Academy-07-48sec.JPG  ---------------- Electromagnetic-Induction 

AC-DV-Generator-Kahn-Academy-08-52sec.JPG -------------- Michael Faraday  Electromagnetic-Induction  

AC-DV-Generator-Kahn-Academy-09-54sec.JPG  ------------ Field lines North & South 

AC-DV-Generator-Kahn-Academy-10-58sec.JPG  -------- field lines , introduce object 

AC-DV-Generator-Kahn-Academy-11-111sec.JPG  -------- field lines , introduce conductor LOOP  

AC-DV-Generator-Kahn-Academy-12-121sec.JPG -------- field lines, conductor LOOP - FLOW arrow 

AC-DV-Generator-Kahn-Academy-13-123sec.JPG -------- slip-rings brush contacts UNKNOWN?

AC-DV-Generator-Kahn-Academy-14-132sec.JPG  ------ bulb blue  ELECTRIC GENERATORS (label) 

AC-DV-Generator-Kahn-Academy-15-138sec.JPG ----- bulb yellow   ELECTRIC GENERATORS (label)

AC-DV-Generator-Kahn-Academy-16-144sec.JPG  ----- right hand Rule - current direction

AC-DV-Generator-Kahn-Academy-17-351sec.JPG  ----  right hand Rule - current direction (two hands) 

AC-DV-Generator-Kahn-Academy-18-366sec.JPG  ---- UP, into screen  DOWN, out of screen 

AC-DV-Generator-Kahn-Academy-19-409sec.JPG ---- UP, into screen  DOWN, out of screen (with arrows ) 

AC-DV-Generator-Kahn-Academy-20-466sec.JPG ----- direct connect of bulb to circuit  1 of 3

AC-DV-Generator-Kahn-Academy-21-638sec.JPG ----- direct connect of bulb to circuit  2 of 3

 AC-DV-Generator-Kahn-Academy-27-645sec-connected-directly-tangling.JPG  --------------------- ADD 

AC-DV-Generator-Kahn-Academy-22-657sec.JPG ----- direct connect of bulb to circuit  3 of 3 
  AC-DV-Generator-Kahn-Academy-28-703sec-brushes-AND-slipRings.JPG  -----------------------ADD 

AC-DV-Generator-Kahn-Academy-23-704sec.JPG ------ add slip-rings brush contacts  1 of 2

AC-DV-Generator-Kahn-Academy-24-918sec.JPG -----  add slip-rings brush contacts  2 of 2 

AC-DV-Generator-Kahn-Academy-25-1125sec.JPG ---- "split-rings" appear 

 AC-DV-Generator-Kahn-Academy-29-1131sec-split-rings.JPG  --------------------------------- ADD 

AC-DV-Generator-Kahn-Academy-26-1227sec.JPG  ---------  "commutator"  D.C. GENERATOR 



 SOURCE:  Electricity PAGE   https://en.wikipedia.org/wiki/Electricity

Electricity  ( From Wikipedia, the free encyclopedia) [ with hyperlinking and comments added by Susan ]

Multiple lightning strikes on a city at night

Lightning is one of the most dramatic effects of electricity.

Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge.

Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations.

The presence of an electric charge, which can be either positive or negative, produces an electric field.

The movement of electric charges is an electric current and produces a magnetic field.

When a charge is placed in a location with a non-zero electric field, a force will act on it.

The magnitude of this force is given by Coulomb's law.

If the charge moves, the electric field would be doing work on the electric charge.

Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts.

Electricity is at the heart of many modern technologies, being used for:

Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries.

The theory of electromagnetism was developed in the 19th century, and by the end of that century electricity was being put to industrial and residential use by electrical engineers.

The rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution.

Electricity's extraordinary versatility means it can be put to an almost limitless set of applications which include transportheatinglightingcommunications, and computation.

Electrical power is now the backbone of modern industrial society.[1]



A bust of a bearded man with dishevelled hair < Thales 

Thales of Miletus (/ˈθeɪliːz/ THAY-leezGreekΘαλῆς (ὁ Μιλήσιος), Thalēsc. 624/623  – c. 548/545 BC) was a Greek mathematicianastronomer and pre-Socratic philosopher from Miletus in IoniaAsia Minor. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded him as the first philosopher in the Greek tradition,[1][2] and he is otherwise historically recognized as the first individual in Western civilization known to have entertained and engaged in scientific philosophy.[3][4] ...Thales is recognized for breaking from the use of mythology to explain the world and the universe, and instead explaining natural objects and phenomena by naturalistic theories and hypotheses, in a precursor to modern science. Almost all the other pre-Socratic philosophers followed him in explaining nature as deriving from a unity of everything based on the existence of a single ultimate substance, instead of using mythological explanations. Aristotle regarded him as the founder of the Ionian School and reported Thales' hypothesis that the originating principle of nature and the nature of matter was a single material substancewater.[5] ...In mathematics, Thales used geometry to calculate the heights of pyramids and the distance of ships from the shore. He is the first known individual to use deductive reasoning applied to geometry, by deriving four corollaries to Thales' theorem. He is the first known individual to whom a mathematical discovery has been attributed.[6]

Thales, the earliest known researcher into electricity

Long before any knowledge of electricity existed, people were aware of shocks from electric fish
https://en.wikipedia.org/wiki/Ancient_Egypt ]
Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish.
Electric fish were again reported millennia later by ancient GreekRoman and Arabic naturalists and physicians.[2] Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by electric catfish and electric rays, and knew that such shocks could travel along conducting objects.[3] 
Patients suffering from ailments such as gout or headache were directed to touch "electric fish" in the hope that the powerful jolt might cure them.[4]

Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. 

 [ Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. ]

Galvanic cell

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Galvanic cell with no cation flow

galvanic cell or voltaic cell, named after the scientists Luigi Galvani and Alessandro Volta, respectively, is an electrochemical cell in which an electric current is generated from spontaneous redox reactions. A common apparatus generally consists of two different metals, each immersed in separate beakers containing their respective metal ions in solution that are connected by a salt bridge (or separated by a porous membrane).[1]

Volta was the inventor of the voltaic pile, the first electrical battery. In common usage, the word "battery" has come to include a single galvanic cell, but a battery properly consists of multiple cells.[2]

Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.[5][6][7][8] 

Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe3O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself.[5][6] It is the most magnetic of all the naturally occurring minerals on Earth.[5][7] Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.[8]

Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak.[5] Small grains of magnetite are very common in igneous and metamorphic rocks.[9]

The chemical IUPAC name is iron(II,III) oxide and the common chemical name is ferrous-ferric oxide.[10]

Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature.[9]

A half-length portrait of a bald, somewhat portly man in a three-piece suit.

Benjamin Franklin conducted extensive research on electricity in the 18th century, as documented by Joseph Priestley (1767History and Present Status of Electricity, with whom Franklin carried on extended correspondence. [ https://publictrustdc.tumblr.com/post/87435975023/benjamin-franklin-benjamin-franklin-january-17/amp ]

Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.[5] [ https://en.wikipedia.org/wiki/De_Magnete ]

https://en.wikipedia.org/wiki/Etymology_of_electricity  ]
He ( William Gilbert ) coined the New Latin word electricus ("of amber" or "like amber", from ἤλεκτρονelektron, the Greek word for "amber") to refer to the property of attracting small objects after being rubbed.[10] ... This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646.[11]

Further work was conducted in the 17th and early 18th centuries by:

 Otto von Guericke, May 1686 https://en.wikipedia.org/wiki/Otto_von_Guericke
 Robert Boyle, January 1627 https://en.wikipedia.org/wiki/Robert_Boyle 
Stephen Gray, December 1666 https://en.wikipedia.org/wiki/Stephen_Gray_(scientist)
and Charles François de Cisternay du Fay, September 1698  https://en.wikipedia.org/wiki/Charles_Fran%C3%A7ois_de_Cisternay_du_Fay

Otto von Guericke,
 Robert Boyle
Stephen Gray 
and C. F. du Fay.[12] 

Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky.[13] A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature.[14] He also explained the apparently paradoxical behavior[15] of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges.[12] 
https://www.wired.com/2017/01/the-physics-of-leyden-jars/  ] 

Half-length portrait oil painting of a man in a dark suit < Michael Faraday's discoveries formed the foundation of electric motor technology.

Michael Faraday FRS (/ˈfærədeɪ, -di/; 22 September 1791 – 25 August 1867) was an English scientist who contributed to the study of electromagnetism and electrochemistry.
 His main discoveries include the principles underlying:

1) electromagnetic induction,
2) diamagnetism 
and 3) electrolysis

Although Faraday received little formal education, he was one of the most influential scientists in history.[1] It was by his research on the magnetic field around a conductor carrying a direct current that Faraday established the basis for the concept of the electromagnetic field in physics.

In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles.[16][17]
Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used.[16][17] 
The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820.
 Michael Faraday invented the electric motor in 1821,
and Georg Ohm mathematically analysed the electrical circuit in 1827.[17] 

Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and 1862.[18]

While the early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as: Alexander Graham BellOttó BláthyThomas EdisonGalileo FerrarisOliver HeavisideÁnyos JedlikWilliam Thomson, 1st Baron KelvinCharles Algernon ParsonsWerner von SiemensJoseph SwanReginald FessendenNikola Tesla and George Westinghouse, electricity turned from a scientific curiosity into an essential tool for modern life.

In 1887, Heinrich Hertz[19]:843–44[20] discovered that electrodes illuminated with ultraviolet light create electric sparks more easily.
In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energizing electrons.
This discovery led to the quantum revolution.
Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect".[21] 
The photoelectric effect is also employed in photocells - such as can be found in solar panels - and this is frequently used to make electricity commercially.

The first solid-state device was the "cat's-whisker detector" first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with a solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect.[22] 

In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it.

Current flow can be understood in two forms: as negatively charged electrons, and as positively charged electron deficiencies called holes. These charges and holes are understood in terms of quantum physics. The building material is most often a crystalline semiconductor.[23][24]

Solid-state electronics came into its own with the emergence of transistor technology.

The first working transistor, a germanium-based point-contact transistor, was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947,[25] followed by the bipolar junction transistor in 1948.[26] 

These early transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis.[27]:168 

They were followed by the silicon-based MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor), invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959.[28][29][30] 
It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses,[27]:165,179 leading to the silicon revolution.[31] 

Solid-state devices started becoming prevalent from the 1960s, with the transition from vacuum tubes to semiconductor diodes, transistorsintegrated circuit (IC) chips, MOSFETs, and light-emitting diode (LED) technology.

The most common electronic device is the MOSFET,[29][32] which has become the most widely manufactured device in history.[33] 
Common solid-state MOS devices include microprocessor chips[34] and semiconductor memory.[35][36] 
 A special type of semiconductor memory is flash memory, which is used in USB flash drives and mobile devices, as well as solid-state drive (SSD) technology to replace mechanically rotating magnetic disc hard disk drive (HDD) technology.


Electric charge

Main article: Electric charge

See also: electronproton, and ion

A clear glass dome has an external electrode which connects through the glass to a pair of gold leaves. A charged rod touches the external electrode and makes the leaves repel.

Charge on a gold-leaf electroscope causes the leaves to visibly repel each other

The presence of charge gives rise to an electrostatic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity.[19]:457 A lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract.[19]

The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them.[37][38]:35 The electromagnetic force is very strong, second only in strength to the strong interaction,[39] but unlike that force it operates over all distances.[40] In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 1042 times that of the gravitational attraction pulling them together.[41]

Charge originates from certain types of subatomic particles, the most familiar carriers of which are the electron and proton. Electric charge gives rise to and interacts with the electromagnetic force, one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity, that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system.[42] Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire.[38]:2–5 The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.

The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin.[43] The amount of charge is usually given the symbol Q and expressed in coulombs;[44] each electron carries the same charge of approximately −1.6022×10−19 coulomb. The proton has a charge that is equal and opposite, and thus +1.6022×10−19  coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle.[45]

Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer.[38]:2–5

Electric current

Main article: Electric current

The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. Electric current can flow through some things, electrical conductors, but will not flow through an electrical insulator.[46]  [ "Protons" in motion  "current" https://aip.scitation.org/doi/10.1063/1.471979 ]

By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively charged electrons around an electric circuit, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons.[47] However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. 

 SOURCE:   http://web.engr.oregonstate.edu/~traylor/ece112/beamer_lectures/elect_flow_vs_conv_I.pdf  ( Electron Current vs. Conventional Current)

In 1752, prior to electricity being identified with the electron, Ben Franklin chose a convention regarding the direction of current flow. Franklin assumed that positive charge carriers flowed from positive to negative terminals. We now know this is incorrect. In metals, the charge carrier is the electron whose charge is negative by definition (note negative sign): The flow of electrons is termed "electron current". Electrons flow from the negative terminal to the positive. "current flows from the positive terminal to the negative.


Conventional current or simply current, behaves as if positive charge carriers cause current flow. Conventional current flows from the positive terminal to the negative. Perhaps the clearest way to think about this is to pretend as if movement of positive charge carriers constituted current flow.

Figure 1: Electron Flow and Conventional Current Flow.  It is important to realize that the difference between conventional current flow and electron flow in no way effects any real-world behavior or computational results. In general, analyzing an electrical circuit yields results that are independent of the assumed direction of current flow.

Conventional current flow is the standard that most all of the world follows.


Two metal wires form an inverted V shape. A blindingly bright orange-white electric arc flows between their tips. < An electric arc provides an energetic demonstration of electric current

The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second,[38]:17 the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires.[48]

Current causes several observable effects, which historically were the means of recognizing its presence.

That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as electrolysis.

Their work was greatly expanded upon by Michael Faraday in 1833.

Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840.[38]:23–24 
One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass.[49] 

He had discovered electromagnetism, a fundamental interaction between electricity and magnetics. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference, which can be detrimental to the workings of adjacent equipment.[50]


In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative.[51]:11 [ As illustrated above ] If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. [ As illustrated above ]

Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sine wave.[51]:206–07 Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance.[51]:223–25 These properties however can become important when circuitry is subjected to transients, such as when first energised.

Electric field

Main article: Electric field

See also: Electrostatics

The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance.[40] However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker.[41]

Field lines emanating from a positive charge above a plane conductor

An electric field generally varies in space,[52] and its strength at any one point is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point.[19]:469–70 The conceptual charge, termed a 'test charge', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields. As the electric field is defined in terms of force, and force is a vector, having both magnitude and direction, so it follows that an electric field is a vector field.[19]:469–70

The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday,[53] whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines.[53] Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.[19]:479

A hollow conducting body carries all its charge on its outer surface. The field is therefore zero at all places inside the body.[38]:88 This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects.

The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre.[54] The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh.[55]

The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect[56]:155

Electric potential

Main article: Electric potential

See also: Voltage and Battery (electricity)

Two AA batteries each have a plus sign marked at one end.

A pair of AA cells. The + sign indicates the polarity of the potential difference between the battery terminals.

The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity.[19]:494–98 This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated.[19]:494–98 The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage.

For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable.[57]

Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field.[58] As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a conductor's surface, otherwise this would produce a force that will move the charge carriers to even the potential of the surface.

The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together.[38]:60


Main article: Electromagnets

A wire carries a current towards the reader. Concentric circles representing the magnetic field circle anticlockwise around the wire, as viewed by the reader.

Magnetic field circles around a current

Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it.[49] Ørsted's words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too.[59]

Ørsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère, who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart.[60] The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.[60]

A cut-away diagram of a small electric motor

The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current

This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained.[61]

Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction, enabled him to state the principle, now known as Faraday's law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy.[61] Faraday's disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work.


Italian physicist Alessandro Volta showing his "battery" to French emperor Napoleon Bonaparte in the early 19th century.

Main article: Electrochemistry

The ability of chemical reactions to produce electricity, and conversely the ability of electricity to drive chemical reactions has a wide array of uses.

Electrochemistry has always been an important part of electricity. From the initial invention of the Voltaic pile, electrochemical cells have evolved into the many different types of batteries, electroplating and electrolysis cells. Aluminium is produced in vast quantities this way, and many portable devices are electrically powered using rechargeable cells.

Electric circuits

Main article: Electric circuit

A basic electric circuit. The voltage source V on the left drives a current I around the circuit, delivering electrical energy into the resistor R. From the resistor, the current returns to the source, completing the circuit.

An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task.

The components in an electric circuit can take many forms, which can include elements such as resistorscapacitorsswitchestransformers and electronicsElectronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli.[62]:15–16

The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp.[62]:30–35

The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current, but instead blocks it.[62]:216–20

The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.[62]:226–29

Electric power

Main article: electric power

Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second.

Electric power, like mechanical power, is the rate of doing work, measured in watts, and represented by the letter P. The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is

{\displaystyle P={\text{work done per unit time}}={\frac {QV}{t}}=IV\,}


Q is electric charge in coulombs
t is time in seconds
I is electric current in amperes
V is electric potential or voltage in volts

Electricity generation is often done with electric generators, but can also be supplied by chemical sources such as electric batteries or by other means from a wide variety of sources of energy. Electric power is generally supplied to businesses and homes by the electric power industry. Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters, which keep a running total of the electric energy delivered to a customer. Unlike fossil fuels, electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency.[63]


Main article: electronics

Surface mount electronic components

Electronics deals with electrical circuits that involve active electrical components such as vacuum tubestransistorsdiodesoptoelectronicssensors and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible and electronics is widely used in information processingtelecommunications, and signal processing. The ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system.

Today, most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering.

Electromagnetic wave

Main article: Electromagnetic wave

Faraday's and Ampère's work showed that a time-varying magnetic field acted as a source of an electric field, and a time-varying electric field was a source of a magnetic field. Thus, when either field is changing in time, then a field of the other is necessarily induced.[19]:696–700 Such a phenomenon has the properties of a wave, and is naturally referred to as an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell's Laws, which unify light, fields, and charge are one of the great milestones of theoretical physics.[19]:696–700

Thus, the work of many researchers enabled the use of electronics to convert signals into high frequency oscillating currents, and via suitably shaped conductors, electricity permits the transmission and reception of these signals via radio waves over very long distances.

Production and uses (of electricity)

Generation and transmission

Main article: Electricity generation

See also: Electric power transmission and Mains electricity

Early 20th-century alternator made in BudapestHungary, in the power generating hall of a hydroelectric station (photograph by Prokudin-Gorsky, 1905–1915).

In the 6th century BC, the Greek philosopher Thales of Miletus experimented with amber rods and these experiments were the first studies into the production of electrical energy. While this method, now known as the triboelectric effect, can lift light objects and generate sparks, it is extremely inefficient.[64] It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the electrical battery, store energy chemically and make it available on demand in the form of electrical energy.[64] The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines.

Electrical power is usually generated by electro-mechanical generators driven by steam produced from fossil fuel combustion, or the heat released from nuclear reactions; or from other sources such as kinetic energy extracted from wind or flowing water.

The modern steam turbine invented by Sir Charles Parsons in 1884 today generates about 80 percent of the electric power in the world using a variety of heat sources.

Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends.[65] 

The invention in the late nineteenth century of the transformer meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient electrical transmission meant in turn that electricity could be generated at centralised power stations, where it benefited from economies of scale, and then be dispatched relatively long distances to where it was needed.[66][67]


A wind farm of about a dozen three-bladed white wind turbines.

Wind power is of increasing importance in many countries

Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required.[66] This requires electricity utilities [ en.wikipedia.org/wiki/Electric_utility ] to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations.

A certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses.

Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,[68] a rate of growth that is now being experienced by emerging economies such as those of India or China.[69][70] Historically, the growth rate for electricity demand has outstripped that for other forms of energy.[71]:16

Environmental concerns with electricity generation have led to an increased focus on generation from renewable sources, in particular from wind and solar. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.[71]:89


The light bulb, an early application of electricity, operates by Joule heating: the passage of current through resistance generating heat

Electricity is a very convenient way to transfer energy, and it has been adapted to a huge, and growing, number of uses.[72] 

The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power.

Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories.[73] 

Public utilities were set up in many cities targeting the burgeoning market for electrical lighting.

In the late 20th century and in modern times, the trend has started to flow in the direction of deregulation in the electrical power sector.[74]

The resistive Joule heating [ https://en.wikipedia.org/wiki/Joule_heating ]effect employed in filament light bulbs also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station.[75] A number of countries, such as Denmark, have issued legislation restricting or banning the use of resistive electric heating in new buildings.[76] Electricity is however still a highly practical energy source for heating and refrigeration,[77] with air conditioning/heat pumps representing a growing sector for electricity demand for heating and cooling, the effects of which electricity utilities are increasingly obliged to accommodate.[78]

Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. With the construction of first transcontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fibre and satellite communication have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process.

The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power.

A stationary motor such as a winch is easily provided with a supply of power, but a motor that moves with its application, such as an electric vehicle, is obliged to either carry along a power source such as a battery, or to collect current from a sliding contact such as a pantograph.

Electrically powered vehicles are used in public transportation, such as electric buses and trains,[79] and an increasing number of battery-powered electric cars in private ownership.

Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century,[80] and a fundamental building block of all modern circuitry.

A modern integrated circuit may contain several billion miniaturised transistors in a region only a few centimetres square.[81]

Electricity and the natural world

Physiological effects

Main article: Electric shock

A voltage applied to a human body causes an electric current through the tissues, and although the relationship is non-linear, the greater the voltage, the greater the current.[82] The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.1 mA to 1 mA for mains-frequency electricity, though a current as low as a microamp can be detected as an electrovibration effect under certain conditions.

[83] If the current is sufficiently high, it will cause muscle contraction, fibrillation of the heart, and tissue burns.[82] The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of torture. Death caused by an electric shock is referred to as electrocution. Electrocution is still the means of judicial execution in some jurisdictions, though its use has become rarer in recent times.[84]

Electrical phenomena in nature

Main article: Electrical phenomena

The electric eel, Electrophorus electricus

Electricity is not a human invention, and may be observed in several forms in nature, a prominent manifestation of which is lightning. Many interactions familiar at the macroscopic level, such as touchfriction or chemical bonding, are due to interactions between electric fields on the atomic scale. The Earth's magnetic field is thought to arise from a natural dynamo of circulating currents in the planet's core.[85] Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when subjected to external pressure.[86] This phenomenon is known as piezoelectricity, from the Greek piezein (πιέζειν), meaning to press, and was discovered in 1880 by Pierre and Jacques Curie. The effect is reciprocal, and when a piezoelectric material is subjected to an electric field, a small change in physical dimensions takes place.[86]

§Bioelectrogenesis in microbial life is a prominent phenomenon in soils and sediment ecology resulting from anaerobic respiration. The microbial fuel cell mimics this ubiquitous natural phenomenon.

Some organisms, such as sharks, are able to detect and respond to changes in electric fields, an ability known as electroreception,[87] while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon.[3] The order Gymnotiformes, of which the best known example is the electric eel, detect or stun their prey via high voltages generated from modified muscle cells called electrocytes.[3][4] All animals transmit information along their cell membranes with voltage pulses called action potentials, whose functions include communication by the nervous system between neurons and muscles.[88] An electric shock stimulates this system, and causes muscles to contract.[89] Action potentials are also responsible for coordinating activities in certain plants.[88]

Cultural perception

In 1850, William Gladstone asked the scientist Michael Faraday why electricity was valuable. Faraday answered, “One day sir, you may tax it.”[90]

In the 19th and early 20th century [1771 - 1939] , electricity was not part of the everyday life of many people, even in the industrialized Western world.

The popular culture of the time accordingly often depicted it as a mysterious, quasi-magical force that can slay the living, revive the dead or otherwise bend the laws of nature.[91] 

This attitude began with the 1771 experiments of Luigi Galvani in which the legs of dead frogs were shown to twitch on application of animal electricity. "Revitalization" or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work. These results were known to Mary Shelley when she authored Frankenstein (1819), although she does not name the method of revitalization of the monster. The revitalization of monsters with electricity later became a stock theme in horror films.

  "SONS OF MARTHA" - r. KIPLING  ::  http://www.kiplingsociety.co.uk/poems_martha.htm

As the public familiarity with electricity as the lifeblood of the Second Industrial Revolution grew, its wielders were more often cast in a positive light,[92] such as the workers who "finger death at their gloves' end as they piece and repiece the living wires" in Rudyard Kipling's 1907 poem Sons of Martha.[92] 

Electrically powered vehicles of every sort featured large in adventure stories such as those of Jules Verne and the Tom Swift books.[92] 

The masters of electricity, whether fictional or real—including scientists such as Thomas EdisonCharles Steinmetz or Nikola Tesla—were popularly conceived of as having wizard-like powers.[92]

With electricity ceasing to be a novelty and becoming a necessity of everyday life in the later half of the 20th century, it required particular attention by popular culture only when it stops flowing,[92] an event that usually signals disaster.[92] The people who keep it flowing, such as the nameless hero of Jimmy Webb’s song "Wichita Lineman" (1968),[92] are still often cast as heroic, wizard-like figures.[92]

 VIDEO OF SONG : https://www.youtube.com/watch?v=4qoymGCDYzU

See also


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